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bfd/COFF: propagate function size when copying/linking ELF objects

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While COFF, unlike ELF, doesn't have a generic way to express symbol
size, there is a means to do so for functions. When inputs are ELF,
propagate function sizes, including the fact that a symbol denotes a
function, to the output's symbol table.

Note that this requires hackery (cross-object-format processing) in two
places - when linking, global symbols are entered into a global hash
table, and hence relevant information needs to be updated there in that
case, while otherwise the original symbol structures can be consulted.

For the setting of ->u.syment.n_type the later writing of the field to
literal 0 needs to be dropped from coff_write_alien_symbol(). It was
redundant anyway with an earlier write of the field using C_NUL.
This commit is contained in:
Jan Beulich
2025-04-14 14:22:49 +02:00
parent 55cee09736
commit 06d3221915
2 changed files with 60 additions and 5 deletions
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18
bfd/coffgen.c
View File

@@ -42,6 +42,7 @@
#include "libbfd.h"
#include "coff/internal.h"
#include "libcoff.h"
#include "elf-bfd.h"
#include "hashtab.h"
/* Extract a long section name at STRINDEX and copy it to the bfd objstack.
@@ -1270,9 +1271,24 @@ coff_write_alien_symbol (bfd *abfd,
if (c != (coff_symbol_type *) NULL)
native->u.syment.n_flags = bfd_asymbol_bfd (&c->symbol)->flags;
}
const elf_symbol_type *elfsym = elf_symbol_from (symbol);
if (elfsym
&& (symbol->flags & BSF_FUNCTION)
&& elfsym->internal_elf_sym.st_size)
{
/* coff_data (abfd)->local_n_btshft is what ought to be used here,
just that it's set only when reading in COFF objects. */
native->u.syment.n_type = DT_FCN << 4;
native->u.syment.n_numaux = 1;
native[1].u.auxent.x_sym.x_misc.x_fsize
= elfsym->internal_elf_sym.st_size;
/* FIXME .u.auxent.x_sym.x_fcnary.x_fcn.x_endndx would better also
be set, which would require updating the field once the next
function is seen. */
}
}
native->u.syment.n_type = 0;
if (symbol->flags & BSF_FILE)
native->u.syment.n_sclass = C_FILE;
else if (symbol->flags & BSF_LOCAL)

43
bfd/cofflink.c
View File

@@ -27,6 +27,7 @@
#include "libbfd.h"
#include "coff/internal.h"
#include "libcoff.h"
#include "elf-bfd.h"
#include "safe-ctype.h"
static bool coff_link_add_object_symbols (bfd *, struct bfd_link_info *);
@@ -931,14 +932,52 @@ _bfd_coff_final_link (bfd *abfd,
bfd_vma written = 0;
bool rewrite = false;
if (! (sym->flags & BSF_LOCAL)
|| (sym->flags & (BSF_SECTION_SYM | BSF_DEBUGGING_RELOC
if ((sym->flags & (BSF_SECTION_SYM | BSF_DEBUGGING_RELOC
| BSF_THREAD_LOCAL | BSF_RELC | BSF_SRELC
| BSF_SYNTHETIC))
|| ((sym->flags & BSF_DEBUGGING)
&& ! (sym->flags & BSF_FILE)))
continue;
if (! (sym->flags & BSF_LOCAL))
{
/* For ELF symbols try to represent their function-ness and
size, if available. */
if (! (sym->flags & BSF_FUNCTION))
continue;
const elf_symbol_type *elfsym = elf_symbol_from (sym);
if (!elfsym)
continue;
struct coff_link_hash_entry *hent
= (struct coff_link_hash_entry *) bfd_hash_lookup
(&info->hash->table, bfd_asymbol_name (sym),
false, false);
if (!hent)
continue;
/* coff_data (abfd)->local_n_btshft is what ought to be used
here, just that it's set only when reading in COFF
objects. */
hent->type = DT_FCN << 4;
if (!elfsym->internal_elf_sym.st_size)
continue;
hent->aux = bfd_zalloc (abfd, sizeof (*hent->aux));
if (!hent->aux)
continue;
hent->numaux = 1;
hent->aux->x_sym.x_misc.x_fsize
= elfsym->internal_elf_sym.st_size;
/* FIXME ->x_sym.x_fcnary.x_fcn.x_endndx would better
also be set, yet that would likely need to happen
elsewhere anyway. */
continue;
}
/* See if we are discarding symbols with this name. */
if ((flaginfo.info->strip == strip_some
&& (bfd_hash_lookup (flaginfo.info->keep_hash,