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cleanup dynamic linker, removing some code duplication

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This commit is contained in:
Rich Felker 2012-01-23 00:57:38 -05:00
parent 35620515a8
commit c82f4a32ec
1 changed files with 65 additions and 79 deletions
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144
src/ldso/dynlink.c
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@ -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);