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binutils-gdb/gdb/solib.c
Maciej W. Rozycki 3e29f34a4e MIPS: Keep the ISA bit in compressed code addresses 
1. Background information

The MIPS architecture, as originally designed and implemented in
mid-1980s has a uniform instruction word size that is 4 bytes, naturally
aligned.  As such all MIPS instructions are located at addresses that
have their bits #1 and #0 set to zeroes, and any attempt to execute an
instruction from an address that has any of the two bits set to one
causes an address error exception.  This may for example happen when a
jump-register instruction is executed whose register value used as the
jump target has any of these bits set.

Then in mid 1990s LSI sought a way to improve code density for their
TinyRISC family of MIPS cores and invented an alternatively encoded
instruction set in a joint effort with MIPS Technologies (then a
subsidiary of SGI).  The new instruction set has been named the MIPS16
ASE (Application-Specific Extension) and uses a variable instruction
word size, which is 2 bytes (as the name of the ASE suggests) for most,
but there are a couple of exceptions that take 4 bytes, and then most of
the 2-byte instructions can be treated with a 2-byte extension prefix to
expand the range of the immediate operands used.

As a result instructions are no longer 4-byte aligned, instead they are
aligned to a multiple of 2.  That left the bit #0 still unused for code
references, be it for the standard MIPS (i.e. as originally invented) or
for the MIPS16 instruction set, and based on that observation a clever
trick was invented that on one hand allowed the processor to be
seamlessly switched between the two instruction sets at any time at the
run time while on the other avoided the introduction of any special
control register to do that.

So it is the bit #0 of the instruction address that was chosen as the
selector and named the ISA bit.  Any instruction executed at an even
address is interpreted as a standard MIPS instruction (the address still
has to have its bit #1 clear), any instruction executed at an odd
address is interpreted as a MIPS16 instruction.

To switch between modes ordinary jump instructions are used, such as
used for function calls and returns, specifically the bit #0 of the
source register used in jump-register instructions selects the execution
(ISA) mode for the following piece of code to be interpreted in.
Additionally new jump-immediate instructions were added that flipped the
ISA bit to select the opposite mode upon execution.  They were
considered necessary to avoid the need to make register jumps in all
cases as the original jump-immediate instructions provided no way to
change the bit #0 at all.

This was all important for cases where standard MIPS and MIPS16 code had
to be mixed, either for compatibility with the existing binary code base
or to access resources not reachable from MIPS16 code (the MIPS16
instruction set only provides access to general-purpose registers, and
not for example floating-point unit registers or privileged coprocessor
0 registers) -- pieces of code in the opposite mode can be executed as
ordinary subroutine calls.

A similar approach has been more recently adopted for the MIPS16
replacement instruction set defined as the so called microMIPS ASE.
This is another instruction set encoding introduced to the MIPS
architecture.  Just like the MIPS16 ASE, the microMIPS instruction set
uses a variable-length encoding, where each instruction takes a multiple
of 2 bytes.  The ISA bit has been reused and for microMIPS-capable
processors selects between the standard MIPS and the microMIPS mode
instead.

2. Statement of the problem

To put it shortly, MIPS16 and microMIPS code pointers used by GDB are
different to these observed at the run time.  This results in the same
expressions being evaluated producing different results in GDB and in
the program being debugged.  Obviously it's the results obtained at the
run time that are correct (they define how the program behaves) and
therefore by definition the results obtained in GDB are incorrect.

A bit longer description will record that obviously at the run time the
ISA bit has to be set correctly (refer to background information above
if unsure why so) or the program will not run as expected.  This is
recorded in all the executable file structures used at the run time: the
dynamic symbol table (but not always the static one!), the GOT, and
obviously in all the addresses embedded in code or data of the program
itself, calculated by applying the appropriate relocations at the static
link time.

While a program is being processed by GDB, the ISA bit is stripped off
from any code addresses, presumably to make them the same as the
respective raw memory byte address used by the processor to access the
instruction in the instruction fetch access cycle.  This stripping is
actually performed outside GDB proper, in BFD, specifically
_bfd_mips_elf_symbol_processing (elfxx-mips.c, see the piece of code at
the very bottom of that function, starting with an: "If this is an
odd-valued function symbol, assume it's a MIPS16 or microMIPS one."
comment).

This function is also responsible for symbol table dumps made by
`objdump' too, so you'll never see the ISA bit reported there by that
tool, you need to use `readelf'.

This is however unlike what is ever done at the run time, the ISA bit
once present is never stripped off, for example a cast like this:

(short *) main

will not strip the ISA bit off and if the resulting pointer is intended
to be used to access instructions as data, for example for software
instruction decoding (like for fault recovery or emulation in a signal
handler) or for self-modifying code then the bit still has to be
stripped off by an explicit AND operation.

This is probably best illustrated with a simple real program example.
Let's consider the following simple program:

$ cat foobar.c
int __attribute__ ((mips16)) foo (void)
{
  return 1;
}

int __attribute__ ((mips16)) bar (void)
{
  return 2;
}

int __attribute__ ((nomips16)) foo32 (void)
{
  return 3;
}

int (*foo32p) (void) = foo32;
int (*foop) (void) = foo;
int fooi = (int) foo;

int
main (void)
{
  return foop ();
}
$

This is plain C with no odd tricks, except from the instruction mode
attributes.  They are not necessary to trigger this problem, I just put
them here so that the program can be contained in a single source file
and to make it obvious which function is MIPS16 code and which is not.

Let's try it with Linux, so that everyone can repeat this experiment:

$ mips-linux-gnu-gcc -mips16 -g -O2 -o foobar foobar.c
$

Let's have a look at some interesting symbols:

$ mips-linux-gnu-readelf -s foobar | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 7 entries:
Symbol table '.symtab' contains 95 entries:
    55: 00000000     0 FILE    LOCAL  DEFAULT  ABS foobar.c
    66: 0040068c     4 FUNC    GLOBAL DEFAULT [MIPS16]    12 bar
    68: 00410848     4 OBJECT  GLOBAL DEFAULT   21 foo32p
    70: 00410844     4 OBJECT  GLOBAL DEFAULT   21 foop
    78: 00400684     8 FUNC    GLOBAL DEFAULT   12 foo32
    80: 00400680     4 FUNC    GLOBAL DEFAULT [MIPS16]    12 foo
    88: 00410840     4 OBJECT  GLOBAL DEFAULT   21 fooi
$

Hmm, no sight of the ISA bit, but notice how foo and bar (but not
foo32!) have been marked as MIPS16 functions (ELF symbol structure's
`st_other' field is used for that).

So let's try to run and poke at this program with GDB.  I'll be using a
native system for simplicity (I'll be using ellipses here and there to
remove unrelated clutter):

$ ./foobar
$ echo $?
1
$

So far, so good.

$ gdb ./foobar
[...]
(gdb) break main
Breakpoint 1 at 0x400490: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb)

Yay, it worked!  OK, so let's poke at it:

(gdb) print main
$1 = {int (void)} 0x400490 <main>
(gdb) print foo32
$2 = {int (void)} 0x400684 <foo32>
(gdb) print foo32p
$3 = (int (*)(void)) 0x400684 <foo32>
(gdb) print bar
$4 = {int (void)} 0x40068c <bar>
(gdb) print foo
$5 = {int (void)} 0x400680 <foo>
(gdb) print foop
$6 = (int (*)(void)) 0x400681 <foo>
(gdb)

A-ha!  Here's the difference and finally the ISA bit!

(gdb) print /x fooi
$7 = 0x400681
(gdb) p/x $pc
p/x $pc
$8 = 0x400491
(gdb)

And here as well...

(gdb) advance foo
foo () at foobar.c:4
4       }
(gdb) disassemble
Dump of assembler code for function foo:
   0x00400680 <+0>:     jr      ra
   0x00400682 <+2>:     li      v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0  foo () at foobar.c:4
main () at foobar.c:24
24      }
Value returned is $9 = 1
(gdb) continue
Continuing.
[Inferior 1 (process 14103) exited with code 01]
(gdb)

So let's be a bit inquisitive...

(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb)

Actually we do not like to run foo here at all.  Let's run bar instead!

(gdb) set foop = bar
(gdb) print foop
$10 = (int (*)(void)) 0x40068c <bar>
(gdb)

Hmm, no ISA bit.  Is it going to work?

(gdb) advance bar
bar () at foobar.c:9
9       }
(gdb) p/x $pc
$11 = 0x40068c
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068c <+0>:     jr      ra
   0x0040068e <+2>:     li      v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0  bar () at foobar.c:9

Program received signal SIGILL, Illegal instruction.
bar () at foobar.c:9
9       }
(gdb)

Oops!

(gdb) p/x $pc
$12 = 0x40068c
(gdb)

We're still there!

(gdb) continue
Continuing.

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)

So let's try something else:

(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) set foop = foo
(gdb) advance foo
foo () at foobar.c:4
4       }
(gdb) disassemble
Dump of assembler code for function foo:
=> 0x00400680 <+0>:     jr      ra
   0x00400682 <+2>:     li      v0,1
End of assembler dump.
(gdb) finish
Run till exit from #0  foo () at foobar.c:4

Program received signal SIGILL, Illegal instruction.
foo () at foobar.c:4
4       }
(gdb) continue
Continuing.

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.
(gdb)

The same problem!

