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Extend pdp11-aout symbol table format and code for .stab symbols. 

* bfd/pdp11.c (pdp11_external_nlist): Repurposed e_unused to e_desc.
(N_STAB, is_stab): Needed new function is_stab to disambiguate
normal vs. .stab symbol table type values, replacing N_STAB mask.
(translate_from_native_sym_flags): Determine correct section for
different .stab types.
(translate_to_native_sym_flags): Leave .stab types intact.
(translate_symbol_table): Error if symbol indicates overlay;
store desc field from .stab symbols.
(write_syms): Output desc field with symbol.
(aout_link_check_ar_symbols): Skip .stab symbols.
(aout_link_add_symbols): Correctly distinguish .stab symbols.
(aout_link_write_other_symbol): Write 0 for desk and ovly fields.
(aout_link_write_symbols): Write 0 for desk and ovly fields;
correctly distinguish .stab symbols and select calculate their
section and value; and copy desc and ovly fields from input symbol
to output symbol.
This commit is contained in:
Stephen Casner 2020-06-04 18:12:32 -07:00
parent 470e738f6d
commit a975c88e65
2 changed files with 146 additions and 31 deletions
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22
bfd/ChangeLog
View File

@ -1,3 +1,25 @@
2020-06-04 Stephen Casner <casner@acm.org>
Extend pdp11-aout symbol table format to accommodate .stab
symbols and implement correct handling of them.
* pdp11.c (pdp11_external_nlist): Repurposed e_unused to e_desc.
(N_STAB, is_stab): Needed new function is_stab to disambiguate
normal vs. .stab symbol table type values, replacing N_STAB mask.
(translate_from_native_sym_flags): Determine correct section for
different .stab types.
(translate_to_native_sym_flags): Leave .stab types intact.
(translate_symbol_table): Error if symbol indicates overlay;
store desc field from .stab symbols.
(write_syms): Output desc field with symbol.
(aout_link_check_ar_symbols): Skip .stab symbols.
(aout_link_add_symbols): Correctly distinguish .stab symbols.
(aout_link_write_other_symbol): Write 0 for desk and ovly fields.
(aout_link_write_symbols): Write 0 for desk and ovly fields;
correctly distinguish .stab symbols and select calculate their
section and value; and copy desc and ovly fields from input symbol
to output symbol.
2020-06-04 Stephen Casner <casner@acm.org>
* aoutx.h (translate_symbol_table): Comment had external and

155
bfd/pdp11.c
View File

@ -22,7 +22,9 @@
/* BFD backend for PDP-11, running 2.11BSD in particular.
This file was hacked up by looking hard at the existing vaxnetbsd
back end and the header files in 2.11BSD.
back end and the header files in 2.11BSD. The symbol table format
of 2.11BSD has been extended to accommodate .stab symbols. See
struct pdp11_external_nlist below for details.
