>From b5e20dbf30e67a12bc0931f12126553d036bbd31 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <nsz@port70.net>
Date: Sat, 3 Dec 2016 23:08:44 +0000
Subject: [PATCH 2/2] make relocation time symbol lookup and dlsym consistent
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).
TODO: not benchmarked, common code should be inlined probably.
---
ldso/dynlink.c | 83 +++++++++++++++++++---------------------------------------
1 file changed, 27 insertions(+), 56 deletions(-)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 476cd6a8..e5a382b0 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -256,14 +256,15 @@ 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)
+static struct symdef find_sym(struct dso *dso, const char *s, int need_def, int use_deps)
{
uint32_t h = 0, gh, gho, *ght;
size_t ghm = 0;
struct symdef def = {0};
- for (; dso; dso=dso->next) {
+ struct dso **deps = use_deps ? dso->deps : 0;
+ for (; dso; dso=use_deps ? *deps++ : dso->next) {
Sym *sym;
- if (!dso->global) continue;
+ if (!dso->global && !use_deps) continue;
if ((ght = dso->ghashtab)) {
if (!ghm) {
gh = gnu_hash(s);
@@ -332,7 +333,7 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
ctx = type==REL_COPY ? head->next : head;
def = (sym->st_info&0xf) == STT_SECTION
? (struct symdef){ .dso = dso, .sym = sym }
- : find_sym(ctx, name, type==REL_PLT);
+ : find_sym(ctx, name, type==REL_PLT, 0);
if (!def.sym && (sym->st_shndx != SHN_UNDEF
|| sym->st_info>>4 != STB_WEAK)) {
error("Error relocating %s: %s: symbol not found",
@@ -1377,7 +1378,7 @@ void __dls2(unsigned char *base, size_t *sp)
/* Call dynamic linker stage-3, __dls3, looking it up
* symbolically as a barrier against moving the address
* load across the above relocation processing. */
- struct symdef dls3_def = find_sym(&ldso, "__dls3", 0);
+ struct symdef dls3_def = find_sym(&ldso, "__dls3", 0, 0);
if (DL_FDPIC) ((stage3_func)&ldso.funcdescs[dls3_def.sym-ldso.syms])(sp);
else ((stage3_func)laddr(&ldso, dls3_def.sym->st_value))(sp);
}
@@ -1770,58 +1771,28 @@ void *__tls_get_addr(size_t *);
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((size_t []){def.dso->tls_id, def.sym->st_value});
- 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))
+ struct symdef def;
+ 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;
- 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((size_t []){p->tls_id, sym->st_value});
- 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);
- if (p->deps) 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((size_t []){p->deps[i]->tls_id, sym->st_value});
- 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;
+ } else
+ use_deps = 1;
+ def = find_sym(p, s, 0, use_deps);
+ if (!def.sym) {
+ error("Symbol not found: %s", s);
+ return 0;
+ }
+ if ((def.sym->st_info&0xf) == STT_TLS)
+ return __tls_get_addr((size_t []){def.dso->tls_id, def.sym->st_value});
+ 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, Dl_info *info)
--
2.11.0