(gdb) run
Starting program:
/net/build2-lucid-cs/scratch/macro/mips-linux-fsf-gcc/isa-bit/foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) set foop = foo32
(gdb) advance foo32
foo32 () at foobar.c:14
14      }
(gdb) disassemble
Dump of assembler code for function foo32:
=> 0x00400684 <+0>:     jr      ra
   0x00400688 <+4>:     li      v0,3
End of assembler dump.
(gdb) finish
Run till exit from #0  foo32 () at foobar.c:14
main () at foobar.c:24
24      }
Value returned is $14 = 3
(gdb) continue
Continuing.
[Inferior 1 (process 14113) exited with code 03]
(gdb)

That did work though, so it's the ISA bit only!

(gdb) quit

Enough!

That's the tip of the iceberg only though.  So let's rebuild the
executable with some dynamic symbols:

$ mips-linux-gnu-gcc -mips16 -Wl,--export-dynamic -g -O2 -o foobar-dyn foobar.c
$ mips-linux-gnu-readelf -s foobar-dyn | egrep 'table|foo|bar'
Symbol table '.dynsym' contains 32 entries:
     6: 004009cd     4 FUNC    GLOBAL DEFAULT   12 bar
     8: 00410b88     4 OBJECT  GLOBAL DEFAULT   21 foo32p
     9: 00410b84     4 OBJECT  GLOBAL DEFAULT   21 foop
    15: 004009c4     8 FUNC    GLOBAL DEFAULT   12 foo32
    17: 004009c1     4 FUNC    GLOBAL DEFAULT   12 foo
    25: 00410b80     4 OBJECT  GLOBAL DEFAULT   21 fooi
Symbol table '.symtab' contains 95 entries:
    55: 00000000     0 FILE    LOCAL  DEFAULT  ABS foobar.c
    69: 004009cd     4 FUNC    GLOBAL DEFAULT   12 bar
    71: 00410b88     4 OBJECT  GLOBAL DEFAULT   21 foo32p
    72: 00410b84     4 OBJECT  GLOBAL DEFAULT   21 foop
    79: 004009c4     8 FUNC    GLOBAL DEFAULT   12 foo32
    81: 004009c1     4 FUNC    GLOBAL DEFAULT   12 foo
    89: 00410b80     4 OBJECT  GLOBAL DEFAULT   21 fooi
$

OK, now the ISA bit is there for a change, but the MIPS16 `st_other'
attribute gone, hmm...  What does `objdump' do then:

$ mips-linux-gnu-objdump -Tt foobar-dyn | egrep 'SYMBOL|foo|bar'
foobar-dyn:     file format elf32-tradbigmips
SYMBOL TABLE:
00000000 l    df *ABS*  00000000              foobar.c
004009cc g     F .text  00000004              0xf0 bar
00410b88 g     O .data  00000004              foo32p
00410b84 g     O .data  00000004              foop
004009c4 g     F .text  00000008              foo32
004009c0 g     F .text  00000004              0xf0 foo
00410b80 g     O .data  00000004              fooi
DYNAMIC SYMBOL TABLE:
004009cc g    DF .text  00000004  Base        0xf0 bar
00410b88 g    DO .data  00000004  Base        foo32p
00410b84 g    DO .data  00000004  Base        foop
004009c4 g    DF .text  00000008  Base        foo32
004009c0 g    DF .text  00000004  Base        0xf0 foo
00410b80 g    DO .data  00000004  Base        fooi
$

Hmm, the attribute (0xf0, printed raw) is back, and the ISA bit gone
again.

Let's have a look at some DWARF-2 records GDB uses (I'll be stripping
off a lot here for brevity) -- debug info:

$ mips-linux-gnu-readelf -wi foobar
Contents of the .debug_info section:
[...]
  Compilation Unit @ offset 0x88:
   Length:        0xbb (32-bit)
   Version:       4
   Abbrev Offset: 62
   Pointer Size:  4
 <0><93>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <94>   DW_AT_producer    : (indirect string, offset: 0x19e): GNU C 4.8.0 20120513 (experimental) -meb -mips16 -march=mips32r2 -mhard-float -mllsc -mplt -mno-synci -mno-shared -mabi=32 -g -O2
    <98>   DW_AT_language    : 1        (ANSI C)
    <99>   DW_AT_name        : (indirect string, offset: 0x190): foobar.c
    <9d>   DW_AT_comp_dir    : (indirect string, offset: 0x225): [...]
    <a1>   DW_AT_ranges      : 0x0
    <a5>   DW_AT_low_pc      : 0x0
    <a9>   DW_AT_stmt_list   : 0x27
 <1><ad>: Abbrev Number: 2 (DW_TAG_subprogram)
    <ae>   DW_AT_external    : 1
    <ae>   DW_AT_name        : foo
    <b2>   DW_AT_decl_file   : 1
    <b3>   DW_AT_decl_line   : 1
    <b4>   DW_AT_prototyped  : 1
    <b4>   DW_AT_type        : <0xc2>
    <b8>   DW_AT_low_pc      : 0x400680
    <bc>   DW_AT_high_pc     : 0x400684
    <c0>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <c2>   DW_AT_GNU_all_call_sites: 1
 <1><c2>: Abbrev Number: 3 (DW_TAG_base_type)
    <c3>   DW_AT_byte_size   : 4
    <c4>   DW_AT_encoding    : 5        (signed)
    <c5>   DW_AT_name        : int
 <1><c9>: Abbrev Number: 4 (DW_TAG_subprogram)
    <ca>   DW_AT_external    : 1
    <ca>   DW_AT_name        : (indirect string, offset: 0x18a): foo32
    <ce>   DW_AT_decl_file   : 1
    <cf>   DW_AT_decl_line   : 11
    <d0>   DW_AT_prototyped  : 1
    <d0>   DW_AT_type        : <0xc2>
    <d4>   DW_AT_low_pc      : 0x400684
    <d8>   DW_AT_high_pc     : 0x40068c
    <dc>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <de>   DW_AT_GNU_all_call_sites: 1
 <1><de>: Abbrev Number: 2 (DW_TAG_subprogram)
    <df>   DW_AT_external    : 1
    <df>   DW_AT_name        : bar
    <e3>   DW_AT_decl_file   : 1
    <e4>   DW_AT_decl_line   : 6
    <e5>   DW_AT_prototyped  : 1
    <e5>   DW_AT_type        : <0xc2>
    <e9>   DW_AT_low_pc      : 0x40068c
    <ed>   DW_AT_high_pc     : 0x400690
    <f1>   DW_AT_frame_base  : 1 byte block: 9c         (DW_OP_call_frame_cfa)
    <f3>   DW_AT_GNU_all_call_sites: 1
 <1><f3>: Abbrev Number: 5 (DW_TAG_subprogram)
    <f4>   DW_AT_external    : 1
    <f4>   DW_AT_name        : (indirect string, offset: 0x199): main
    <f8>   DW_AT_decl_file   : 1
    <f9>   DW_AT_decl_line   : 21
    <fa>   DW_AT_prototyped  : 1
    <fa>   DW_AT_type        : <0xc2>
    <fe>   DW_AT_low_pc      : 0x400490
    <102>   DW_AT_high_pc     : 0x4004a4
    <106>   DW_AT_frame_base  : 1 byte block: 9c        (DW_OP_call_frame_cfa)
    <108>   DW_AT_GNU_all_tail_call_sites: 1
[...]
$

-- no sign of the ISA bit anywhere -- frame info:

$ mips-linux-gnu-readelf -wf foobar
[...]
Contents of the .debug_frame section:

00000000 0000000c ffffffff CIE
  Version:               1
  Augmentation:          ""
  Code alignment factor: 1
  Data alignment factor: -4
  Return address column: 31

  DW_CFA_def_cfa_register: r29
  DW_CFA_nop

00000010 0000000c 00000000 FDE cie=00000000 pc=00400680..00400684

00000020 0000000c 00000000 FDE cie=00000000 pc=00400684..0040068c

00000030 0000000c 00000000 FDE cie=00000000 pc=0040068c..00400690

00000040 00000018 00000000 FDE cie=00000000 pc=00400490..004004a4
  DW_CFA_advance_loc: 6 to 00400496
  DW_CFA_def_cfa_offset: 32
  DW_CFA_offset: r31 at cfa-4
  DW_CFA_advance_loc: 6 to 0040049c
  DW_CFA_restore: r31
  DW_CFA_def_cfa_offset: 0
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
[...]
$

-- no sign of the ISA bit anywhere -- range info (GDB doesn't use arange):

$ mips-linux-gnu-readelf -wR foobar
Contents of the .debug_ranges section:

    Offset   Begin    End
    00000000 00400680 00400690
    00000000 00400490 004004a4
    00000000 <End of list>

$

-- no sign of the ISA bit anywhere -- line info:

$ mips-linux-gnu-readelf -wl foobar
Raw dump of debug contents of section .debug_line:
[...]
  Offset:                      0x27
  Length:                      78
  DWARF Version:               2
  Prologue Length:             31
  Minimum Instruction Length:  1
  Initial value of 'is_stmt':  1
  Line Base:                   -5
  Line Range:                  14
  Opcode Base:                 13

 Opcodes:
  Opcode 1 has 0 args
  Opcode 2 has 1 args
  Opcode 3 has 1 args
  Opcode 4 has 1 args
  Opcode 5 has 1 args
  Opcode 6 has 0 args
  Opcode 7 has 0 args
  Opcode 8 has 0 args
  Opcode 9 has 1 args
  Opcode 10 has 0 args
  Opcode 11 has 0 args
  Opcode 12 has 1 args

 The Directory Table is empty.

