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libctf, open: fix opening CTF in binaries with no symtab

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This is a perfectly possible case, and half of ctf_bfdopen_ctfsect
handled it fine.  The other half hit a divide by zero or two before we
got that far, and had no code path to load the strtab from anywhere
in the absence of a symtab to point at it in any case.

So, as a fallback, if there is no symtab, try loading ".strtab"
explicitly by name, like we used to before we started looking for the
strtab the symtab used.

Of course, such a strtab is not kept hold of by BFD, so this means we
have to bring back the code to possibly explicitly free the strtab that
we read in.

libctf/
	* ctf-impl.h (struct ctf_archive_internal) <ctfi_free_strsect>
	New.
	* ctf-open-bfd.c (ctf_bfdopen_ctfsect): Explicitly open a strtab
	if the input has no symtab, rather than dividing by
	zero. Arrange to free it later via ctfi_free_ctfsect.
	* ctf-archive.c (ctf_new_archive_internal): Do not
	ctfi_free_strsect by default.
	(ctf_arc_close): Possibly free it here.
This commit is contained in:
Nick Alcock 2020-06-09 10:27:57 +01:00
parent 7044740174
commit d50c08025d
4 changed files with 73 additions and 29 deletions
Download patch file Download diff file Expand all files Collapse all files

87
libctf/ctf-open-bfd.c
View file

@ -94,46 +94,69 @@ ctf_bfdopen_ctfsect (struct bfd *abfd _libctf_unused_,
ctf_sect_t *symsectp = NULL;
ctf_sect_t *strsectp = NULL;
const char *bfderrstr = NULL;
char *strtab_alloc = NULL;
#ifdef HAVE_BFD_ELF
ctf_sect_t symsect, strsect;
Elf_Internal_Shdr *strhdr;
Elf_Internal_Shdr *symhdr = &elf_symtab_hdr (abfd);
size_t symcount = symhdr->sh_size / symhdr->sh_entsize;
size_t symcount;
Elf_Internal_Sym *isymbuf;
bfd_byte *symtab;
bfd_byte *symtab = NULL;
const char *strtab = NULL;
size_t strsize;
/* TODO: handle SYMTAB_SHNDX. */
if ((symtab = malloc (symhdr->sh_size)) == NULL)
/* Get the symtab, and the strtab associated with it. */
if (elf_tdata (abfd) && symhdr && symhdr->sh_size && symhdr->sh_entsize)
{
bfderrstr = "Cannot malloc symbol table";
goto err;
}
isymbuf = bfd_elf_get_elf_syms (abfd, symhdr, symcount, 0,
NULL, symtab, NULL);
free (isymbuf);
if (isymbuf == NULL)
{
bfderrstr = "Cannot read symbol table";
goto err_free_sym;
}
if (elf_elfsections (abfd) != NULL
&& symhdr->sh_link < elf_numsections (abfd))
{
strhdr = elf_elfsections (abfd)[symhdr->sh_link];
if (strhdr->contents == NULL)
symcount = symhdr->sh_size / symhdr->sh_entsize;
if ((symtab = malloc (symhdr->sh_size)) == NULL)
{
if ((strtab = bfd_elf_get_str_section (abfd, symhdr->sh_link)) == NULL)
bfderrstr = "Cannot malloc symbol table";
goto err;
}
isymbuf = bfd_elf_get_elf_syms (abfd, symhdr, symcount, 0,
NULL, symtab, NULL);
free (isymbuf);
if (isymbuf == NULL)
{
bfderrstr = "Cannot read symbol table";
goto err_free_sym;
}
if (elf_elfsections (abfd) != NULL
&& symhdr->sh_link < elf_numsections (abfd))
{
Elf_Internal_Shdr *strhdr = elf_elfsections (abfd)[symhdr->sh_link];
strsize = strhdr->sh_size;
if (strhdr->contents == NULL)
{
bfderrstr = "Cannot read string table";
goto err_free_sym;
if ((strtab = bfd_elf_get_str_section (abfd, symhdr->sh_link)) == NULL)
{
bfderrstr = "Cannot read string table";
goto err_free_sym;
}
}
else
strtab = (const char *) strhdr->contents;
}
}
else /* No symtab: just try getting .strtab by name. */
{
bfd_byte *str_bcontents;
asection *str_asect;
if ((str_asect = bfd_get_section_by_name (abfd, ".strtab")) != NULL)
{
if (bfd_malloc_and_get_section (abfd, str_asect, &str_bcontents))
{
strtab = (const char *) str_bcontents;
strtab_alloc = (char *) str_bcontents;
strsize = str_asect->size;
}
}
else
strtab = (const char *) strhdr->contents;
}
if (strtab)
@ -144,9 +167,12 @@ ctf_bfdopen_ctfsect (struct bfd *abfd _libctf_unused_,
strsect.cts_data = strtab;
strsect.cts_name = ".strtab";
strsect.cts_size = strhdr->sh_size;
strsect.cts_size = strsize;
strsectp = &strsect;
}
if (symtab)
{
assert (symhdr->sh_entsize == get_elf_backend_data (abfd)->s->sizeof_sym);
symsect.cts_name = ".symtab";
symsect.cts_entsize = symhdr->sh_entsize;
@ -159,13 +185,16 @@ ctf_bfdopen_ctfsect (struct bfd *abfd _libctf_unused_,
arci = ctf_arc_bufopen (ctfsect, symsectp, strsectp, errp);
if (arci)
{
/* Request freeing of the symsect. */
/* Request freeing of the symsect and possibly the strsect. */
arci->ctfi_free_symsect = 1;
if (strtab_alloc)
arci->ctfi_free_strsect = 1;
return arci;
}
#ifdef HAVE_BFD_ELF
err_free_sym:
free (symtab);
free (strtab_alloc);
#endif
err: _libctf_unused_;
if (bfderrstr)