>From 4a809b89c38ca3a5b69e5758a04effd6d404039c Mon Sep 17 00:00:00 2001 From: Boris BREZILLON Date: Wed, 8 Aug 2012 11:45:31 +0200 Subject: [PATCH] ldso : add dladdr and gnu hash support --- include/dlfcn.h | 15 ++++ src/ldso/dynlink.c | 231 +++++++++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 235 insertions(+), 11 deletions(-) diff --git a/include/dlfcn.h b/include/dlfcn.h index dea74c7..8c45822 100644 --- a/include/dlfcn.h +++ b/include/dlfcn.h @@ -18,6 +18,21 @@ char *dlerror(void); void *dlopen(const char *, int); void *dlsym(void *, const char *); +#ifdef _GNU_SOURCE +typedef struct { + const char *dli_fname; /* Pathname of shared object that + contains address */ + void *dli_fbase; /* Address at which shared object + is loaded */ + const char *dli_sname; /* Name of nearest symbol with address + lower than addr */ + void *dli_saddr; /* Exact address of symbol named + in dli_sname */ +} Dl_info; + +int dladdr (void *addr, Dl_info *info); +#endif + #ifdef __cplusplus } #endif diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index f55c6f1..f40c1e5 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -1,3 +1,4 @@ +#define _GNU_SOURCE #include #include #include @@ -28,12 +29,14 @@ typedef Elf32_Phdr Phdr; typedef Elf32_Sym Sym; #define R_TYPE(x) ((x)&255) #define R_SYM(x) ((x)>>8) +#define ELF_ST_TYPE ELF32_ST_TYPE #else typedef Elf64_Ehdr Ehdr; typedef Elf64_Phdr Phdr; typedef Elf64_Sym Sym; #define R_TYPE(x) ((x)&0xffffffff) #define R_SYM(x) ((x)>>32) +#define ELF_ST_TYPE ELF64_ST_TYPE #endif struct debug { @@ -52,6 +55,7 @@ struct dso { int refcnt; Sym *syms; + uint32_t hashalg; uint32_t *hashtab; char *strings; unsigned char *map; @@ -66,6 +70,10 @@ struct dso { char buf[]; }; +#define SYSV_HASH_ALG_IDX 0 +#define GNU_HASH_ALG_IDX 1 +#define HASH_ALG_CNT 2 + #include "reloc.h" void __init_ssp(size_t *); @@ -94,7 +102,7 @@ static void decode_vec(size_t *v, size_t *a, size_t cnt) } } -static uint32_t hash(const char *s0) +static uint32_t sysv_hash(const char *s0) { const unsigned char *s = (void *)s0; uint_fast32_t h = 0; @@ -105,7 +113,16 @@ static uint32_t hash(const char *s0) return h & 0xfffffff; } -static Sym *lookup(const char *s, uint32_t h, struct dso *dso) +static uint32_t gnu_hash (const char *s0) +{ + const unsigned char *s = (void *)s0; + uint_fast32_t h = 5381; + for (; *s; s++) + h = h*33 + *s; + return h & 0xffffffff; +} + +static Sym *sysv_lookup(const char *s, uint32_t h, struct dso *dso) { size_t i; Sym *syms = dso->syms; @@ -118,20 +135,94 @@ static Sym *lookup(const char *s, uint32_t h, struct dso *dso) return 0; } +static Sym *gnu_lookup(const char *s, uint32_t h1, struct dso *dso) +{ + size_t i; + Sym *sym; + char *strings = dso->strings; + uint32_t *hashtab = dso->hashtab; + uint32_t nbuckets = hashtab[0]; + size_t *maskwords = (size_t *)(hashtab + 4); + uint32_t *buckets = hashtab + 4 + (hashtab[2]*(sizeof(size_t)/sizeof(uint32_t))); + uint32_t symndx = hashtab[1]; + Sym *syms = dso->syms; + uint32_t shift2 = hashtab[3]; + uint32_t h2 = h1 >> shift2; + uint32_t *hashvals = buckets + nbuckets; + uint32_t *hashval; + size_t c = sizeof(size_t) * 8; + size_t n = (h1/c) & (hashtab[2]-1); + size_t bitmask = (1 << (h1%c)) | (1 << (h2%c)); + + if ((maskwords[n] & bitmask) != bitmask) + return 0; + + n = buckets[h1 % nbuckets]; + if (!n) + return 0; + + sym = syms + n; + hashval = hashvals + n - symndx; + + for (h1 &= (uint32_t)-2;; sym++) { + h2 = *hashval++; + if ((h1 == (h2 & ~1)) && !strcmp(s, strings + sym->st_name)) + return sym; + + if (h2 & 1) + break; + } + + return 0; +} + #define OK_TYPES (1<hashalg; + if (alg == SYSV_HASH_ALG_IDX) + h[alg] = sysv_hash(s); + else + h[alg] = gnu_hash(s); + + computed[alg] = 1; + + if (h[alg] == precomp[alg][0] && !strcmp(s, "dlopen")) rtld_used = 1; + if (h[alg] == precomp[alg][1] && !strcmp(s, "dlsym")) rtld_used = 1; + if (h[alg] == precomp[alg][2] && !strcmp(s, "__stack_chk_fail")) ssp_used = 1; + for (; dso; dso=dso->next) { Sym *sym; + if (!dso->global) continue; - sym = lookup(s, h, dso); + + alg = dso->hashalg; + if (!computed[alg]) { + if (alg == SYSV_HASH_ALG_IDX) { + h[alg] = sysv_hash(s); + sym = sysv_lookup(s, h[alg], dso); + } + else { + h[alg] = gnu_hash(s); + sym = gnu_lookup(s, h[alg], dso); + } + computed[alg] = 1; + } else { + if (alg == SYSV_HASH_ALG_IDX) + sym = sysv_lookup(s, h[alg], dso); + else + sym = gnu_lookup(s, h[alg], dso); + } + if (sym && (!need_def || sym->st_shndx) && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES) && (1<<(sym->st_info>>4) & OK_BINDS)) { @@ -320,11 +411,17 @@ static int path_open(const char *name, const char *search, char *buf, size_t buf static void decode_dyn(struct dso *p) { + size_t *v = p->dynv; size_t dyn[DYN_CNT] = {0}; decode_vec(p->dynv, dyn, DYN_CNT); p->syms = (void *)(p->base + dyn[DT_SYMTAB]); p->hashtab = (void *)(p->base + dyn[DT_HASH]); + p->hashalg = SYSV_HASH_ALG_IDX; p->strings = (void *)(p->base + dyn[DT_STRTAB]); + for (; v[0]; v+=2) if (v[0] == DT_GNU_HASH) { + p->hashtab = (void *)(p->base + v[1]); + p->hashalg = GNU_HASH_ALG_IDX; + } } static struct dso *load_library(const char *name) @@ -784,8 +881,11 @@ end: static void *do_dlsym(struct dso *p, const char *s, void *ra) { size_t i; - uint32_t h; Sym *sym; + uint8_t computed[HASH_ALG_CNT] = {0, 0}; + uint8_t alg = p->hashalg; + uint32_t h[HASH_ALG_CNT]; + if (p == RTLD_NEXT) { for (p=head; p && (unsigned char *)ra-p->map>p->map_len; p=p->next); if (!p) p=head; @@ -798,12 +898,36 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra) if (!res) goto failed; return res; } - h = hash(s); - sym = lookup(s, h, p); + + if (alg == SYSV_HASH_ALG_IDX) { + h[alg] = sysv_hash(s); + sym = sysv_lookup(s, h[alg], p); + } else { + h[alg] = gnu_hash(s); + sym = gnu_lookup(s, h[alg], p); + } + computed[alg] = 1; + if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES)) return p->base + sym->st_value; if (p->deps) for (i=0; p->deps[i]; i++) { - sym = lookup(s, h, p->deps[i]); + alg = p->deps[i]->hashalg; + if (!computed[alg]) { + if (alg == SYSV_HASH_ALG_IDX) { + h[alg] = sysv_hash(s); + sym = sysv_lookup(s, h[alg], p->deps[i]); + } else { + h[alg] = gnu_hash(s); + sym = gnu_lookup(s, h[alg], p->deps[i]); + } + computed[alg] = 1; + } else { + if (alg == SYSV_HASH_ALG_IDX) + sym = sysv_lookup(s, h[alg], p->deps[i]); + else + sym = gnu_lookup(s, h[alg], p->deps[i]); + } + if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES)) return p->deps[i]->base + sym->st_value; } @@ -813,6 +937,91 @@ failed: return 0; } +struct sym_search { + void *addr; + Dl_info *info; +}; + +static int find_closest_sym (struct dso *dso, Sym *sym, struct sym_search *search) +{ + void *symaddr = dso->base + sym->st_value; + char *strings = dso->strings; + Dl_info *info = search->info; + void *addr = search->addr; + void *prevaddr = info->dli_saddr; + + if (sym->st_value == 0 && sym->st_shndx == SHN_UNDEF) + return 1; + + if (ELF_ST_TYPE(sym->st_info) == STT_TLS) + return 1; + + if (addr < symaddr) + return 1; + + if (prevaddr && (addr - symaddr) > (addr - prevaddr)) + return 1; + + info->dli_saddr = symaddr; + info->dli_sname = strings + sym->st_name; + + if (addr == symaddr) + return 0; + + return 1; + +} + +static int do_dladdr (void *addr, Dl_info *info) +{ + struct sym_search search; + struct dso *p; + memset (info, 0, sizeof (*info)); + search.info = info; + search.addr = addr; + for (p=head; p; p=p->next) { + if ((unsigned char *)addr >= p->map && (unsigned char *)addr < p->map + p->map_len) { + Sym *syms = p->syms; + uint32_t *hashtab = p->hashtab; + size_t i; + info->dli_fname = p->name; + info->dli_fbase = p->base; + if (p->hashalg == SYSV_HASH_ALG_IDX) { + for (i = 0; i < hashtab[1]; i++) { + if (!find_closest_sym (p, syms + i, &search)) + return 1; + } + } else { + uint32_t *buckets = hashtab + 4 + (hashtab[2] * (sizeof(size_t)/sizeof(uint32_t))); + uint32_t nbuckets = hashtab[0]; + uint32_t *hashvals = buckets + nbuckets; + uint32_t symndx = hashtab[1]; + for (i = 0; i < nbuckets; ++i) { + uint32_t n = buckets[i]; + Sym *sym = syms + n; + uint32_t *hashval = hashvals + n - symndx; + + do { + if (!find_closest_sym (p, sym, &search)) + return 1; + }while (!(*hashval++ & 1)); + } + } + return 1; + } + } + return 0; +} + +int dladdr (void *addr, Dl_info *info) +{ + int res; + pthread_rwlock_rdlock(&lock); + res = do_dladdr (addr, info); + pthread_rwlock_unlock(&lock); + return res; +} + void *__dlsym(void *p, const char *s, void *ra) { void *res; -- 1.7.9.5