 The File Name Table:
  Entry Dir     Time    Size    Name
  1     0       0       0       foobar.c

 Line Number Statements:
  Extended opcode 2: set Address to 0x400681
  Special opcode 6: advance Address by 0 to 0x400681 and Line by 1 to 2
  Special opcode 7: advance Address by 0 to 0x400681 and Line by 2 to 4
  Special opcode 55: advance Address by 3 to 0x400684 and Line by 8 to 12
  Special opcode 7: advance Address by 0 to 0x400684 and Line by 2 to 14
  Advance Line by -7 to 7
  Special opcode 131: advance Address by 9 to 0x40068d and Line by 0 to 7
  Special opcode 7: advance Address by 0 to 0x40068d and Line by 2 to 9
  Advance PC by 3 to 0x400690
  Extended opcode 1: End of Sequence

  Extended opcode 2: set Address to 0x400491
  Advance Line by 21 to 22
  Copy
  Special opcode 6: advance Address by 0 to 0x400491 and Line by 1 to 23
  Special opcode 60: advance Address by 4 to 0x400495 and Line by -1 to 22
  Special opcode 34: advance Address by 2 to 0x400497 and Line by 1 to 23
  Special opcode 62: advance Address by 4 to 0x40049b and Line by 1 to 24
  Special opcode 32: advance Address by 2 to 0x40049d and Line by -1 to 23
  Special opcode 6: advance Address by 0 to 0x40049d and Line by 1 to 24
  Advance PC by 7 to 0x4004a4
  Extended opcode 1: End of Sequence
[...]

-- a-ha, the ISA bit is there!  However it's not always right for some
reason, I don't have a small test case to show it, but here's an excerpt
from MIPS16 libc, a prologue of a function:

00019630 <__libc_init_first>:
   19630:       e8a0            jrc     ra
   19632:       6500            nop

00019634 <_init>:
   19634:       f000 6a11       li      v0,17
   19638:       f7d8 0b08       la      v1,15e00 <_DYNAMIC+0x15c54>
   1963c:       f400 3240       sll     v0,16
   19640:       e269            addu    v0,v1
   19642:       659a            move    gp,v0
   19644:       64f6            save    48,ra,s0-s1
   19646:       671c            move    s0,gp
   19648:       d204            sw      v0,16(sp)
   1964a:       f352 984c       lw      v0,-27828(s0)
   1964e:       6724            move    s1,a0

and the corresponding DWARF-2 line info:

 Line Number Statements:
  Extended opcode 2: set Address to 0x19631
  Advance Line by 44 to 45
  Copy
  Special opcode 8: advance Address by 0 to 0x19631 and Line by 3 to 48
  Special opcode 66: advance Address by 4 to 0x19635 and Line by 5 to 53
  Advance PC by constant 17 to 0x19646
  Special opcode 25: advance Address by 1 to 0x19647 and Line by 6 to 59
  Advance Line by -6 to 53
  Special opcode 33: advance Address by 2 to 0x19649 and Line by 0 to 53
  Special opcode 39: advance Address by 2 to 0x1964b and Line by 6 to 59
  Advance Line by -6 to 53
  Special opcode 61: advance Address by 4 to 0x1964f and Line by 0 to 53

-- see that "Advance PC by constant 17" there?  It clears the ISA bit,
however code at 0x19646 is not standard MIPS code at all.  For some
reason the constant is always 17, I've never seen DW_LNS_const_add_pc
used with any other value -- is that a binutils bug or what?

3. Solution:

I think we should retain the value of the ISA bit in code references,
that is effectively treat them as cookies as they indeed are (although
trivially calculated) rather than raw memory byte addresses.

In a perfect world both the static symbol table and the respective
DWARF-2 records should be fixed to include the ISA bit in all the cases.
I think however that this is infeasible.

All the uses of `_bfd_mips_elf_symbol_processing' can not necessarily be
tracked down.  This function is used by `elf_slurp_symbol_table' that in
turn is used by `bfd_canonicalize_symtab' and
`bfd_canonicalize_dynamic_symtab', which are public interfaces.

Similarly DWARF-2 records are used outside GDB, one notable if a bit
questionable is the exception unwinder (libgcc/unwind-dw2.c) -- I have
identified at least bits in `execute_cfa_program' and
`uw_frame_state_for', both around the calls to `_Unwind_IsSignalFrame',
that would need an update as they effectively flip the ISA bit freely;
see also the comment about MASK_RETURN_ADDR in gcc/config/mips/mips.h.
But there may be more places.  Any change in how DWARF-2 records are
produced would require an update there and would cause compatibility
problems with libgcc.a binaries already distributed; given that this is
a static library a complex change involving function renames would
likely be required.

I propose therefore to accept the existing inconsistencies and deal with
them entirely within GDB.  I have figured out that the ISA bit lost in
various places can still be recovered as long as we have symbol
information -- that'll have the `st_other' attribute correctly set to
one of standard MIPS/MIPS16/microMIPS encoding.

Here's the resulting change.  It adds a couple of new `gdbarch' hooks,
one to update symbol information with the ISA bit lost in
`_bfd_mips_elf_symbol_processing', and two other ones to adjust DWARF-2
records as they're processed.  The ISA bit is set in each address
handled according to information retrieved from the symbol table for the
symbol spanning the address if any; limits are adjusted based on the
address they point to related to the respective base address.
Additionally minimal symbol information has to be adjusted accordingly
in its gdbarch hook.

With these changes in place some complications with ISA bit juggling in
the PC that never fully worked can be removed from the MIPS backend.
Conversely, the generic dynamic linker event special breakpoint symbol
handler has to be updated to call the minimal symbol gdbarch hook to
record that the symbol is a MIPS16 or microMIPS address if applicable or
the breakpoint will be set at the wrong address and either fail to work
or cause SIGTRAPs (this is because the symbol is handled early on and
bypasses regular symbol processing).

4. Results obtained

The change fixes the example above -- to repeat only the crucial steps:

(gdb) break main
Breakpoint 1 at 0x400491: file foobar.c, line 23.
(gdb) run
Starting program: .../foobar

Breakpoint 1, main () at foobar.c:23
23        return foop ();
(gdb) print foo
$1 = {int (void)} 0x400681 <foo>
(gdb) set foop = bar
(gdb) advance bar
bar () at foobar.c:9
9       }
(gdb) disassemble
Dump of assembler code for function bar:
=> 0x0040068d <+0>:     jr      ra
   0x0040068f <+2>:     li      v0,2
End of assembler dump.
(gdb) finish
Run till exit from #0  bar () at foobar.c:9
main () at foobar.c:24
24      }
Value returned is $2 = 2
(gdb) continue
Continuing.
[Inferior 1 (process 14128) exited with code 02]
(gdb)

-- excellent!

The change removes about 90 failures per MIPS16 multilib in mips-sde-elf
testing too, results for MIPS16 are now similar to that for standard
MIPS; microMIPS results are a bit worse because of host-I/O problems in
QEMU used instead of MIPSsim for microMIPS testing only:

                === gdb Summary ===

# of expected passes            14299
# of unexpected failures        187
# of expected failures          56
# of known failures             58
# of unresolved testcases       11
# of untested testcases         52
# of unsupported tests          174

MIPS16:

                === gdb Summary ===

# of expected passes            14298
# of unexpected failures        187
# of unexpected successes       2
# of expected failures          54
# of known failures             58
# of unresolved testcases       12
# of untested testcases         52
# of unsupported tests          174

microMIPS:

                === gdb Summary ===

# of expected passes            14149
# of unexpected failures        201
# of unexpected successes       2
# of expected failures          54
# of known failures             58
# of unresolved testcases       7
# of untested testcases         53
# of unsupported tests          175

2014-12-12  Maciej W. Rozycki  <macro@codesourcery.com>
            Maciej W. Rozycki  <macro@mips.com>
            Pedro Alves  <pedro@codesourcery.com>

	gdb/
	* gdbarch.sh (elf_make_msymbol_special): Change type to `F',
	remove `predefault' and `invalid_p' initializers.
	(make_symbol_special): New architecture method.
	(adjust_dwarf2_addr, adjust_dwarf2_line): Likewise.
	(objfile, symbol): New declarations.
	* arch-utils.h (default_elf_make_msymbol_special): Remove
	prototype.
	(default_make_symbol_special): New prototype.
	(default_adjust_dwarf2_addr): Likewise.
	(default_adjust_dwarf2_line): Likewise.
	* mips-tdep.h (mips_unmake_compact_addr): New prototype.
	* arch-utils.c (default_elf_make_msymbol_special): Remove
	function.
	(default_make_symbol_special): New function.
	(default_adjust_dwarf2_addr): Likewise.
	(default_adjust_dwarf2_line): Likewise.
	* dwarf2-frame.c (decode_frame_entry_1): Call
	`gdbarch_adjust_dwarf2_addr'.
	* dwarf2loc.c (dwarf2_find_location_expression): Likewise.
	* dwarf2read.c (create_addrmap_from_index): Likewise.
	(process_psymtab_comp_unit_reader): Likewise.
	(add_partial_symbol): Likewise.
	(add_partial_subprogram): Likewise.
	(process_full_comp_unit): Likewise.
	(read_file_scope): Likewise.
	(read_func_scope): Likewise.  Call `gdbarch_make_symbol_special'.
	(read_lexical_block_scope): Call `gdbarch_adjust_dwarf2_addr'.
	(read_call_site_scope): Likewise.
	(dwarf2_ranges_read): Likewise.
	(dwarf2_record_block_ranges): Likewise.
	(read_attribute_value): Likewise.
	(dwarf_decode_lines_1): Call `gdbarch_adjust_dwarf2_line'.
	(new_symbol_full): Call `gdbarch_adjust_dwarf2_addr'.
	* elfread.c (elf_symtab_read): Don't call
	`gdbarch_elf_make_msymbol_special' if unset.
	* mips-linux-tdep.c (micromips_linux_sigframe_validate): Strip
	the ISA bit from the PC.
	* mips-tdep.c (mips_unmake_compact_addr): New function.
	(mips_elf_make_msymbol_special): Set the ISA bit in the symbol's
	address appropriately.
	(mips_make_symbol_special): New function.
	(mips_pc_is_mips): Set the ISA bit before symbol lookup.
	(mips_pc_is_mips16): Likewise.
	(mips_pc_is_micromips): Likewise.
	(mips_pc_isa): Likewise.
	(mips_adjust_dwarf2_addr): New function.
	(mips_adjust_dwarf2_line): Likewise.
	(mips_read_pc, mips_unwind_pc): Keep the ISA bit.
	(mips_addr_bits_remove): Likewise.
	(mips_skip_trampoline_code): Likewise.
	(mips_write_pc): Don't set the ISA bit.
	(mips_eabi_push_dummy_call): Likewise.
	(mips_o64_push_dummy_call): Likewise.
	(mips_gdbarch_init): Install `mips_make_symbol_special',
	`mips_adjust_dwarf2_addr' and `mips_adjust_dwarf2_line' gdbarch
	handlers.
	* solib.c (gdb_bfd_lookup_symbol_from_symtab): Get
	target-specific symbol address adjustments.
	* gdbarch.h: Regenerate.
	* gdbarch.c: Regenerate.

