This change addresses a regression in gdb.dwarf2/dw2-skip-prologue.exp
across MIPS16 multilibs:
(gdb) file .../gdb.dwarf2/dw2-skip-prologue
Reading symbols from .../gdb.d/gdb.dwarf2/dw2-skip-prologue...done.
(gdb) delete breakpoints
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) break main
warning: Breakpoint address adjusted from 0x00400725 to 0x00400721.
Breakpoint 1 at 0x400721
(gdb) set remotetimeout 5
(gdb) kill
The program is not being run.
(gdb)
[...]
target remote ...:2345
Reading symbols from .../mips16/lib/ld.so.1...done.
warning: Breakpoint address adjusted from 0x00400725 to 0x00400721.
warning: Breakpoint address adjusted from 0x00400725 to 0x00400721.
0x2aaa8e81 in __start () from .../mips16/lib/ld.so.1
(gdb) continue
Continuing.
warning: Breakpoint address adjusted from 0x00400725 to 0x00400721.
warning: Breakpoint 1 address previously adjusted from 0x00400725 to
0x00400721.
Breakpoint 1, 0x00400721 in main ()
(gdb) break func
Breakpoint 2 at 0x4006a1: func. (2 locations)
(gdb) continue
Continuing.
warning: GDB can't find the start of the function at 0x4006dd.
GDB is unable to find the start of the function at 0x4006dd
and thus can't determine the size of that function's stack frame.
This means that GDB may be unable to access that stack frame, or
the frames below it.
This problem is most likely caused by an invalid program counter or
stack pointer.
However, if you think GDB should simply search farther back
from 0x4006dd for code which looks like the beginning of a
function, you can increase the range of the search using the `set
heuristic-fence-post' command.
Program received signal SIGBUS, Bus error.
0x0040072b in main ()
(gdb) FAIL: gdb.dwarf2/dw2-skip-prologue.exp: continue to breakpoint: func
-- notice the breakpoint adjustment messages that are already a bad
sign. These happen when a breakpoint is requested in a branch delay
slot and are not supposed to happen unless explicitly requested with an
address pointing to a branch delay slot instruction. No symbol or line
debug information is supposed to direct GDB to place a breakpoint in a
delay slot.
Here's how `main' looks like:
00400718 <main>:
400718: 64f5 save 40,ra,s0-s1
40071a: 1a00 01a8 jal 4006a0 <func>
40071e: 0104 addiu s1,sp,16
400720: 1a00 01b7 jal 4006dc <func+0x3c>
400724: 6702 move s0,v0
400726: e049 addu v0,s0,v0
400728: 65b9 move sp,s1
40072a: 6473 restore 24,ra,s0-s1
40072c: e8a0 jrc ra
40072e: 6500 nop
-- so 0x400725 is the MIPS16 instruction address of the first MOVE
instruction seen above, in a delay slot of the preceding JAL instruction
indeed. This test case arranges for `main' to have no debug information
so it is one of the heuristic prologue scanners, `mips16_scan_prologue'
specifically in this case, that is responsible for finding the right
location for the breakpoint to place.
In this case the prologue really ends with the ADDIU instruction,
reordered into the delay slot of the first JAL instruction. Of course
we can't place the breakpoint for `main' after it as by doing so we'll
let `func' to be called before hitting this breakpoint. So the
breakpoint has to go at the JAL instruction instead, or 0x40071b.
To make a general case out of it we must never consider any jump or
branch instruction to be a part of a function's prologue. In the
presence of a jump or branch at the beginning of a function the furthest
instruction examined for the purpose of constructing frame information
can be one in the delay slot of that jump or branch if present, and
otherwise -- that is when the jump or branch is compact and has no delay
slot -- the instruction immediately preceding the jump or branch.
This change implements that approach across prologue scanners for the
three instruction ISAs. In implementing it I have factored out code
from the existing `*_instruction_has_delay_slot' handlers to be shared
and a side effect for the microMIPS implementation is it now always
fetches the second 16-bit halfword of 32-bit instructions even if it
eventually is not going to be needed. I think it's an acceptable
tradeoff for the purpose of code sharing.
To make things more consistent I also carried logic from
`micromips_scan_prologue' over to the other two scanners to accept (and
ignore) a single non-prologue non-control transfer instruction reordered
by the compiler into the prologue. While doing this I simplified the
exit path from the scan loop such that `end_prologue_addr' is set only
once. This made some concerns expressed in comments no longer
applicable, although even before they were not valid.
