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make relocation time symbol lookup and dlsym consistent

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Using common code path for all symbol lookups fixes three dlsym issues:

- st_shndx of STT_TLS symbols were not checked and thus an undefined
  tls symbol reference could be incorrectly treated as a definition
  (the sysv hash lookup returns undefined symbols, gnu does not, so should
  be rare in practice).

- symbol binding was not checked so a hidden symbol may be returned
  (in principle STB_LOCAL symbols may appear in the dynamic symbol table
  for hidden symbols, but linkers most likely don't produce it).

- mips specific behaviour was not applied (ARCH_SYM_REJECT_UND) so
  undefined symbols may be returned on mips.

always_inline is used to avoid relocation performance regression, the
code generation for find_sym should not be affected.
This commit is contained in:
Szabolcs Nagy 2019-08-10 23:14:40 +00:00 committed by Rich Felker
parent 1f060ed2fb
commit f2435263d7
1 changed files with 30 additions and 52 deletions
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82
ldso/dynlink.c
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@ -283,12 +283,16 @@ static Sym *gnu_lookup_filtered(uint32_t h1, uint32_t *hashtab, struct dso *dso,
#define ARCH_SYM_REJECT_UND(s) 0
#endif
static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
#if defined(__GNUC__)
__attribute__((always_inline))
#endif
static inline struct symdef find_sym2(struct dso *dso, const char *s, int need_def, int use_deps)
{
uint32_t h = 0, gh = gnu_hash(s), gho = gh / (8*sizeof(size_t)), *ght;
size_t ghm = 1ul << gh % (8*sizeof(size_t));
struct symdef def = {0};
for (; dso; dso=dso->syms_next) {
struct dso **deps = use_deps ? dso->deps : 0;
for (; dso; dso=use_deps ? *deps++ : dso->syms_next) {
Sym *sym;
if ((ght = dso->ghashtab)) {
sym = gnu_lookup_filtered(gh, ght, dso, s, gho, ghm);
@ -313,6 +317,11 @@ static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
return def;
}
static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
{
return find_sym2(dso, s, need_def, 0);
}
static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stride)
{
unsigned char *base = dso->base;
@ -2123,58 +2132,27 @@ static void *addr2dso(size_t a)
static void *do_dlsym(struct dso *p, const char *s, void *ra)
{
size_t i;
uint32_t h = 0, gh = 0, *ght;
Sym *sym;
if (p == head || p == RTLD_DEFAULT || p == RTLD_NEXT) {
if (p == RTLD_DEFAULT) {
p = head;
} else if (p == RTLD_NEXT) {
p = addr2dso((size_t)ra);
if (!p) p=head;
p = p->next;
}
struct symdef def = find_sym(p, s, 0);
if (!def.sym) goto failed;
if ((def.sym->st_info&0xf) == STT_TLS)
return __tls_get_addr((tls_mod_off_t []){def.dso->tls_id, def.sym->st_value-DTP_OFFSET});
if (DL_FDPIC && (def.sym->st_info&0xf) == STT_FUNC)
return def.dso->funcdescs + (def.sym - def.dso->syms);
return laddr(def.dso, def.sym->st_value);
}
if (__dl_invalid_handle(p))
int use_deps = 0;
if (p == head || p == RTLD_DEFAULT) {
p = head;
} else if (p == RTLD_NEXT) {
p = addr2dso((size_t)ra);
if (!p) p=head;
p = p->next;
} else if (__dl_invalid_handle(p)) {
return 0;
} else
use_deps = 1;
struct symdef def = find_sym2(p, s, 0, use_deps);
if (!def.sym) {
error("Symbol not found: %s", s);
return 0;
if ((ght = p->ghashtab)) {
gh = gnu_hash(s);
sym = gnu_lookup(gh, ght, p, s);
} else {
h = sysv_hash(s);
sym = sysv_lookup(s, h, p);
}
if (sym && (sym->st_info&0xf) == STT_TLS)
return __tls_get_addr((tls_mod_off_t []){p->tls_id, sym->st_value-DTP_OFFSET});
if (DL_FDPIC && sym && sym->st_shndx && (sym->st_info&0xf) == STT_FUNC)
return p->funcdescs + (sym - p->syms);
if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
return laddr(p, sym->st_value);
for (i=0; p->deps[i]; i++) {
if ((ght = p->deps[i]->ghashtab)) {
if (!gh) gh = gnu_hash(s);
sym = gnu_lookup(gh, ght, p->deps[i], s);
} else {
if (!h) h = sysv_hash(s);
sym = sysv_lookup(s, h, p->deps[i]);
}
if (sym && (sym->st_info&0xf) == STT_TLS)
return __tls_get_addr((tls_mod_off_t []){p->deps[i]->tls_id, sym->st_value-DTP_OFFSET});
if (DL_FDPIC && sym && sym->st_shndx && (sym->st_info&0xf) == STT_FUNC)
return p->deps[i]->funcdescs + (sym - p->deps[i]->syms);
if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
return laddr(p->deps[i], sym->st_value);
}
failed:
error("Symbol not found: %s", s);
return 0;
if ((def.sym->st_info&0xf) == STT_TLS)
return __tls_get_addr((tls_mod_off_t []){def.dso->tls_id, def.sym->st_value-DTP_OFFSET});
if (DL_FDPIC && (def.sym->st_info&0xf) == STT_FUNC)
return def.dso->funcdescs + (def.sym - def.dso->syms);
return laddr(def.dso, def.sym->st_value);
}
int dladdr(const void *addr_arg, Dl_info *info)