2014-12-12  Maciej W. Rozycki  <macro@codesourcery.com>

	gdb/testsuite/
	* gdb.base/func-ptrs.c: New file.
	* gdb.base/func-ptrs.exp: New file.
2014-12-12 13:49:06 +00:00

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/* Handle shared libraries for GDB, the GNU Debugger.
Copyright (C) 1990-2014 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include <sys/types.h>
#include <fcntl.h>
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbcore.h"
#include "command.h"
#include "target.h"
#include "frame.h"
#include "gdb_regex.h"
#include "inferior.h"
#include "environ.h"
#include "language.h"
#include "gdbcmd.h"
#include "completer.h"
#include "filenames.h" /* for DOSish file names */
#include "exec.h"
#include "solist.h"
#include "observer.h"
#include "readline/readline.h"
#include "remote.h"
#include "solib.h"
#include "interps.h"
#include "filesystem.h"
#include "gdb_bfd.h"
#include "filestuff.h"
/* Architecture-specific operations. */
/* Per-architecture data key. */
static struct gdbarch_data *solib_data;
static void *
solib_init (struct obstack *obstack)
{
struct target_so_ops **ops;
ops = OBSTACK_ZALLOC (obstack, struct target_so_ops *);
*ops = current_target_so_ops;
return ops;
}
static const struct target_so_ops *
solib_ops (struct gdbarch *gdbarch)
{
const struct target_so_ops **ops = gdbarch_data (gdbarch, solib_data);
return *ops;
}
/* Set the solib operations for GDBARCH to NEW_OPS. */
void
set_solib_ops (struct gdbarch *gdbarch, const struct target_so_ops *new_ops)
{
const struct target_so_ops **ops = gdbarch_data (gdbarch, solib_data);
*ops = new_ops;
}
/* external data declarations */
/* FIXME: gdbarch needs to control this variable, or else every
configuration needs to call set_solib_ops. */
struct target_so_ops *current_target_so_ops;
/* List of known shared objects */
#define so_list_head current_program_space->so_list
/* Local function prototypes */
/* If non-empty, this is a search path for loading non-absolute shared library
symbol files. This takes precedence over the environment variables PATH
and LD_LIBRARY_PATH. */
static char *solib_search_path = NULL;
static void
show_solib_search_path (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("The search path for loading non-absolute "
"shared library symbol files is %s.\n"),
value);
}
/* Same as HAVE_DOS_BASED_FILE_SYSTEM, but useable as an rvalue. */
#if (HAVE_DOS_BASED_FILE_SYSTEM)
# define DOS_BASED_FILE_SYSTEM 1
#else
# define DOS_BASED_FILE_SYSTEM 0
#endif
/* Returns the full pathname of the shared library file, or NULL if
not found. (The pathname is malloc'ed; it needs to be freed by the
caller.) *FD is set to either -1 or an open file handle for the
library.
Global variable GDB_SYSROOT is used as a prefix directory
to search for shared libraries if they have an absolute path.
Global variable SOLIB_SEARCH_PATH is used as a prefix directory
(or set of directories, as in LD_LIBRARY_PATH) to search for all
shared libraries if not found in GDB_SYSROOT.
Search algorithm:
* If there is a gdb_sysroot and path is absolute:
* Search for gdb_sysroot/path.
* else
* Look for it literally (unmodified).
* Look in SOLIB_SEARCH_PATH.
* If available, use target defined search function.
* If gdb_sysroot is NOT set, perform the following two searches:
* Look in inferior's $PATH.
* Look in inferior's $LD_LIBRARY_PATH.
*
* The last check avoids doing this search when targetting remote
* machines since gdb_sysroot will almost always be set.
*/
char *
solib_find (char *in_pathname, int *fd)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
int found_file = -1;
char *temp_pathname = NULL;
int gdb_sysroot_is_empty;
const char *solib_symbols_extension
= gdbarch_solib_symbols_extension (target_gdbarch ());
const char *fskind = effective_target_file_system_kind ();
struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
char *sysroot = NULL;
/* If solib_symbols_extension is set, replace the file's
extension. */
if (solib_symbols_extension)
{
char *p = in_pathname + strlen (in_pathname);
while (p > in_pathname && *p != '.')
p--;
if (*p == '.')
{
char *new_pathname;
new_pathname = alloca (p - in_pathname + 1
+ strlen (solib_symbols_extension) + 1);
memcpy (new_pathname, in_pathname, p - in_pathname + 1);
strcpy (new_pathname + (p - in_pathname) + 1,
solib_symbols_extension);
in_pathname = new_pathname;
}
}
gdb_sysroot_is_empty = (gdb_sysroot == NULL || *gdb_sysroot == 0);
if (!gdb_sysroot_is_empty)
{
int prefix_len = strlen (gdb_sysroot);
/* Remove trailing slashes from absolute prefix. */
while (prefix_len > 0
&& IS_DIR_SEPARATOR (gdb_sysroot[prefix_len - 1]))
prefix_len--;
sysroot = savestring (gdb_sysroot, prefix_len);
make_cleanup (xfree, sysroot);
}
/* If we're on a non-DOS-based system, backslashes won't be
understood as directory separator, so, convert them to forward
slashes, iff we're supposed to handle DOS-based file system
semantics for target paths. */
if (!DOS_BASED_FILE_SYSTEM && fskind == file_system_kind_dos_based)
{
char *p;
/* Avoid clobbering our input. */
p = alloca (strlen (in_pathname) + 1);
strcpy (p, in_pathname);
in_pathname = p;
for (; *p; p++)
{
if (*p == '\\')
*p = '/';
}
}
/* Note, we're interested in IS_TARGET_ABSOLUTE_PATH, not
IS_ABSOLUTE_PATH. The latter is for host paths only, while
IN_PATHNAME is a target path. For example, if we're supposed to
be handling DOS-like semantics we want to consider a
'c:/foo/bar.dll' path as an absolute path, even on a Unix box.
With such a path, before giving up on the sysroot, we'll try:
1st attempt, c:/foo/bar.dll ==> /sysroot/c:/foo/bar.dll
2nd attempt, c:/foo/bar.dll ==> /sysroot/c/foo/bar.dll
3rd attempt, c:/foo/bar.dll ==> /sysroot/foo/bar.dll
*/
if (!IS_TARGET_ABSOLUTE_PATH (fskind, in_pathname) || gdb_sysroot_is_empty)
temp_pathname = xstrdup (in_pathname);
else
{
int need_dir_separator;
/* Concatenate the sysroot and the target reported filename. We
may need to glue them with a directory separator. Cases to
consider:
| sysroot | separator | in_pathname |
|-----------------+-----------+----------------|
| /some/dir | / | c:/foo/bar.dll |
| /some/dir | | /foo/bar.dll |
| remote: | | c:/foo/bar.dll |
| remote: | | /foo/bar.dll |
| remote:some/dir | / | c:/foo/bar.dll |
| remote:some/dir | | /foo/bar.dll |
IOW, we don't need to add a separator if IN_PATHNAME already
has one, or when the the sysroot is exactly "remote:".
There's no need to check for drive spec explicitly, as we only
get here if IN_PATHNAME is considered an absolute path. */
need_dir_separator = !(IS_DIR_SEPARATOR (in_pathname[0])
|| strcmp (REMOTE_SYSROOT_PREFIX, sysroot) == 0);
/* Cat the prefixed pathname together. */
temp_pathname = concat (sysroot,
need_dir_separator ? SLASH_STRING : "",
in_pathname, (char *) NULL);
}
/* Handle remote files. */
if (remote_filename_p (temp_pathname))
{
*fd = -1;
do_cleanups (old_chain);
return temp_pathname;
}
/* Now see if we can open it. */
found_file = gdb_open_cloexec (temp_pathname, O_RDONLY | O_BINARY, 0);
if (found_file < 0)
xfree (temp_pathname);
/* If the search in gdb_sysroot failed, and the path name has a
drive spec (e.g, c:/foo), try stripping ':' from the drive spec,
and retrying in the sysroot:
c:/foo/bar.dll ==> /sysroot/c/foo/bar.dll. */
if (found_file < 0
&& !gdb_sysroot_is_empty
&& HAS_TARGET_DRIVE_SPEC (fskind, in_pathname))
{
int need_dir_separator = !IS_DIR_SEPARATOR (in_pathname[2]);
char *drive = savestring (in_pathname, 1);
temp_pathname = concat (sysroot,
SLASH_STRING,
drive,
need_dir_separator ? SLASH_STRING : "",
in_pathname + 2, (char *) NULL);
xfree (drive);
found_file = gdb_open_cloexec (temp_pathname, O_RDONLY | O_BINARY, 0);
if (found_file < 0)
{
xfree (temp_pathname);
/* If the search in gdb_sysroot still failed, try fully
stripping the drive spec, and trying once more in the
sysroot before giving up.
c:/foo/bar.dll ==> /sysroot/foo/bar.dll. */
temp_pathname = concat (sysroot,
need_dir_separator ? SLASH_STRING : "",
in_pathname + 2, (char *) NULL);
found_file = gdb_open_cloexec (temp_pathname, O_RDONLY | O_BINARY, 0);
if (found_file < 0)
xfree (temp_pathname);
}
}
do_cleanups (old_chain);
/* We try to find the library in various ways. After each attempt,
either found_file >= 0 and temp_pathname is a malloc'd string, or
found_file < 0 and temp_pathname does not point to storage that
needs to be freed. */
if (found_file < 0)
temp_pathname = NULL;
/* If the search in gdb_sysroot failed, and the path name is
absolute at this point, make it relative. (openp will try and open the
file according to its absolute path otherwise, which is not what we want.)
Affects subsequent searches for this solib. */
if (found_file < 0 && IS_TARGET_ABSOLUTE_PATH (fskind, in_pathname))
{
/* First, get rid of any drive letters etc. */
while (!IS_TARGET_DIR_SEPARATOR (fskind, *in_pathname))
in_pathname++;
/* Next, get rid of all leading dir separators. */
