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elfcopy: delete filter_reloc, it is broken and unnecessary

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elfcopy contained logic to filter individual relocations in STRIP_ALL
mode.  However, this is not valid; relocations emitted by the linker are
required, unless they apply to an entire section being removed (which is
handled by other logic in elfcopy).

Note that filter_reloc was also buggy: for RELA relocation sections it
operated on uninitialized rel.r_info resulting in invalid operation.

The logic most likely needs to be inverted: instead of removing
relocations because their associated symbols are being removed, we must
keep symbols referenced by relocations.  That said, in practice we do
not encounter this code path today: objects being stripped are either
dynamically linked binaries which retain .dynsym, or static binaries
with no relocations.

Just remove filter_reloc.  This fixes certain cases including statically
linked binaries containing ifuncs.  Stripping binaries with relocations
referencing removed symbols was already broken, and after this change
may still be broken in a different way.

PR:		232176
Reviewed by:	kaiw, kib, markj
Approved by:	re (rgrimes)
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D17519
This commit is contained in:
Ed Maste 2018-10-13 21:26:07 +00:00
parent 6816c88458
commit c9504239e8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339350
1 changed files with 0 additions and 128 deletions
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128
contrib/elftoolchain/elfcopy/sections.c
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@ -39,7 +39,6 @@ ELFTC_VCSID("$Id: sections.c 3443 2016-04-15 18:57:54Z kaiwang27 $");
static void add_gnu_debuglink(struct elfcopy *ecp);
static uint32_t calc_crc32(const char *p, size_t len, uint32_t crc);
static void check_section_rename(struct elfcopy *ecp, struct section *s);
static void filter_reloc(struct elfcopy *ecp, struct section *s);
static int get_section_flags(struct elfcopy *ecp, const char *name);
static void insert_sections(struct elfcopy *ecp);
static void insert_to_strtab(struct section *t, const char *s);
@ -573,14 +572,6 @@ copy_content(struct elfcopy *ecp)
strcmp(s->name, ".shstrtab") == 0)
continue;
/*
* If strip action is STRIP_ALL, relocation info need
* to be stripped. Skip filtering otherwisw.
*/
if (ecp->strip == STRIP_ALL &&
(s->type == SHT_REL || s->type == SHT_RELA))
filter_reloc(ecp, s);
/*
* The section indices in the SHT_GROUP section needs
* to be updated since we might have stripped some
@ -673,125 +664,6 @@ update_section_group(struct elfcopy *ecp, struct section *s)
s->nocopy = 1;
}
/*
* Filter relocation entries, only keep those entries whose
* symbol is in the keep list.
*/
static void
filter_reloc(struct elfcopy *ecp, struct section *s)
{
const char *name;
GElf_Shdr ish;
GElf_Rel rel;
GElf_Rela rela;
Elf32_Rel *rel32;
Elf64_Rel *rel64;
Elf32_Rela *rela32;
Elf64_Rela *rela64;
Elf_Data *id;
uint64_t cap, n, nrels;
int elferr, i;
if (gelf_getshdr(s->is, &ish) == NULL)
errx(EXIT_FAILURE, "gelf_getehdr() failed: %s",
elf_errmsg(-1));
/* We don't want to touch relocation info for dynamic symbols. */
if ((ecp->flags & SYMTAB_EXIST) == 0) {
if (ish.sh_link == 0 || ecp->secndx[ish.sh_link] == 0) {
/*
* This reloc section applies to the symbol table
* that was stripped, so discard whole section.
*/
s->nocopy = 1;
s->sz = 0;
}
return;
} else {
/* Symbol table exist, check if index equals. */
if (ish.sh_link != elf_ndxscn(ecp->symtab->is))
return;
}
#define COPYREL(REL, SZ) do { \
if (nrels == 0) { \
if ((REL##SZ = malloc(cap * \
sizeof(*REL##SZ))) == NULL) \
err(EXIT_FAILURE, "malloc failed"); \
} \
if (nrels >= cap) { \
cap *= 2; \
if ((REL##SZ = realloc(REL##SZ, cap * \
sizeof(*REL##SZ))) == NULL) \
err(EXIT_FAILURE, "realloc failed"); \
} \
REL##SZ[nrels].r_offset = REL.r_offset; \
REL##SZ[nrels].r_info = REL.r_info; \
if (s->type == SHT_RELA) \
rela##SZ[nrels].r_addend = rela.r_addend; \
nrels++; \
} while (0)
nrels = 0;
cap = 4; /* keep list is usually small. */
rel32 = NULL;
rel64 = NULL;
rela32 = NULL;
rela64 = NULL;
if ((id = elf_getdata(s->is, NULL)) == NULL)
errx(EXIT_FAILURE, "elf_getdata() failed: %s",
elf_errmsg(-1));
n = ish.sh_size / ish.sh_entsize;
for(i = 0; (uint64_t)i < n; i++) {
if (s->type == SHT_REL) {
if (gelf_getrel(id, i, &rel) != &rel)
errx(EXIT_FAILURE, "gelf_getrel failed: %s",
elf_errmsg(-1));
} else {
if (gelf_getrela(id, i, &rela) != &rela)
errx(EXIT_FAILURE, "gelf_getrel failed: %s",
elf_errmsg(-1));
}
name = elf_strptr(ecp->ein, elf_ndxscn(ecp->strtab->is),
GELF_R_SYM(rel.r_info));
if (name == NULL)
errx(EXIT_FAILURE, "elf_strptr failed: %s",
elf_errmsg(-1));
if (lookup_symop_list(ecp, name, SYMOP_KEEP) != NULL) {
if (ecp->oec == ELFCLASS32) {
if (s->type == SHT_REL)
COPYREL(rel, 32);
else
COPYREL(rela, 32);
} else {
if (s->type == SHT_REL)
COPYREL(rel, 64);
else
COPYREL(rela, 64);
}
}
}
elferr = elf_errno();
if (elferr != 0)
errx(EXIT_FAILURE, "elf_getdata() failed: %s",
elf_errmsg(elferr));
if (ecp->oec == ELFCLASS32) {
if (s->type == SHT_REL)
s->buf = rel32;
else
s->buf = rela32;
} else {
if (s->type == SHT_REL)
s->buf = rel64;
else
s->buf = rela64;
}
s->sz = gelf_fsize(ecp->eout, (s->type == SHT_REL ? ELF_T_REL :
ELF_T_RELA), nrels, EV_CURRENT);
s->nocopy = 1;
}
static void
update_reloc(struct elfcopy *ecp, struct section *s)
{