TODO
* support for V7 file formats
@ -101,10 +103,23 @@ struct pdp11_external_exec
#define A_FLAG_RELOC_STRIPPED 0x0001
/* The following struct defines the format of an entry in the object file
symbol table. In the original 2.11BSD struct the index into the string
table is stored as a long, but the PDP11 C convention for storing a long in
memory placed the most significant word first even though the bytes within a
word are stored least significant first. So here the string table index is
considered to be just 16 bits and the first two bytes of the struct were
previously named e_unused. To extend the symbol table format to accommodate
.stab symbols, the e_unused bytes are renamed e_desc to store the desc field
of the .stab symbol. The GDP Project's STABS document says that the "other"
field is almost always unused and can be set to zero; the only nonzero cases
identified were for stabs in their own sections, which does not apply for
pdp11 a.out format, and for a special case of GNU Modula2 which is not
supported for the PDP11. */
#define external_nlist pdp11_external_nlist
struct pdp11_external_nlist
{
bfd_byte e_unused[2]; /* Unused. */
bfd_byte e_desc[2]; /* The desc field for .stab symbols, else 0. */
bfd_byte e_strx[2]; /* Index into string table of name. */
bfd_byte e_type[1]; /* Type of symbol. */
bfd_byte e_ovly[1]; /* Overlay number. */
@ -151,6 +166,13 @@ static bfd_boolean MY(write_object_contents) (bfd *);
#include "aout/stab_gnu.h"
#include "aout/ar.h"
/* The symbol type numbers for the 16-bit a.out format from 2.11BSD differ from
those defined in aout64.h so we must redefine them here. N_EXT changes from
0x01 to 0x20 which creates a conflict with some .stab values, in particular
between undefined externals (N_UNDF+N_EXT) vs. global variables (N_GYSM) and
between external bss symbols (N_BSS+N_EXT) vs. function names (N_FUN). We
disambiguate those conflicts with a hack in is_stab() to look for the ':' in
the global variable or function name string. */
#undef N_TYPE
#undef N_UNDF
#undef N_ABS
@ -170,7 +192,12 @@ static bfd_boolean MY(write_object_contents) (bfd *);
#define N_REG 0x14 /* Register symbol. */
#define N_FN 0x1f /* File name. */
#define N_EXT 0x20 /* External flag. */
#define N_STAB 0xc0 /* Not relevant; modified aout64.h's 0xe0 to avoid N_EXT. */
/* Type numbers from .stab entries that could conflict:
N_GSYM 0x20 Global variable [conflict with external undef]
N_FNAME 0x22 Function name (for BSD Fortran) [ignored]
N_FUN 0x24 Function name [conflict with external BSS]
N_NOMAP 0x34 No DST map for sym. [ext. reg. doesn't exist]
*/
#define RELOC_SIZE 2
@ -300,6 +327,19 @@ NAME (aout, reloc_name_lookup) (bfd *abfd ATTRIBUTE_UNUSED,
return NULL;
}
/* Disambiguate conflicts between normal symbol types and .stab symbol types
(undefined externals N_UNDF+N_EXT vs. global variables N_GYSM and external
bss symbols N_BSS+N_EXT vs. function names N_FUN) with a hack to look for
the ':' in the global variable or function name string. */
static int
is_stab (int type, const char *name)
{
if (type == N_GSYM || type == N_FUN)
return (index(name, ':') != NULL);
return (type > N_FUN);
}
static int
pdp11_aout_write_headers (bfd *abfd, struct internal_exec *execp)
{
@ -1325,7 +1365,7 @@ translate_from_native_sym_flags (bfd *abfd,
{
flagword visible;
if (cache_ptr->type == N_FN)
if (is_stab (cache_ptr->type, cache_ptr->symbol.name))
{
asection *sec;