while (IS_TARGET_DIR_SEPARATOR (fskind, *in_pathname))
in_pathname++;
}
/* If not found, search the solib_search_path (if any). */
if (found_file < 0 && solib_search_path != NULL)
found_file = openp (solib_search_path,
OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH,
in_pathname, O_RDONLY | O_BINARY, &temp_pathname);
/* If not found, next search the solib_search_path (if any) for the basename
only (ignoring the path). This is to allow reading solibs from a path
that differs from the opened path. */
if (found_file < 0 && solib_search_path != NULL)
found_file = openp (solib_search_path,
OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH,
target_lbasename (fskind, in_pathname),
O_RDONLY | O_BINARY, &temp_pathname);
/* If not found, try to use target supplied solib search method. */
if (found_file < 0 && ops->find_and_open_solib)
found_file = ops->find_and_open_solib (in_pathname, O_RDONLY | O_BINARY,
&temp_pathname);
/* If not found, next search the inferior's $PATH environment variable. */
if (found_file < 0 && gdb_sysroot_is_empty)
found_file = openp (get_in_environ (current_inferior ()->environment,
"PATH"),
OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH, in_pathname,
O_RDONLY | O_BINARY, &temp_pathname);
/* If not found, next search the inferior's $LD_LIBRARY_PATH
environment variable. */
if (found_file < 0 && gdb_sysroot_is_empty)
found_file = openp (get_in_environ (current_inferior ()->environment,
"LD_LIBRARY_PATH"),
OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH, in_pathname,
O_RDONLY | O_BINARY, &temp_pathname);
*fd = found_file;
return temp_pathname;
}
/* Open and return a BFD for the shared library PATHNAME. If FD is not -1,
it is used as file handle to open the file. Throws an error if the file
could not be opened. Handles both local and remote file access.
PATHNAME must be malloc'ed by the caller. It will be freed by this
function. If unsuccessful, the FD will be closed (unless FD was
-1). */
bfd *
solib_bfd_fopen (char *pathname, int fd)
{
bfd *abfd;
if (remote_filename_p (pathname))
{
gdb_assert (fd == -1);
abfd = remote_bfd_open (pathname, gnutarget);
}
else
{
abfd = gdb_bfd_open (pathname, gnutarget, fd);
if (abfd)
bfd_set_cacheable (abfd, 1);
}
if (!abfd)
{
make_cleanup (xfree, pathname);
error (_("Could not open `%s' as an executable file: %s"),
pathname, bfd_errmsg (bfd_get_error ()));
}
xfree (pathname);
return abfd;
}
/* Find shared library PATHNAME and open a BFD for it. */
bfd *
solib_bfd_open (char *pathname)
{
char *found_pathname;
int found_file;
bfd *abfd;
const struct bfd_arch_info *b;
/* Search for shared library file. */
found_pathname = solib_find (pathname, &found_file);
if (found_pathname == NULL)
{
/* Return failure if the file could not be found, so that we can
accumulate messages about missing libraries. */
if (errno == ENOENT)
return NULL;
perror_with_name (pathname);
}
/* Open bfd for shared library. */
abfd = solib_bfd_fopen (found_pathname, found_file);
/* Check bfd format. */
if (!bfd_check_format (abfd, bfd_object))
{
make_cleanup_bfd_unref (abfd);
error (_("`%s': not in executable format: %s"),
bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
}
/* Check bfd arch. */
b = gdbarch_bfd_arch_info (target_gdbarch ());
if (!b->compatible (b, bfd_get_arch_info (abfd)))
warning (_("`%s': Shared library architecture %s is not compatible "
"with target architecture %s."), bfd_get_filename (abfd),
bfd_get_arch_info (abfd)->printable_name, b->printable_name);
return abfd;
}
/* Given a pointer to one of the shared objects in our list of mapped
objects, use the recorded name to open a bfd descriptor for the
object, build a section table, relocate all the section addresses
by the base address at which the shared object was mapped, and then
add the sections to the target's section table.
FIXME: In most (all?) cases the shared object file name recorded in
the dynamic linkage tables will be a fully qualified pathname. For
cases where it isn't, do we really mimic the systems search
mechanism correctly in the below code (particularly the tilde
expansion stuff?). */
static int
solib_map_sections (struct so_list *so)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
char *filename;
struct target_section *p;
struct cleanup *old_chain;
bfd *abfd;
filename = tilde_expand (so->so_name);
old_chain = make_cleanup (xfree, filename);
abfd = ops->bfd_open (filename);
do_cleanups (old_chain);
if (abfd == NULL)
return 0;
/* Leave bfd open, core_xfer_memory and "info files" need it. */
so->abfd = abfd;
/* Copy the full path name into so_name, allowing symbol_file_add
to find it later. This also affects the =library-loaded GDB/MI
event, and in particular the part of that notification providing
the library's host-side path. If we let the target dictate
that objfile's path, and the target is different from the host,
GDB/MI will not provide the correct host-side path. */
if (strlen (bfd_get_filename (abfd)) >= SO_NAME_MAX_PATH_SIZE)
error (_("Shared library file name is too long."));
strcpy (so->so_name, bfd_get_filename (abfd));
if (build_section_table (abfd, &so->sections, &so->sections_end))
{
error (_("Can't find the file sections in `%s': %s"),
bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
}
for (p = so->sections; p < so->sections_end; p++)
{
/* Relocate the section binding addresses as recorded in the shared
object's file by the base address to which the object was actually
mapped. */
ops->relocate_section_addresses (so, p);
/* If the target didn't provide information about the address
range of the shared object, assume we want the location of
the .text section. */
if (so->addr_low == 0 && so->addr_high == 0
&& strcmp (p->the_bfd_section->name, ".text") == 0)
{
so->addr_low = p->addr;
so->addr_high = p->endaddr;
}
}
/* Add the shared object's sections to the current set of file
section tables. Do this immediately after mapping the object so
that later nodes in the list can query this object, as is needed
in solib-osf.c. */
add_target_sections (so, so->sections, so->sections_end);
return 1;
}
/* Free symbol-file related contents of SO and reset for possible reloading
of SO. If we have opened a BFD for SO, close it. If we have placed SO's
sections in some target's section table, the caller is responsible for
removing them.
This function doesn't mess with objfiles at all. If there is an
objfile associated with SO that needs to be removed, the caller is
responsible for taking care of that. */
static void
clear_so (struct so_list *so)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
if (so->sections)
{
xfree (so->sections);
so->sections = so->sections_end = NULL;
}
gdb_bfd_unref (so->abfd);
so->abfd = NULL;
/* Our caller closed the objfile, possibly via objfile_purge_solibs. */
so->symbols_loaded = 0;
so->objfile = NULL;
so->addr_low = so->addr_high = 0;
/* Restore the target-supplied file name. SO_NAME may be the path
of the symbol file. */
strcpy (so->so_name, so->so_original_name);
/* Do the same for target-specific data. */
if (ops->clear_so != NULL)
ops->clear_so (so);
}
/* Free the storage associated with the `struct so_list' object SO.
If we have opened a BFD for SO, close it.
The caller is responsible for removing SO from whatever list it is
a member of. If we have placed SO's sections in some target's
section table, the caller is responsible for removing them.
This function doesn't mess with objfiles at all. If there is an
objfile associated with SO that needs to be removed, the caller is
responsible for taking care of that. */
void
free_so (struct so_list *so)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
clear_so (so);
ops->free_so (so);
xfree (so);
}
/* Return address of first so_list entry in master shared object list. */
struct so_list *
master_so_list (void)
{
return so_list_head;
}
/* Read in symbols for shared object SO. If SYMFILE_VERBOSE is set in FLAGS,
be chatty about it. Return non-zero if any symbols were actually
loaded. */
int
solib_read_symbols (struct so_list *so, int flags)
{
if (so->symbols_loaded)
{
/* If needed, we've already warned in our caller. */
}
else if (so->abfd == NULL)
{
/* We've already warned about this library, when trying to open
it. */
}
else
{
volatile struct gdb_exception e;
flags |= current_inferior ()->symfile_flags;
TRY_CATCH (e, RETURN_MASK_ERROR)
{
struct section_addr_info *sap;
/* Have we already loaded this shared object? */
ALL_OBJFILES (so->objfile)
{
if (filename_cmp (objfile_name (so->objfile), so->so_name) == 0
&& so->objfile->addr_low == so->addr_low)
break;
}
if (so->objfile != NULL)
break;
sap = build_section_addr_info_from_section_table (so->sections,
so->sections_end);
so->objfile = symbol_file_add_from_bfd (so->abfd, so->so_name,
flags, sap, OBJF_SHARED,
NULL);
so->objfile->addr_low = so->addr_low;
free_section_addr_info (sap);
}
if (e.reason < 0)
