diff options
| -rw-r--r-- | src/ldso/dynlink.c | 146 |
1 files changed, 66 insertions, 80 deletions
diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index b26992d3..e1c2ad7d 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -286,12 +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; @@ -365,11 +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; @@ -458,21 +463,24 @@ 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 vdso_dyn[DYN_CNT] = {0}; size_t i; Phdr *phdr; Ehdr *ehdr; - size_t *lib_dynv; 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; - size_t vdso_base=0; char *env_preload=0; /* Find aux vector just past environ[] */ @@ -492,56 +500,31 @@ void *__dynlink(int argc, char **argv, size_t *got) env_preload = 0; } + /* 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); + + /* Assume base address of 0 for the main program. This is not + * valid for PIE code; we will have to search the PHDR to get + * the correct load address in the PIE case (not yet supported). */ + app->base = 0; + 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) { - if (auxv[i]==AT_SYSINFO_EHDR) { - vdso_base = auxv[i+1]; - break; - } - } - - /* Find the dynamic linker's DYNAMIC section and decode it */ - ehdr = (void *)aux[AT_BASE]; - phdr = (void *)(aux[AT_BASE] + ehdr->e_phoff); - for (i=ehdr->e_phnum; i--; phdr=(void *)((char *)phdr + ehdr->e_phentsize)) { - if (phdr->p_type == PT_DYNAMIC) { - lib_dynv = (void *)(aux[AT_BASE] + phdr->p_vaddr); - decode_vec(lib_dynv, lib_dyn, DYN_CNT); - break; - } - } - - /* Find the program image's DYNAMIC section and decode it */ - 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; - } - } - - *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 = lib_dynv, - .name = "libc.so", - .global = 1, - .relocated = 1 - }; - - if (vdso_base) { + 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)) { @@ -550,40 +533,43 @@ void *__dynlink(int argc, char **argv, size_t *got) if (phdr->p_type == PT_LOAD) vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset); } - decode_vec(vdso->dynv, vdso_dyn, DYN_CNT); - vdso->syms = (void *)(vdso->base + vdso_dyn[DT_SYMTAB]); - vdso->hashtab = (void *)(vdso->base + vdso_dyn[DT_HASH]); - vdso->strings = (void *)(vdso->base + vdso_dyn[DT_STRTAB]); vdso->name = "linux-gate.so.1"; vdso->global = 1; - + decode_dyn(vdso); vdso->prev = lib; lib->next = vdso; + break; } - /* 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); + /* 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; - /* At this point the standard library is fully functional */ + /* 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); - head = tail = app; - libc = lib; - app->next = 0; + /* 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(head); - - make_global(head); - reloc_all(head->next); - reloc_all(head); - + 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); |