X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fldso%2Fdynlink.c;h=df54230c8cf2517ce9941f14b711f51297b3fcae;hp=527b36bd12cdc6c01764e7a6cf79e470300d4d2a;hb=e12fe65c928f038fb8db0caddcf535ab0a980c58;hpb=bf30100ad7e208dbac5835b38881c98ceb5b928f diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index 527b36bd..df54230c 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -1,3 +1,4 @@ +#ifdef __PIC__ #include #include #include @@ -14,6 +15,7 @@ #include #include #include +#include #include #include "reloc.h" @@ -53,13 +55,13 @@ struct dso }; static struct dso *head, *tail, *libc; -static char *env_path, *sys_path; +static char *env_path, *sys_path, *r_path; static int rtld_used; static int runtime; static jmp_buf rtld_fail; static pthread_rwlock_t lock; -#define AUX_CNT 15 +#define AUX_CNT 24 #define DYN_CNT 34 static void decode_vec(size_t *v, size_t *a, size_t cnt) @@ -71,8 +73,9 @@ static void decode_vec(size_t *v, size_t *a, size_t cnt) } } -static uint32_t hash(const char *s) +static uint32_t hash(const char *s0) { + const unsigned char *s = (void *)s0; uint_fast32_t h = 0; while (*s) { h = 16*h + *s++; @@ -92,10 +95,12 @@ static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char } #define OK_TYPES (1<next) { @@ -103,10 +108,14 @@ static void *find_sym(struct dso *dso, const char *s, int need_def) if (!dso->global) continue; sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings); if (sym && (!need_def || sym->st_shndx) && sym->st_value - && (1<<(sym->st_info&0xf) & OK_TYPES)) - return dso->base + sym->st_value; + && (1<<(sym->st_info&0xf) & OK_TYPES) + && (1<<(sym->st_info>>4) & OK_BINDS)) { + if (def && sym->st_info>>4 == STB_WEAK) continue; + def = dso->base + sym->st_value; + if (sym->st_info>>4 == STB_GLOBAL) break; + } } - return 0; + return def; } static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso) @@ -139,6 +148,37 @@ static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t } } +/* A huge hack: to make up for the wastefulness of shared libraries + * needing at least a page of dirty memory even if they have no global + * data, we reclaim the gaps at the beginning and end of writable maps + * and "donate" them to the heap by setting up minimal malloc + * structures and then freeing them. */ + +static void reclaim(unsigned char *base, size_t start, size_t end) +{ + size_t *a, *z; + start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t); + end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t); + if (start>end || end-start < 4*sizeof(size_t)) return; + a = (size_t *)(base + start); + z = (size_t *)(base + end); + a[-2] = 1; + a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1; + z[1] = 1; + free(a); +} + +static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt) +{ + for (; phcnt--; ph=(void *)((char *)ph+phent)) { + if (ph->p_type!=PT_LOAD) continue; + if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue; + reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr); + reclaim(base, ph->p_vaddr+ph->p_memsz, + ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE); + } +} + static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp) { Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)]; @@ -217,6 +257,13 @@ static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dy } } } + for (i=0; ((size_t *)(base+dyn))[i]; i+=2) + if (((size_t *)(base+dyn))[i]==DT_TEXTREL) { + mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC); + break; + } + if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff), + eh->e_phentsize, eh->e_phnum); *lenp = map_len; *basep = base; *dynp = dyn; @@ -239,12 +286,20 @@ static int path_open(const char *name, const char *search) } } +static void decode_dyn(struct dso *p) +{ + 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->strings = (void *)(p->base + dyn[DT_STRTAB]); +} + static struct dso *load_library(const char *name) { unsigned char *base, *map; size_t dyno, map_len; struct dso *p; - size_t dyn[DYN_CNT] = {0}; int fd; struct stat st; @@ -260,7 +315,7 @@ static struct dso *load_library(const char *name) if (!libc->prev) { tail->next = libc; libc->prev = tail; - tail = libc; + tail = libc->next ? libc->next : libc; } return libc; } @@ -278,7 +333,8 @@ static struct dso *load_library(const char *name) } else { if (strlen(name) > NAME_MAX) return 0; fd = -1; - if (env_path) fd = path_open(name, env_path); + if (r_path) fd = path_open(name, r_path); + if (fd < 0 && env_path) fd = path_open(name, env_path); if (fd < 0) { if (!sys_path) { FILE *f = fopen(ETC_LDSO_PATH, "r"); @@ -317,11 +373,8 @@ static struct dso *load_library(const char *name) p->map_len = map_len; p->base = base; p->dynv = (void *)(base + dyno); - decode_vec(p->dynv, dyn, DYN_CNT); + decode_dyn(p); - p->syms = (void *)(base + dyn[DT_SYMTAB]); - p->hashtab = (void *)(base + dyn[DT_HASH]); - p->strings = (void *)(base + dyn[DT_STRTAB]); p->dev = st.st_dev; p->ino = st.st_ino; p->refcnt = 1; @@ -340,6 +393,10 @@ static void load_deps(struct dso *p) size_t i, ndeps=0; struct dso ***deps = &p->deps, **tmp, *dep; for (; p; p=p->next) { + for (i=0; p->dynv[i]; i+=2) { + if (p->dynv[i] != DT_RPATH) continue; + r_path = (void *)(p->strings + p->dynv[i+1]); + } for (i=0; p->dynv[i]; i+=2) { if (p->dynv[i] != DT_NEEDED) continue; dep = load_library(p->strings + p->dynv[i+1]); @@ -357,6 +414,21 @@ static void load_deps(struct dso *p) *deps = tmp; } } + r_path = 0; + } +} + +static void load_preload(char *s) +{ + int tmp; + char *z; + for (z=s; *z; s=z) { + for ( ; *s && isspace(*s); s++); + for (z=s; *z && !isspace(*z); z++); + tmp = *z; + *z = 0; + load_library(s); + *z = tmp; } } @@ -391,93 +463,121 @@ static void free_all(struct dso *p) } } -void *__dynlink(int argc, char **argv, size_t *got) +static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride) +{ + for (; cnt--; ph = (void *)((char *)ph + stride)) + if (ph->p_type == PT_DYNAMIC) + return ph->p_vaddr; + return 0; +} + +void *__dynlink(int argc, char **argv) { size_t *auxv, aux[AUX_CNT] = {0}; - size_t app_dyn[DYN_CNT] = {0}; - size_t lib_dyn[DYN_CNT] = {0}; size_t i; Phdr *phdr; - struct dso lib, app; + Ehdr *ehdr; + static struct dso builtin_dsos[3]; + struct dso *const app = builtin_dsos+0; + struct dso *const lib = builtin_dsos+1; + struct dso *const vdso = builtin_dsos+2; + char *env_preload=0; /* Find aux vector just past environ[] */ for (i=argc+1; argv[i]; i++) if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16)) env_path = argv[i]+16; + else if (!memcmp(argv[i], "LD_PRELOAD=", 11)) + env_preload = argv[i]+11; auxv = (void *)(argv+i+1); decode_vec(auxv, aux, AUX_CNT); /* Only trust user/env if kernel says we're not suid/sgid */ if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID] - || aux[AT_GID]!=aux[AT_EGID]) { + || aux[AT_GID]!=aux[AT_EGID] || aux[AT_SECURE]) { env_path = 0; + env_preload = 0; } - /* Relocate ldso's DYNAMIC pointer and load vector */ - decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT); - - /* Find the program image's DYNAMIC section and decode it */ + /* The dynamic linker load address is passed by the kernel + * in the AUX vector, so this is easy. */ + lib->base = (void *)aux[AT_BASE]; + lib->name = "libc.so"; + lib->global = 1; + ehdr = (void *)lib->base; + lib->dynv = (void *)(lib->base + find_dyn( + (void *)(aux[AT_BASE]+ehdr->e_phoff), + ehdr->e_phnum, ehdr->e_phentsize)); + decode_dyn(lib); + + /* Find load address of the main program, via AT_PHDR vs PT_PHDR. */ + app->base = 0; phdr = (void *)aux[AT_PHDR]; - for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) { - if (phdr->p_type == PT_DYNAMIC) { - decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT); - break; + for (i=aux[AT_PHNUM]; i; i--, phdr=(void *)((char *)phdr + aux[AT_PHENT])) { + if (phdr->p_type == PT_PHDR) + app->base = (void *)(aux[AT_PHDR] - phdr->p_vaddr); + } + app->name = argv[0]; + app->global = 1; + app->dynv = (void *)(app->base + find_dyn( + (void *)aux[AT_PHDR], aux[AT_PHNUM], aux[AT_PHENT])); + decode_dyn(app); + + /* Attach to vdso, if provided by the kernel */ + for (i=0; auxv[i]; i+=2) { + size_t vdso_base = auxv[i+1]; + if (auxv[i] != AT_SYSINFO_EHDR) continue; + ehdr = (void *)vdso_base; + phdr = (void *)(vdso_base + ehdr->e_phoff); + for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) { + if (phdr->p_type == PT_DYNAMIC) + vdso->dynv = (void *)(vdso_base + phdr->p_offset); + if (phdr->p_type == PT_LOAD) + vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset); } + vdso->name = "linux-gate.so.1"; + vdso->global = 1; + decode_dyn(vdso); + vdso->prev = lib; + lib->next = vdso; + break; } - app = (struct dso){ - .base = 0, - .strings = (void *)(app_dyn[DT_STRTAB]), - .hashtab = (void *)(app_dyn[DT_HASH]), - .syms = (void *)(app_dyn[DT_SYMTAB]), - .dynv = (void *)(phdr->p_vaddr), - .name = argv[0], - .global = 1, - .next = &lib - }; - - lib = (struct dso){ - .base = (void *)aux[AT_BASE], - .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]), - .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]), - .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]), - .dynv = (void *)(got[0]), - .name = "libc.so", - .global = 1, - .relocated = 1 - }; - - /* Relocate the dynamic linker/libc */ - do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]), - lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app); - do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]), - lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app); - - /* At this point the standard library is fully functional */ - - head = tail = &app; - libc = &lib; - app.next = 0; - load_deps(head); - - make_global(head); - reloc_all(head->next); - reloc_all(head); - - if (rtld_used) { - runtime = 1; - head->next->prev = malloc(sizeof *head); - *head->next->prev = *head; - head = head->next->prev; - libc->prev->next = malloc(sizeof *libc); - *libc->prev->next = *libc; - libc = libc->prev->next; - if (libc->next) libc->next->prev = libc; - if (tail == &lib) tail = libc; - } else { + /* Initial dso chain consists only of the app. We temporarily + * append the dynamic linker/libc so we can relocate it, then + * restore the initial chain in preparation for loading third + * party libraries (preload/needed). */ + head = tail = app; + libc = lib; + app->next = lib; + reloc_all(lib); + app->next = 0; + + /* PAST THIS POINT, ALL LIBC INTERFACES ARE FULLY USABLE. */ + + /* Donate unused parts of app and library mapping to malloc */ + reclaim_gaps(app->base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]); + ehdr = (void *)lib->base; + reclaim_gaps(lib->base, (void *)(lib->base+ehdr->e_phoff), + ehdr->e_phentsize, ehdr->e_phnum); + + /* Load preload/needed libraries, add their symbols to the global + * namespace, and perform all remaining relocations. */ + if (env_preload) load_preload(env_preload); + load_deps(app); + make_global(app); + reloc_all(app); + + /* Switch to runtime mode: any further failures in the dynamic + * linker are a reportable failure rather than a fatal startup + * error. If the dynamic loader (dlopen) will not be used, free + * all memory used by the dynamic linker. */ + runtime = 1; + if (!rtld_used) { free_all(head); free(sys_path); + reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos); } errno = 0; @@ -486,7 +586,7 @@ void *__dynlink(int argc, char **argv, size_t *got) void *dlopen(const char *file, int mode) { - struct dso *p, *orig_tail = tail, *next; + struct dso *volatile p, *orig_tail = tail, *next; size_t i; if (!file) return head; @@ -538,11 +638,16 @@ end: return p; } -static void *do_dlsym(struct dso *p, const char *s) +static void *do_dlsym(struct dso *p, const char *s, void *ra) { size_t i; uint32_t h; Sym *sym; + if (p == RTLD_NEXT) { + for (p=head; p && (unsigned char *)ra-p->map>p->map_len; p=p->next); + if (!p) p=head; + p=p->next; + } if (p == head || p == RTLD_DEFAULT) return find_sym(head, s, 0); h = hash(s); @@ -558,11 +663,11 @@ static void *do_dlsym(struct dso *p, const char *s) return 0; } -void *dlsym(void *p, const char *s) +void *__dlsym(void *p, const char *s, void *ra) { void *res; pthread_rwlock_rdlock(&lock); - res = do_dlsym(p, s); + res = do_dlsym(p, s, ra); pthread_rwlock_unlock(&lock); return res; } @@ -576,3 +681,4 @@ int dlclose(void *p) { return 0; } +#endif