@ -1333,20 +1373,25 @@ translate_from_native_sym_flags (bfd *abfd,
cache_ptr->symbol.flags = BSF_DEBUGGING;
/* Work out the symbol section. */
switch (cache_ptr->type & N_TYPE)
switch (cache_ptr->type)
{
case N_TEXT:
case N_SO:
case N_SOL:
case N_FUN:
case N_ENTRY:
case N_SLINE:
case N_FN:
sec = obj_textsec (abfd);
break;
case N_DATA:
case N_STSYM:
case N_DSLINE:
sec = obj_datasec (abfd);
break;
case N_BSS:
case N_LCSYM:
case N_BSLINE:
sec = obj_bsssec (abfd);
break;
default:
case N_ABS:
sec = bfd_abs_section_ptr;
break;
}
@ -1418,10 +1463,12 @@ translate_to_native_sym_flags (bfd *abfd,
bfd_vma value = cache_ptr->value;
asection *sec;
bfd_vma off;
const char *name = cache_ptr->name != NULL ? cache_ptr->name : "*unknown*";
/* Mask out any existing type bits in case copying from one section
to another. */
sym_pointer->e_type[0] &= ~N_TYPE;
if (!is_stab (sym_pointer->e_type[0], name))
sym_pointer->e_type[0] &= ~N_TYPE;
sec = bfd_asymbol_section (cache_ptr);
off = 0;
@ -1433,7 +1480,7 @@ translate_to_native_sym_flags (bfd *abfd,
_bfd_error_handler
/* xgettext:c-format */
(_("%pB: can not represent section for symbol `%s' in a.out object file format"),
abfd, cache_ptr->name != NULL ? cache_ptr->name : "*unknown*");
abfd, name);
bfd_set_error (bfd_error_nonrepresentable_section);
return FALSE;
}
@ -1511,6 +1558,7 @@ NAME (aout, translate_symbol_table) (bfd *abfd,
for (; ext < ext_end; ext++, in++)
{
bfd_vma x;
int ovly;
x = GET_WORD (abfd, ext->e_strx);
in->symbol.the_bfd = abfd;
@ -1533,9 +1581,19 @@ NAME (aout, translate_symbol_table) (bfd *abfd,
return FALSE;
}
ovly = H_GET_8 (abfd, ext->e_ovly);
if (ovly != 0)
{
_bfd_error_handler
(_("%pB: symbol indicates overlay (not supported)"), abfd);
bfd_set_error (bfd_error_bad_value);
return FALSE;
}
in->symbol.value = GET_WORD (abfd, ext->e_value);
/* TODO: is 0 a safe value here? */
in->desc = 0;
/* e_desc is zero for normal symbols but for .stab symbols it
carries the desc field in our extended 2.11BSD format. */
in->desc = H_GET_16 (abfd, ext->e_desc);
in->other = 0;
in->type = H_GET_8 (abfd, ext->e_type);
in->symbol.udata.p = NULL;
@ -1686,23 +1744,27 @@ NAME (aout, write_syms) (bfd *abfd)
bfd_size_type indx;
struct external_nlist nsp;
PUT_WORD (abfd, 0, nsp.e_unused);
indx = add_to_stringtab (abfd, strtab, g->name, FALSE);
if (indx == (bfd_size_type) -1)
goto error_return;
PUT_WORD (abfd, indx, nsp.e_strx);
if (bfd_asymbol_flavour(g) == abfd->xvec->flavour)
H_PUT_8 (abfd, aout_symbol(g)->type, nsp.e_type);
{
H_PUT_16 (abfd, aout_symbol (g)->desc, nsp.e_desc);
H_PUT_8 (abfd, 0, nsp.e_ovly);
H_PUT_8 (abfd, aout_symbol (g)->type, nsp.e_type);
}
else
H_PUT_8 (abfd, 0, nsp.e_type);
{
H_PUT_16 (abfd, 0, nsp.e_desc);
H_PUT_8 (abfd, 0, nsp.e_ovly);
H_PUT_8 (abfd, 0, nsp.e_type);
}
if (! translate_to_native_sym_flags (abfd, g, &nsp))
goto error_return;
H_PUT_8 (abfd, 0, nsp.e_ovly);
if (bfd_bwrite ((void *)&nsp, (bfd_size_type) EXTERNAL_NLIST_SIZE, abfd)
!= EXTERNAL_NLIST_SIZE)
goto error_return;
@ -2643,17 +2705,17 @@ aout_link_check_ar_symbols (bfd *abfd,
for (; p < pend; p++)
{
int type = H_GET_8 (abfd, p->e_type);
const char *name;
const char *name = strings + GET_WORD (abfd, p->e_strx);
struct bfd_link_hash_entry *h;
/* Ignore symbols that are not externally visible. This is an
optimization only, as we check the type more thoroughly
below. */
if ((type & N_EXT) == 0
|| is_stab(type, name)
|| type == N_FN)
continue;