I have not fixed the logic around `load_immediate_bytes' in
`mips32_scan_prologue' though, it remains broken, although I took care
not to break it more. An approach similar to one taken for handling
larger stack adjustments in `micromips_scan_prologue' will have to be
eventually implemented here.
For regression testing I used my usual choice of the mips-linux-gnu
target and the following multilibs:
-EB
-EB -msoft-float
-EB -mips16
-EB -mips16 -msoft-float
-EB -mmicromips
-EB -mmicromips -msoft-float
-EB -mabi=n32
-EB -mabi=n32 -msoft-float
-EB -mabi=64
-EB -mabi=64 -msoft-float
and the -EL variants of same.
That removed gdb.dwarf2/dw2-skip-prologue.exp failures across MIPS16
multilibs, the test log now shows:
(gdb) file .../gdb.dwarf2/dw2-skip-prologue
Reading symbols from .../gdb.d/gdb.dwarf2/dw2-skip-prologue...done.
(gdb) delete breakpoints
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) break main
Breakpoint 1 at 0x40071b
(gdb) set remotetimeout 5
(gdb) kill
The program is not being run.
(gdb)
[...]
target remote ...:2345
Reading symbols from .../mips16/lib/ld.so.1...done.
0x2aaa8e81 in __start () from .../mips16/lib/ld.so.1
(gdb) continue
Continuing.
Breakpoint 1, 0x0040071b in main ()
(gdb) break func
Breakpoint 2 at 0x4006a1: func. (2 locations)
(gdb) continue
Continuing.
Breakpoint 2, func (param=0) at main.c:5
5 This program is free software; you can redistribute it and/or modify
(gdb) PASS: gdb.dwarf2/dw2-skip-prologue.exp: continue to breakpoint: func
-- so things look like intended.
That also did regress, again across MIPS16 multilibs, another test case,
gdb.base/step-symless.exp:
(gdb) file .../gdb.d/gdb.base/step-symless
Reading symbols from .../gdb.base/step-symless...done.
(gdb) delete breakpoints
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) break main
Breakpoint 1 at 0x4006d3
(gdb) set remotetimeout 5
(gdb) kill
The program is not being run.
(gdb)
[...]
target remote ...:2345
Reading symbols from .../mips16/lib/ld.so.1...done.
0x2aaa8e81 in __start () from .../mips16/lib/ld.so.1
(gdb) continue
Continuing.
Breakpoint 1, 0x004006d3 in main ()
(gdb) break symful
Breakpoint 2 at 0x4006a5
(gdb) step
Single stepping until exit from function main,
which has no line number information.
warning: GDB can't find the start of the function at 0x4006b9.
GDB is unable to find the start of the function at 0x4006b9
and thus can't determine the size of that function's stack frame.
This means that GDB may be unable to access that stack frame, or
the frames below it.
This problem is most likely caused by an invalid program counter or
stack pointer.
However, if you think GDB should simply search farther back
from 0x4006b9 for code which looks like the beginning of a
function, you can increase the range of the search using the `set
heuristic-fence-post' command.
