>From a57cd35acf26ba6202ed6534a57f496464f431a1 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Sat, 10 Aug 2019 23:14:40 +0000 Subject: [PATCH] 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) 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. --- ldso/dynlink.c | 84 +++++++++++++++++++------------------------------- 1 file changed, 31 insertions(+), 53 deletions(-) diff --git a/ldso/dynlink.c b/ldso/dynlink.c index d1edb131..07871869 100644 --- a/ldso/dynlink.c +++ b/ldso/dynlink.c @@ -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; @@ -2118,58 +2127,27 @@ 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; - 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; + } 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 ((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) -- 2.21.0