LD_PRELOAD support

[musl] / src / ldso / dynlink.c

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index d8f641a..ced1637 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -14,6 +14,7 @@
 #include <elf.h>
 #include <setjmp.h>
 #include <pthread.h>
+#include <ctype.h>
 #include <dlfcn.h>
 
 #include "reloc.h"
@@ -92,10 +93,12 @@ static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char
 }
 
 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
+#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK)
 
 static void *find_sym(struct dso *dso, const char *s, int need_def)
 {
        uint32_t h = hash(s);
+       void *def = 0;
        if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
        if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
        for (; dso; dso=dso->next) {
@@ -103,10 +106,14 @@ 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)
@@ -404,6 +411,20 @@ static void load_deps(struct dso *p)
        }
 }
 
+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;
+       }
+}
+
 static void make_global(struct dso *p)
 {
        for (; p; p=p->next) p->global = 1;
@@ -449,11 +470,14 @@ void *__dynlink(int argc, char **argv, size_t *got)
        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[] */
        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);
@@ -469,6 +493,7 @@ void *__dynlink(int argc, char **argv, size_t *got)
        if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
          || aux[AT_GID]!=aux[AT_EGID]) {
                env_path = 0;
+               env_preload = 0;
        }
 
        /* Relocate ldso's DYNAMIC pointer and load vector */
@@ -519,6 +544,7 @@ void *__dynlink(int argc, char **argv, size_t *got)
                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;
 
                vdso->prev = lib;
                lib->next = vdso;
@@ -540,6 +566,7 @@ void *__dynlink(int argc, char **argv, size_t *got)
        head = tail = app;
        libc = lib;
        app->next = 0;
+       if (env_preload) load_preload(env_preload);
        load_deps(head);
 
        make_global(head);