0x004006b9 in ?? ()
(gdb) FAIL: gdb.base/step-symless.exp: step
-- but that is actually a good sign. Here `main', again, has no debug
information and code involved looks like:
004006a0 <symful>:
4006a0: 6491 save 8,s1
4006a2: 673d move s1,sp
4006a4: b204 lw v0,4006b4 <symful+0x14>
4006a6: 9a40 lw v0,0(v0)
4006a8: 4261 addiu v1,v0,1
4006aa: b203 lw v0,4006b4 <symful+0x14>
4006ac: da60 sw v1,0(v0)
4006ae: 65b9 move sp,s1
4006b0: 6411 restore 8,s1
4006b2: e8a0 jrc ra
4006b4: 0041 addiu s0,sp,260
4006b6: 0860 la s0,400834 <__libc_start_main@mips16plt+0x54>
4006b8: 6491 save 8,s1
4006ba: 673d move s1,sp
4006bc: b204 lw v0,4006cc <symful+0x2c>
4006be: 9a40 lw v0,0(v0)
4006c0: 4261 addiu v1,v0,1
4006c2: b203 lw v0,4006cc <symful+0x2c>
4006c4: da60 sw v1,0(v0)
4006c6: 65b9 move sp,s1
4006c8: 6411 restore 8,s1
4006ca: e8a0 jrc ra
4006cc: 0041 addiu s0,sp,260
4006ce: 0860 la s0,40084c <__libc_start_main@mips16plt+0x6c>
004006d0 <main>:
4006d0: 64d4 save 32,ra,s1
4006d2: 1a00 01ae jal 4006b8 <symful+0x18>
4006d6: 0104 addiu s1,sp,16
4006d8: 1a00 01a8 jal 4006a0 <symful>
4006dc: 6500 nop
4006de: 6740 move v0,zero
4006e0: 65b9 move sp,s1
4006e2: 6452 restore 16,ra,s1
4006e4: e8a0 jrc ra
4006e6: 6500 nop
4006e8: 6500 nop
4006ea: 6500 nop
4006ec: 6500 nop
4006ee: 6500 nop
-- and the original log:
(gdb) file .../gdb.base/step-symless
Reading symbols from .../gdb.base/step-symless...done.
(gdb) delete breakpoints
(gdb) info breakpoints
No breakpoints or watchpoints.
(gdb) break main
warning: Breakpoint address adjusted from 0x004006dd to 0x004006d9.
Breakpoint 1 at 0x4006d9
(gdb) set remotetimeout 5
(gdb) kill
The program is not being run.
(gdb)
[...]
target remote ...:2345
Reading symbols from .../mips16/lib/ld.so.1...done.
warning: Breakpoint address adjusted from 0x004006dd to 0x004006d9.
warning: Breakpoint address adjusted from 0x004006dd to 0x004006d9.
0x2aaa8e81 in __start () from .../mips16/lib/ld.so.1
(gdb) continue
Continuing.
warning: Breakpoint address adjusted from 0x004006dd to 0x004006d9.
warning: Breakpoint 1 address previously adjusted from 0x004006dd to
0x004006d9.
Breakpoint 1, 0x004006d9 in main ()
(gdb) break symful
Breakpoint 2 at 0x4006a5
(gdb) step
Single stepping until exit from function main,
which has no line number information.
Breakpoint 2, 0x004006a5 in symful ()
(gdb) PASS: gdb.base/step-symless.exp: step
So the breakpoint at `main' was actually set at an instruction after the
call to `symful+0x18' aka `symless' and the test only passed because
single-stepping through `symless' wasn't actually done at all. With
this change in place this test fails for MIPS16 multilibs consistently
with all the other multilibs where it already failed in this manner
previously.
* mips-tdep.c (mips16_instruction_is_compact_branch): New
function.
(micromips_instruction_is_compact_branch): Likewise.
(mips16_scan_prologue): Terminate scanning upon seeing a branch
or a compact jump, reaching a jump delay slot, or seeing a
second non-prologue instruction.
(micromips_scan_prologue): Also terminate scanning upon seeing a
compact branch or jump, or reaching a branch or jump delay slot.
(mips32_scan_prologue): Terminate scanning upon reaching a branch
or jump delay slot, or seeing a second non-prologue instruction.
(mips32_instruction_has_delay_slot): Retain instruction
examination code only, update arguments accordingly and move
instruction fetch pieces to...
(mips32_insn_at_pc_has_delay_slot): ... this new function.
(micromips_instruction_has_delay_slot): Likewise and to...
(micromips_insn_at_pc_has_delay_slot): ... this new function.
(mips16_instruction_has_delay_slot): Likewise and to...
(mips16_insn_at_pc_has_delay_slot): ... this new function.
(mips_single_step_through_delay): Update accordingly.
(mips_adjust_breakpoint_address): Likewise.
README for GNU development tools
This directory contains various GNU compilers, assemblers, linkers,
debuggers, etc., plus their support routines, definitions, and documentation.
If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README; if with a libg++ release,
see libg++/README, etc. That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.
It is now possible to automatically configure and build a variety of
tools with one command. To build all of the tools contained herein,
run the ``configure'' script here, e.g.:
./configure
make
To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
make install
(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''. You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)
If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make. For example (assuming sh/bash/ksh):
CC=gcc ./configure
make
A similar example using csh:
setenv CC gcc
./configure
make
Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc. See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.
REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.
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