exception_fprintf (gdb_stderr, e, _("Error while reading shared"
" library symbols for %s:\n"),
so->so_name);
else
so->symbols_loaded = 1;
return 1;
}
return 0;
}
/* Return 1 if KNOWN->objfile is used by any other so_list object in the
SO_LIST_HEAD list. Return 0 otherwise. */
static int
solib_used (const struct so_list *const known)
{
const struct so_list *pivot;
for (pivot = so_list_head; pivot != NULL; pivot = pivot->next)
if (pivot != known && pivot->objfile == known->objfile)
return 1;
return 0;
}
/* Synchronize GDB's shared object list with inferior's.
Extract the list of currently loaded shared objects from the
inferior, and compare it with the list of shared objects currently
in GDB's so_list_head list. Edit so_list_head to bring it in sync
with the inferior's new list.
If we notice that the inferior has unloaded some shared objects,
free any symbolic info GDB had read about those shared objects.
Don't load symbolic info for any new shared objects; just add them
to the list, and leave their symbols_loaded flag clear.
If FROM_TTY is non-null, feel free to print messages about what
we're doing.
If TARGET is non-null, add the sections of all new shared objects
to TARGET's section table. Note that this doesn't remove any
sections for shared objects that have been unloaded, and it
doesn't check to see if the new shared objects are already present in
the section table. But we only use this for core files and
processes we've just attached to, so that's okay. */
static void
update_solib_list (int from_tty, struct target_ops *target)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
struct so_list *inferior = ops->current_sos();
struct so_list *gdb, **gdb_link;
/* We can reach here due to changing solib-search-path or the
sysroot, before having any inferior. */
if (target_has_execution && !ptid_equal (inferior_ptid, null_ptid))
{
struct inferior *inf = current_inferior ();
/* If we are attaching to a running process for which we
have not opened a symbol file, we may be able to get its
symbols now! */
if (inf->attach_flag && symfile_objfile == NULL)
catch_errors (ops->open_symbol_file_object, &from_tty,
"Error reading attached process's symbol file.\n",
RETURN_MASK_ALL);
}
/* GDB and the inferior's dynamic linker each maintain their own
list of currently loaded shared objects; we want to bring the
former in sync with the latter. Scan both lists, seeing which
shared objects appear where. There are three cases:
- A shared object appears on both lists. This means that GDB
knows about it already, and it's still loaded in the inferior.
Nothing needs to happen.
- A shared object appears only on GDB's list. This means that
the inferior has unloaded it. We should remove the shared
object from GDB's tables.
- A shared object appears only on the inferior's list. This
means that it's just been loaded. We should add it to GDB's
tables.
So we walk GDB's list, checking each entry to see if it appears
in the inferior's list too. If it does, no action is needed, and
we remove it from the inferior's list. If it doesn't, the
inferior has unloaded it, and we remove it from GDB's list. By
the time we're done walking GDB's list, the inferior's list
contains only the new shared objects, which we then add. */
gdb = so_list_head;
gdb_link = &so_list_head;
while (gdb)
{
struct so_list *i = inferior;
struct so_list **i_link = &inferior;
/* Check to see whether the shared object *gdb also appears in
the inferior's current list. */
while (i)
{
if (ops->same)
{
if (ops->same (gdb, i))
break;
}
else
{
if (! filename_cmp (gdb->so_original_name, i->so_original_name))
break;
}
i_link = &i->next;
i = *i_link;
}
/* If the shared object appears on the inferior's list too, then
it's still loaded, so we don't need to do anything. Delete
it from the inferior's list, and leave it on GDB's list. */
if (i)
{
*i_link = i->next;
free_so (i);
gdb_link = &gdb->next;
gdb = *gdb_link;
}
/* If it's not on the inferior's list, remove it from GDB's tables. */
else
{
/* Notify any observer that the shared object has been
unloaded before we remove it from GDB's tables. */
observer_notify_solib_unloaded (gdb);
VEC_safe_push (char_ptr, current_program_space->deleted_solibs,
xstrdup (gdb->so_name));
*gdb_link = gdb->next;
/* Unless the user loaded it explicitly, free SO's objfile. */
if (gdb->objfile && ! (gdb->objfile->flags & OBJF_USERLOADED)
&& !solib_used (gdb))
free_objfile (gdb->objfile);
/* Some targets' section tables might be referring to
sections from so->abfd; remove them. */
remove_target_sections (gdb);
free_so (gdb);
gdb = *gdb_link;
}
}
/* Now the inferior's list contains only shared objects that don't
appear in GDB's list --- those that are newly loaded. Add them
to GDB's shared object list. */
if (inferior)
{
int not_found = 0;
const char *not_found_filename = NULL;
struct so_list *i;
/* Add the new shared objects to GDB's list. */
*gdb_link = inferior;
/* Fill in the rest of each of the `struct so_list' nodes. */
for (i = inferior; i; i = i->next)
{
volatile struct gdb_exception e;
i->pspace = current_program_space;
VEC_safe_push (so_list_ptr, current_program_space->added_solibs, i);
TRY_CATCH (e, RETURN_MASK_ERROR)
{
/* Fill in the rest of the `struct so_list' node. */
if (!solib_map_sections (i))
{
not_found++;
if (not_found_filename == NULL)
not_found_filename = i->so_original_name;
}
}
if (e.reason < 0)
exception_fprintf (gdb_stderr, e,
_("Error while mapping shared "
"library sections:\n"));
/* Notify any observer that the shared object has been
loaded now that we've added it to GDB's tables. */
observer_notify_solib_loaded (i);
}
/* If a library was not found, issue an appropriate warning
message. We have to use a single call to warning in case the
front end does something special with warnings, e.g., pop up
a dialog box. It Would Be Nice if we could get a "warning: "
prefix on each line in the CLI front end, though - it doesn't
stand out well. */
if (not_found == 1)
warning (_("Could not load shared library symbols for %s.\n"
"Do you need \"set solib-search-path\" "
"or \"set sysroot\"?"),
not_found_filename);
else if (not_found > 1)
warning (_("\
Could not load shared library symbols for %d libraries, e.g. %s.\n\
Use the \"info sharedlibrary\" command to see the complete listing.\n\
Do you need \"set solib-search-path\" or \"set sysroot\"?"),
not_found, not_found_filename);
}
}
/* Return non-zero if NAME is the libpthread shared library.
Uses a fairly simplistic heuristic approach where we check
the file name against "/libpthread". This can lead to false
positives, but this should be good enough in practice. */
int
libpthread_name_p (const char *name)
{
return (strstr (name, "/libpthread") != NULL);
}
/* Return non-zero if SO is the libpthread shared library. */
static int
libpthread_solib_p (struct so_list *so)
{
return libpthread_name_p (so->so_name);
}
/* Read in symbolic information for any shared objects whose names
match PATTERN. (If we've already read a shared object's symbol
info, leave it alone.) If PATTERN is zero, read them all.
If READSYMS is 0, defer reading symbolic information until later
but still do any needed low level processing.
FROM_TTY and TARGET are as described for update_solib_list, above. */
void
solib_add (const char *pattern, int from_tty,
struct target_ops *target, int readsyms)
{
struct so_list *gdb;
if (print_symbol_loading_p (from_tty, 0, 0))
{
if (pattern != NULL)
{
printf_unfiltered (_("Loading symbols for shared libraries: %s\n"),
pattern);
}
else
printf_unfiltered (_("Loading symbols for shared libraries.\n"));
}
current_program_space->solib_add_generation++;
if (pattern)
{
char *re_err = re_comp (pattern);
if (re_err)
error (_("Invalid regexp: %s"), re_err);
}
update_solib_list (from_tty, target);
/* Walk the list of currently loaded shared libraries, and read
symbols for any that match the pattern --- or any whose symbols
aren't already loaded, if no pattern was given. */
{
int any_matches = 0;
int loaded_any_symbols = 0;
const int flags =
SYMFILE_DEFER_BP_RESET | (from_tty ? SYMFILE_VERBOSE : 0);
for (gdb = so_list_head; gdb; gdb = gdb->next)
if (! pattern || re_exec (gdb->so_name))
{
/* Normally, we would read the symbols from that library
only if READSYMS is set. However, we're making a small
exception for the pthread library, because we sometimes
need the library symbols to be loaded in order to provide
thread support (x86-linux for instance). */
const int add_this_solib =
(readsyms || libpthread_solib_p (gdb));
any_matches = 1;
if (add_this_solib)
{
if (gdb->symbols_loaded)
{
/* If no pattern was given, be quiet for shared
libraries we have already loaded. */
if (pattern && (from_tty || info_verbose))
printf_unfiltered (_("Symbols already loaded for %s\n"),
gdb->so_name);
}
else if (solib_read_symbols (gdb, flags))
loaded_any_symbols = 1;
}
}
if (loaded_any_symbols)
breakpoint_re_set ();
if (from_tty && pattern && ! any_matches)
