dladdr support for dynamic linker (nonstandard extension)

[musl] / src / ldso / dynlink.c

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 6ffda49..b8c26ac 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -584,6 +585,22 @@ static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride)
        return 0;
 }
 
+static void find_map_range(Phdr *ph, size_t cnt, size_t stride, struct dso *p)
+{
+       size_t min_addr = -1, max_addr = 0;
+       for (; cnt--; ph = (void *)((char *)ph + stride)) {
+               if (ph->p_type != PT_LOAD) continue;
+               if (ph->p_vaddr < min_addr)
+                       min_addr = ph->p_vaddr;
+               if (ph->p_vaddr+ph->p_memsz > max_addr)
+                       max_addr = ph->p_vaddr+ph->p_memsz;
+       }
+       min_addr &= -PAGE_SIZE;
+       max_addr = (max_addr + PAGE_SIZE-1) & -PAGE_SIZE;
+       p->map = p->base + min_addr;
+       p->map_len = max_addr - min_addr;
+}
+
 static void do_init_fini(struct dso *p)
 {
        size_t dyn[DYN_CNT] = {0};
@@ -613,6 +630,7 @@ void *__dynlink(int argc, char **argv)
        struct dso *const lib = builtin_dsos+1;
        struct dso *const vdso = builtin_dsos+2;
        char *env_preload=0;
+       size_t vdso_base;
 
        /* Find aux vector just past environ[] */
        for (i=argc+1; argv[i]; i++)
@@ -646,6 +664,8 @@ void *__dynlink(int argc, char **argv)
        lib->name = lib->shortname = "libc.so";
        lib->global = 1;
        ehdr = (void *)lib->base;
+       find_map_range((void *)(aux[AT_BASE]+ehdr->e_phoff),
+               ehdr->e_phnum, ehdr->e_phentsize, lib);
        lib->dynv = (void *)(lib->base + find_dyn(
                (void *)(aux[AT_BASE]+ehdr->e_phoff),
                ehdr->e_phnum, ehdr->e_phentsize));
@@ -665,6 +685,8 @@ void *__dynlink(int argc, char **argv)
                app->name = argv[0];
                app->dynv = (void *)(app->base + find_dyn(
                        (void *)aux[AT_PHDR], aux[AT_PHNUM], aux[AT_PHENT]));
+               find_map_range((void *)aux[AT_PHDR],
+                       aux[AT_PHNUM], aux[AT_PHENT], app);
        } else {
                int fd;
                char *ldname = argv[0];
@@ -701,9 +723,7 @@ void *__dynlink(int argc, char **argv)
        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;
+       if (search_vec(auxv, &vdso_base, AT_SYSINFO_EHDR)) {
                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)) {
@@ -717,7 +737,6 @@ void *__dynlink(int argc, char **argv)
                decode_dyn(vdso);
                vdso->prev = lib;
                lib->next = vdso;
-               break;
        }
 
        /* Initial dso chain consists only of the app. We temporarily
@@ -879,7 +898,7 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)
        if (p->deps) for (i=0; p->deps[i]; i++) {
                if (p->deps[i]->ghashtab) {
                        if (!gh) gh = gnu_hash(s);
-                       sym = gnu_lookup(s, h, p->deps[i]);
+                       sym = gnu_lookup(s, gh, p->deps[i]);
                } else {
                        if (!h) h = sysv_hash(s);
                        sym = sysv_lookup(s, h, p->deps[i]);
@@ -893,6 +912,67 @@ failed:
        return 0;
 }
 
+int __dladdr(void *addr, Dl_info *info)
+{
+       struct dso *p;
+       Sym *sym;
+       uint32_t nsym;
+       char *strings;
+       size_t i;
+       void *best = 0;
+       char *bestname;
+
+       pthread_rwlock_rdlock(&lock);
+       for (p=head; p && (unsigned char *)addr-p->map>p->map_len; p=p->next);
+       pthread_rwlock_unlock(&lock);
+
+       if (!p) return 0;
+
+       sym = p->syms;
+       strings = p->strings;
+       if (p->hashtab) {
+               nsym = p->hashtab[1];
+       } else {
+               uint32_t *buckets;
+               uint32_t *hashval;
+               buckets = p->ghashtab + 4 + (p->ghashtab[2]*sizeof(size_t)/4);
+               sym += p->ghashtab[1];
+               for (i = 0; i < p->ghashtab[0]; i++) {
+                       if (buckets[i] > nsym)
+                               nsym = buckets[i];
+               }
+               if (nsym) {
+                       nsym -= p->ghashtab[1];
+                       hashval = buckets + p->ghashtab[0] + nsym;
+                       do nsym++;
+                       while (!(*hashval++ & 1));
+               }
+       }
+
+       for (; nsym; nsym--, sym++) {
+               if (sym->st_shndx && sym->st_value
+                && (1<<(sym->st_info&0xf) & OK_TYPES)
+                && (1<<(sym->st_info>>4) & OK_BINDS)) {
+                       void *symaddr = p->base + sym->st_value;
+                       if (symaddr > addr || symaddr < best)
+                               continue;
+                       best = symaddr;
+                       bestname = strings + sym->st_name;
+                       if (addr == symaddr)
+                               break;
+               }
+       }
+
+       if (!best) return 0;
+
+       info->dli_fname = p->name;
+       info->dli_fbase = p->base;
+       info->dli_sname = bestname;
+       info->dli_saddr = best;
+
+       return 1;
+}
+
 void *__dlsym(void *p, const char *s, void *ra)
 {
        void *res;
@@ -910,6 +990,10 @@ void *__dlsym(void *p, const char *s, void *ra)
 {
        return 0;
 }
+int __dladdr (void *addr, Dl_info *info)
+{
+       return 0;
+}
 #endif
 
 char *dlerror()