name = strings + GET_WORD (abfd, p->e_strx);
h = bfd_link_hash_lookup (info->hash, name, FALSE, FALSE, TRUE);
/* We are only interested in symbols that are currently
@ -2863,6 +2925,10 @@ aout_link_add_symbols (bfd *abfd, struct bfd_link_info *info)
type = H_GET_8 (abfd, p->e_type);
/* Ignore debugging symbols. */
if (is_stab(type, name))
continue;
/* PR 19629: Corrupt binaries can contain illegal string offsets. */
if (GET_WORD (abfd, p->e_strx) >= obj_aout_external_string_size (abfd))
return FALSE;
@ -2873,8 +2939,8 @@ aout_link_add_symbols (bfd *abfd, struct bfd_link_info *info)
switch (type)
{
default:
/* Anything else should be a debugging symbol. */
BFD_ASSERT ((type & N_STAB) != 0);
/* Shouldn't be any types not covered. */
BFD_ASSERT (0);
continue;
case N_UNDF:
@ -3077,12 +3143,14 @@ aout_link_write_other_symbol (struct bfd_hash_entry *bh, void *data)
}
H_PUT_8 (output_bfd, type, outsym.e_type);
H_PUT_8 (output_bfd, 0, outsym.e_ovly);
indx = add_to_stringtab (output_bfd, flaginfo->strtab, h->root.root.string,
FALSE);
if (indx == (bfd_size_type) -1)
/* FIXME: No way to handle errors. */
abort ();
PUT_WORD (output_bfd, 0, outsym.e_desc);
PUT_WORD (output_bfd, indx, outsym.e_strx);
PUT_WORD (output_bfd, val, outsym.e_value);
@ -4097,6 +4165,8 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
&& discard != discard_all)
{
H_PUT_8 (output_bfd, N_TEXT, outsym->e_type);
H_PUT_8 (output_bfd, 0, outsym->e_ovly);
H_PUT_16 (output_bfd, 0, outsym->e_desc);
strtab_index = add_to_stringtab (output_bfd, flaginfo->strtab,
bfd_get_filename (input_bfd), FALSE);
if (strtab_index == (bfd_size_type) -1)
@ -4210,7 +4280,7 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
case strip_none:
break;
case strip_debugger:
if ((type & N_STAB) != 0)
if (is_stab (type, name))
skip = TRUE;
break;
case strip_some:
@ -4230,7 +4300,33 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
}
/* Get the value of the symbol. */
if ((type & N_TYPE) == N_TEXT
if (is_stab (type, name))
{
switch (type)
{
default:
symsec = bfd_abs_section_ptr;
break;
case N_SO:
case N_SOL:
case N_FUN:
case N_ENTRY:
case N_SLINE:
case N_FN:
symsec = obj_textsec (input_bfd);
break;
case N_STSYM:
case N_DSLINE:
symsec = obj_datasec (input_bfd);
break;
case N_LCSYM:
case N_BSLINE:
symsec = obj_bsssec (input_bfd);
break;
}
val = GET_WORD (input_bfd, sym->e_value);
}
else if ((type & N_TYPE) == N_TEXT
|| type == N_WEAKT)
symsec = obj_textsec (input_bfd);
else if ((type & N_TYPE) == N_DATA
@ -4258,11 +4354,6 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
val = GET_WORD (input_bfd, sym->e_value);
symsec = NULL;
}
else if ((type & N_STAB) != 0)
{
val = GET_WORD (input_bfd, sym->e_value);
symsec = NULL;
}
else
{
/* If we get here with an indirect symbol, it means that
@ -4376,7 +4467,7 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
case discard_sec_merge:
break;
case discard_l:
if ((type & N_STAB) == 0
if (!is_stab (type, name)
&& bfd_is_local_label_name (input_bfd, name))
skip = TRUE;
break;
@ -4500,6 +4591,8 @@ aout_link_write_symbols (struct aout_final_link_info *flaginfo, bfd *input_bfd)
/* Copy this symbol into the list of symbols we are going to
write out. */
H_PUT_8 (output_bfd, type, outsym->e_type);
H_PUT_8 (output_bfd, H_GET_8 (input_bfd, sym->e_ovly), outsym->e_ovly);
H_PUT_16 (output_bfd, H_GET_16 (input_bfd, sym->e_desc), outsym->e_desc);
copy = FALSE;
if (! flaginfo->info->keep_memory)
{