printf_unfiltered
("No loaded shared libraries match the pattern `%s'.\n", pattern);
if (loaded_any_symbols)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
/* Getting new symbols may change our opinion about what is
frameless. */
reinit_frame_cache ();
ops->special_symbol_handling ();
}
}
}
/* Implement the "info sharedlibrary" command. Walk through the
shared library list and print information about each attached
library matching PATTERN. If PATTERN is elided, print them
all. */
static void
info_sharedlibrary_command (char *pattern, int from_tty)
{
struct so_list *so = NULL; /* link map state variable */
int so_missing_debug_info = 0;
int addr_width;
int nr_libs;
struct cleanup *table_cleanup;
struct gdbarch *gdbarch = target_gdbarch ();
struct ui_out *uiout = current_uiout;
if (pattern)
{
char *re_err = re_comp (pattern);
if (re_err)
error (_("Invalid regexp: %s"), re_err);
}
/* "0x", a little whitespace, and two hex digits per byte of pointers. */
addr_width = 4 + (gdbarch_ptr_bit (gdbarch) / 4);
update_solib_list (from_tty, 0);
/* make_cleanup_ui_out_table_begin_end needs to know the number of
rows, so we need to make two passes over the libs. */
for (nr_libs = 0, so = so_list_head; so; so = so->next)
{
if (so->so_name[0])
{
if (pattern && ! re_exec (so->so_name))
continue;
++nr_libs;
}
}
table_cleanup =
make_cleanup_ui_out_table_begin_end (uiout, 4, nr_libs,
"SharedLibraryTable");
/* The "- 1" is because ui_out adds one space between columns. */
ui_out_table_header (uiout, addr_width - 1, ui_left, "from", "From");
ui_out_table_header (uiout, addr_width - 1, ui_left, "to", "To");
ui_out_table_header (uiout, 12 - 1, ui_left, "syms-read", "Syms Read");
ui_out_table_header (uiout, 0, ui_noalign,
"name", "Shared Object Library");
ui_out_table_body (uiout);
for (so = so_list_head; so; so = so->next)
{
struct cleanup *lib_cleanup;
if (! so->so_name[0])
continue;
if (pattern && ! re_exec (so->so_name))
continue;
lib_cleanup = make_cleanup_ui_out_tuple_begin_end (uiout, "lib");
if (so->addr_high != 0)
{
ui_out_field_core_addr (uiout, "from", gdbarch, so->addr_low);
ui_out_field_core_addr (uiout, "to", gdbarch, so->addr_high);
}
else
{
ui_out_field_skip (uiout, "from");
ui_out_field_skip (uiout, "to");
}
if (! ui_out_is_mi_like_p (interp_ui_out (top_level_interpreter ()))
&& so->symbols_loaded
&& !objfile_has_symbols (so->objfile))
{
so_missing_debug_info = 1;
ui_out_field_string (uiout, "syms-read", "Yes (*)");
}
else
ui_out_field_string (uiout, "syms-read",
so->symbols_loaded ? "Yes" : "No");
ui_out_field_string (uiout, "name", so->so_name);
ui_out_text (uiout, "\n");
do_cleanups (lib_cleanup);
}
do_cleanups (table_cleanup);
if (nr_libs == 0)
{
if (pattern)
ui_out_message (uiout, 0,
_("No shared libraries matched.\n"));
else
ui_out_message (uiout, 0,
_("No shared libraries loaded at this time.\n"));
}
else
{
if (so_missing_debug_info)
ui_out_message (uiout, 0,
_("(*): Shared library is missing "
"debugging information.\n"));
}
}
/* Return 1 if ADDRESS lies within SOLIB. */
int
solib_contains_address_p (const struct so_list *const solib,
CORE_ADDR address)
{
struct target_section *p;
for (p = solib->sections; p < solib->sections_end; p++)
if (p->addr <= address && address < p->endaddr)
return 1;
return 0;
}
/* If ADDRESS is in a shared lib in program space PSPACE, return its
name.
Provides a hook for other gdb routines to discover whether or not a
particular address is within the mapped address space of a shared
library.
For example, this routine is called at one point to disable
breakpoints which are in shared libraries that are not currently
mapped in. */
char *
solib_name_from_address (struct program_space *pspace, CORE_ADDR address)
{
struct so_list *so = NULL;
for (so = pspace->so_list; so; so = so->next)
if (solib_contains_address_p (so, address))
return (so->so_name);
return (0);
}
/* Return whether the data starting at VADDR, size SIZE, must be kept
in a core file for shared libraries loaded before "gcore" is used
to be handled correctly when the core file is loaded. This only
applies when the section would otherwise not be kept in the core
file (in particular, for readonly sections). */
int
solib_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
if (ops->keep_data_in_core)
return ops->keep_data_in_core (vaddr, size);
else
return 0;
}
/* Called by free_all_symtabs */
void
clear_solib (void)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
/* This function is expected to handle ELF shared libraries. It is
also used on Solaris, which can run either ELF or a.out binaries
(for compatibility with SunOS 4), both of which can use shared
libraries. So we don't know whether we have an ELF executable or
an a.out executable until the user chooses an executable file.
ELF shared libraries don't get mapped into the address space
until after the program starts, so we'd better not try to insert
breakpoints in them immediately. We have to wait until the
dynamic linker has loaded them; we'll hit a bp_shlib_event
breakpoint (look for calls to create_solib_event_breakpoint) when
it's ready.
SunOS shared libraries seem to be different --- they're present
as soon as the process begins execution, so there's no need to
put off inserting breakpoints. There's also nowhere to put a
bp_shlib_event breakpoint, so if we put it off, we'll never get
around to it.
So: disable breakpoints only if we're using ELF shared libs. */
if (exec_bfd != NULL
&& bfd_get_flavour (exec_bfd) != bfd_target_aout_flavour)
disable_breakpoints_in_shlibs ();
while (so_list_head)
{
struct so_list *so = so_list_head;
so_list_head = so->next;
observer_notify_solib_unloaded (so);
remove_target_sections (so);
free_so (so);
}
ops->clear_solib ();
}
/* Shared library startup support. When GDB starts up the inferior,
it nurses it along (through the shell) until it is ready to execute
its first instruction. At this point, this function gets
called. */
void
solib_create_inferior_hook (int from_tty)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
ops->solib_create_inferior_hook (from_tty);
}
/* Check to see if an address is in the dynamic loader's dynamic
symbol resolution code. Return 1 if so, 0 otherwise. */
int
in_solib_dynsym_resolve_code (CORE_ADDR pc)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
return ops->in_dynsym_resolve_code (pc);
}
/* Implements the "sharedlibrary" command. */
static void
sharedlibrary_command (char *args, int from_tty)
{
dont_repeat ();
solib_add (args, from_tty, (struct target_ops *) 0, 1);
}
/* Implements the command "nosharedlibrary", which discards symbols
that have been auto-loaded from shared libraries. Symbols from
shared libraries that were added by explicit request of the user
are not discarded. Also called from remote.c. */
void
no_shared_libraries (char *ignored, int from_tty)
{
/* The order of the two routines below is important: clear_solib notifies
the solib_unloaded observers, and some of these observers might need
access to their associated objfiles. Therefore, we can not purge the
solibs' objfiles before clear_solib has been called. */
clear_solib ();
objfile_purge_solibs ();
}
/* See solib.h. */
void
update_solib_breakpoints (void)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
if (ops->update_breakpoints != NULL)
ops->update_breakpoints ();
}
/* See solib.h. */
void
handle_solib_event (void)
{
const struct target_so_ops *ops = solib_ops (target_gdbarch ());
if (ops->handle_event != NULL)
ops->handle_event ();
clear_program_space_solib_cache (current_inferior ()->pspace);
/* Check for any newly added shared libraries if we're supposed to
be adding them automatically. Switch terminal for any messages
produced by breakpoint_re_set. */
target_terminal_ours_for_output ();
solib_add (NULL, 0, &current_target, auto_solib_add);
target_terminal_inferior ();
}
/* Reload shared libraries, but avoid reloading the same symbol file
we already have loaded. */
static void
reload_shared_libraries_1 (int from_tty)
{
struct so_list *so;
struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
if (print_symbol_loading_p (from_tty, 0, 0))
printf_unfiltered (_("Loading symbols for shared libraries.\n"));
for (so = so_list_head; so != NULL; so = so->next)
{
char *filename, *found_pathname = NULL;
bfd *abfd;
int was_loaded = so->symbols_loaded;
const int flags =
SYMFILE_DEFER_BP_RESET | (from_tty ? SYMFILE_VERBOSE : 0);
filename = tilde_expand (so->so_original_name);
make_cleanup (xfree, filename);
abfd = solib_bfd_open (filename);
if (abfd != NULL)
{
found_pathname = xstrdup (bfd_get_filename (abfd));
make_cleanup (xfree, found_pathname);
gdb_bfd_unref (abfd);
}
/* If this shared library is no longer associated with its previous
symbol file, close that. */
if ((found_pathname == NULL && was_loaded)
|| (found_pathname != NULL
&& filename_cmp (found_pathname, so->so_name) != 0))
{
if (so->objfile && ! (so->objfile->flags & OBJF_USERLOADED)
&& !solib_used (so))
free_objfile (so->objfile);
remove_target_sections (so);
clear_so (so);
}
/* If this shared library is now associated with a new symbol
file, open it. */
if (found_pathname != NULL
&& (!was_loaded
|| filename_cmp (found_pathname, so->so_name) != 0))
{
volatile struct gdb_exception e;
TRY_CATCH (e, RETURN_MASK_ERROR)
solib_map_sections (so);
if (e.reason < 0)
exception_fprintf (gdb_stderr, e,
_("Error while mapping "
"shared library sections:\n"));
else if (auto_solib_add || was_loaded || libpthread_solib_p (so))
solib_read_symbols (so, flags);
}
}
do_cleanups (old_chain);
}
static void
reload_shared_libraries (char *ignored, int from_tty,
struct cmd_list_element *e)
{
const struct target_so_ops *ops;
reload_shared_libraries_1 (from_tty);
ops = solib_ops (target_gdbarch ());
/* Creating inferior hooks here has two purposes. First, if we reload
shared libraries then the address of solib breakpoint we've computed
previously might be no longer valid. For example, if we forgot to set
solib-absolute-prefix and are setting it right now, then the previous
breakpoint address is plain wrong. Second, installing solib hooks
also implicitly figures were ld.so is and loads symbols for it.
Absent this call, if we've just connected to a target and set
solib-absolute-prefix or solib-search-path, we'll lose all information
about ld.so. */
if (target_has_execution)
{
/* Reset or free private data structures not associated with
so_list entries. */
ops->clear_solib ();
/* Remove any previous solib event breakpoint. This is usually
done in common code, at breakpoint_init_inferior time, but
we're not really starting up the inferior here. */
remove_solib_event_breakpoints ();
solib_create_inferior_hook (from_tty);
}
/* Sometimes the platform-specific hook loads initial shared
libraries, and sometimes it doesn't. If it doesn't FROM_TTY will be
incorrectly 0 but such solib targets should be fixed anyway. If we
made all the inferior hook methods consistent, this call could be
removed. Call it only after the solib target has been initialized by
solib_create_inferior_hook. */
solib_add (NULL, 0, NULL, auto_solib_add);
breakpoint_re_set ();
/* We may have loaded or unloaded debug info for some (or all)
shared libraries. However, frames may still reference them. For
example, a frame's unwinder might still point at DWARF FDE
structures that are now freed. Also, getting new symbols may
change our opinion about what is frameless. */
reinit_frame_cache ();
ops->special_symbol_handling ();
}
static void
show_auto_solib_add (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Autoloading of shared library symbols is %s.\n"),
value);
}
/* Handler for library-specific lookup of global symbol NAME in OBJFILE. Call
the library-specific handler if it is installed for the current target. */
struct symbol *
solib_global_lookup (struct objfile *objfile,
const char *name,
const domain_enum domain)
{
const struct target_so_ops *ops = solib_ops (get_objfile_arch (objfile));
if (ops->lookup_lib_global_symbol != NULL)
return ops->lookup_lib_global_symbol (objfile, name, domain);
return NULL;
}
/* Lookup the value for a specific symbol from dynamic symbol table. Look
up symbol from ABFD. MATCH_SYM is a callback function to determine
whether to pick up a symbol. DATA is the input of this callback
function. Return NULL if symbol is not found. */
CORE_ADDR
gdb_bfd_lookup_symbol_from_symtab (bfd *abfd,
int (*match_sym) (asymbol *, void *),
void *data)
{
long storage_needed = bfd_get_symtab_upper_bound (abfd);
CORE_ADDR symaddr = 0;
if (storage_needed > 0)
{
unsigned int i;
asymbol **symbol_table = (asymbol **) xmalloc (storage_needed);
struct cleanup *back_to = make_cleanup (xfree, symbol_table);
unsigned int number_of_symbols =
bfd_canonicalize_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
asymbol *sym = *symbol_table++;
if (match_sym (sym, data))
{
struct gdbarch *gdbarch = target_gdbarch ();
symaddr = sym->value;
/* Some ELF targets fiddle with addresses of symbols they
consider special. They use minimal symbols to do that
and this is needed for correct breakpoint placement,
but we do not have full data here to build a complete
minimal symbol, so just set the address and let the
targets cope with that. */
if (bfd_get_flavour (abfd) == bfd_target_elf_flavour
&& gdbarch_elf_make_msymbol_special_p (gdbarch))
{
struct minimal_symbol msym;
memset (&msym, 0, sizeof (msym));
SET_MSYMBOL_VALUE_ADDRESS (&msym, symaddr);
gdbarch_elf_make_msymbol_special (gdbarch, sym, &msym);
symaddr = MSYMBOL_VALUE_RAW_ADDRESS (&msym);
}
/* BFD symbols are section relative. */
symaddr += sym->section->vma;
break;
}
}
do_cleanups (back_to);
}
return symaddr;
}
/* Lookup the value for a specific symbol from symbol table. Look up symbol
from ABFD. MATCH_SYM is a callback function to determine whether to pick
up a symbol. DATA is the input of this callback function. Return NULL
if symbol is not found. */
static CORE_ADDR
bfd_lookup_symbol_from_dyn_symtab (bfd *abfd,
int (*match_sym) (asymbol *, void *),
void *data)
{
long storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
CORE_ADDR symaddr = 0;
if (storage_needed > 0)
{
unsigned int i;
asymbol **symbol_table = (asymbol **) xmalloc (storage_needed);
struct cleanup *back_to = make_cleanup (xfree, symbol_table);
unsigned int number_of_symbols =
bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
asymbol *sym = *symbol_table++;
if (match_sym (sym, data))
{
/* BFD symbols are section relative. */
symaddr = sym->value + sym->section->vma;
break;
}
}
do_cleanups (back_to);
}
return symaddr;
}
/* Lookup the value for a specific symbol from symbol table and dynamic
symbol table. Look up symbol from ABFD. MATCH_SYM is a callback
function to determine whether to pick up a symbol. DATA is the
input of this callback function. Return NULL if symbol is not
found. */
CORE_ADDR
gdb_bfd_lookup_symbol (bfd *abfd,
int (*match_sym) (asymbol *, void *),
void *data)
{
CORE_ADDR symaddr = gdb_bfd_lookup_symbol_from_symtab (abfd, match_sym, data);
/* On FreeBSD, the dynamic linker is stripped by default. So we'll
have to check the dynamic string table too. */
if (symaddr == 0)
symaddr = bfd_lookup_symbol_from_dyn_symtab (abfd, match_sym, data);
return symaddr;
}
/* SO_LIST_HEAD may contain user-loaded object files that can be removed
out-of-band by the user. So upon notification of free_objfile remove
all references to any user-loaded file that is about to be freed. */
static void
remove_user_added_objfile (struct objfile *objfile)
{
struct so_list *so;
if (objfile != 0 && objfile->flags & OBJF_USERLOADED)
{
for (so = so_list_head; so != NULL; so = so->next)
if (so->objfile == objfile)
so->objfile = NULL;
}
}
extern initialize_file_ftype _initialize_solib; /* -Wmissing-prototypes */
void
_initialize_solib (void)
{
solib_data = gdbarch_data_register_pre_init (solib_init);
observer_attach_free_objfile (remove_user_added_objfile);
add_com ("sharedlibrary", class_files, sharedlibrary_command,
_("Load shared object library symbols for files matching REGEXP."));
add_info ("sharedlibrary", info_sharedlibrary_command,
_("Status of loaded shared object libraries."));
add_com ("nosharedlibrary", class_files, no_shared_libraries,
_("Unload all shared object library symbols."));
add_setshow_boolean_cmd ("auto-solib-add", class_support,
&auto_solib_add, _("\
Set autoloading of shared library symbols."), _("\
Show autoloading of shared library symbols."), _("\
If \"on\", symbols from all shared object libraries will be loaded\n\
automatically when the inferior begins execution, when the dynamic linker\n\
informs gdb that a new library has been loaded, or when attaching to the\n\
inferior. Otherwise, symbols must be loaded manually, using \
`sharedlibrary'."),
NULL,
show_auto_solib_add,
&setlist, &showlist);
add_setshow_filename_cmd ("sysroot", class_support,
&gdb_sysroot, _("\
Set an alternate system root."), _("\
Show the current system root."), _("\
The system root is used to load absolute shared library symbol files.\n\
For other (relative) files, you can add directories using\n\
`set solib-search-path'."),
reload_shared_libraries,
NULL,
&setlist, &showlist);
add_alias_cmd ("solib-absolute-prefix", "sysroot", class_support, 0,
&setlist);
add_alias_cmd ("solib-absolute-prefix", "sysroot", class_support, 0,
&showlist);
add_setshow_optional_filename_cmd ("solib-search-path", class_support,
&solib_search_path, _("\
Set the search path for loading non-absolute shared library symbol files."),
_("\
Show the search path for loading non-absolute shared library symbol files."),
_("\
This takes precedence over the environment variables \
PATH and LD_LIBRARY_PATH."),
reload_shared_libraries,
show_solib_search_path,
&setlist, &showlist);
}
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