Merge changes I3bd27087,I0c9ec550,I3a0e5e86 into eclair

* changes:
  bionic/linker: allow resolving of symbols from library back to executable
  bionic/linker: change lookup() to return soinfo, not base
  Revert "Revert "bionic/linker: fix symbol lookup during relocations""

3 files changed, 107 insertions, 34 deletions

diff --git a/linker/dlfcn.c b/linker/dlfcn.c
index b54674f..053713c 100644
--- a/linker/dlfcn.c
+++ b/linker/dlfcn.c
@@ -74,7 +74,7 @@ const char *dlerror(void)
 
 void *dlsym(void *handle, const char *symbol)
 {
-    unsigned base;
+    soinfo *found;
     Elf32_Sym *sym;
     unsigned bind;
 
@@ -90,19 +90,19 @@ void *dlsym(void *handle, const char *symbol)
     }
 
     if(handle == RTLD_DEFAULT) {
-        sym = lookup(symbol, &base);
+        sym = lookup(symbol, &found);
     } else if(handle == RTLD_NEXT) {
-        sym = lookup(symbol, &base);
+        sym = lookup(symbol, &found);
     } else {
-        sym = lookup_in_library((soinfo*) handle, symbol);
-        base = ((soinfo*) handle)->base;
+        found = (soinfo*)handle;
+        sym = lookup_in_library(found, symbol);
     }
 
     if(likely(sym != 0)) {
         bind = ELF32_ST_BIND(sym->st_info);
 
         if(likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) {
-            unsigned ret = sym->st_value + base;
+            unsigned ret = sym->st_value + found->base;
             pthread_mutex_unlock(&dl_lock);
             return (void*)ret;
         }
diff --git a/linker/linker.c b/linker/linker.c
index eed9738..26cd0a8 100644
--- a/linker/linker.c
+++ b/linker/linker.c
@@ -51,6 +51,7 @@
 
 #include "ba.h"
 
+#define ALLOW_SYMBOLS_FROM_MAIN 1
 #define SO_MAX 96
 
 /* Assume average path length of 64 and max 8 paths */
@@ -86,6 +87,15 @@ static soinfo sopool[SO_MAX];
 static soinfo *freelist = NULL;
 static soinfo *solist = &libdl_info;
 static soinfo *sonext = &libdl_info;
+#if ALLOW_SYMBOLS_FROM_MAIN
+static soinfo *somain; /* main process, always the one after libdl_info */
+#endif
+
+static inline int validate_soinfo(soinfo *si)
+{
+    return (si >= sopool && si < sopool + SO_MAX) ||
+        si == &libdl_info;
+}
 
 static char ldpaths_buf[LDPATH_BUFSIZE];
 static const char *ldpaths[LDPATH_MAX + 1];
@@ -421,41 +431,92 @@ _do_lookup_in_so(soinfo *si, const char *name, unsigned *elf_hash)
     return _elf_lookup (si, *elf_hash, name);
 }
 
-/* This is used by dl_sym() */
+static Elf32_Sym *
+_do_lookup(soinfo *si, const char *name, unsigned *base)
+{
+    unsigned elf_hash = 0;
+    Elf32_Sym *s;
+    unsigned *d;
+    soinfo *lsi = si;
+
+    /* Look for symbols in the local scope first (the object who is
+     * searching). This happens with C++ templates on i386 for some
+     * reason. */
+    s = _do_lookup_in_so(si, name, &elf_hash);
+    if(s != NULL)
+        goto done;
+
+    for(d = si->dynamic; *d; d += 2) {
+        if(d[0] == DT_NEEDED){
+            lsi = (soinfo *)d[1];
+            if (!validate_soinfo(lsi)) {
+                DL_ERR("%5d bad DT_NEEDED pointer in %s",
+                       pid, si->name);
+                return 0;
+            }
+
+            DEBUG("%5d %s: looking up %s in %s\n",
+                  pid, si->name, name, lsi->name);
+            s = _do_lookup_in_so(lsi, name, &elf_hash);
+            if(s != NULL)
+                goto done;
+        }
+    }
+
+#if ALLOW_SYMBOLS_FROM_MAIN
+    /* If we are resolving relocations while dlopen()ing a library, it's OK for
+     * the library to resolve a symbol that's defined in the executable itself,
+     * although this is rare and is generally a bad idea.
+     */
+    if (somain) {
+        lsi = somain;
+        DEBUG("%5d %s: looking up %s in executable %s\n",
+              pid, si->name, name, lsi->name);
+        s = _do_lookup_in_so(lsi, name, &elf_hash);
+    }
+#endif
+
+done:
+    if(s != NULL) {
+        TRACE_TYPE(LOOKUP, "%5d si %s sym %s s->st_value = 0x%08x, "
+                   "found in %s, base = 0x%08x\n",
+                   pid, si->name, name, s->st_value, lsi->name, lsi->base);
+        *base = lsi->base;
+        return s;
+    }
+
+    return 0;
+}
+
+/* This is used by dl_sym().  It performs symbol lookup only within the
+   specified soinfo object and not in any of its dependencies.
+ */
 Elf32_Sym *lookup_in_library(soinfo *si, const char *name)
 {
     unsigned unused = 0;
     return _do_lookup_in_so(si, name, &unused);
 }
 
-static Elf32_Sym *
-_do_lookup(soinfo *user_si, const char *name, unsigned *base)
+/* This is used by dl_sym().  It performs a global symbol lookup.
+ */
+Elf32_Sym *lookup(const char *name, soinfo **found)
 {
     unsigned elf_hash = 0;
     Elf32_Sym *s = NULL;
     soinfo *si;
 
-    /* Look for symbols in the local scope first (the object who is
-     * searching). This happens with C++ templates on i386 for some
-     * reason. */
-    if (user_si) {
-        s = _do_lookup_in_so(user_si, name, &elf_hash);
-        if (s != NULL)
-            *base = user_si->base;
-    }
-
     for(si = solist; (s == NULL) && (si != NULL); si = si->next)
     {
-        if((si->flags & FLAG_ERROR) || (si == user_si))
+        if(si->flags & FLAG_ERROR)
             continue;
         s = _do_lookup_in_so(si, name, &elf_hash);
         if (s != NULL) {
-            *base = si->base;
+            *found = si;
             break;
         }
     }
 
-    if (s != NULL) {
+    if(s != NULL) {
         TRACE_TYPE(LOOKUP, "%5d %s s->st_value = 0x%08x, "
                    "si->base = 0x%08x\n", pid, name, s->st_value, si->base);
         return s;
@@ -464,12 +525,6 @@ _do_lookup(soinfo *user_si, const char *name, unsigned *base)
     return 0;
 }
 
-/* This is used by dl_sym() */
-Elf32_Sym *lookup(const char *name, unsigned *base)
-{
-    return _do_lookup(NULL, name, base);
-}
-
 #if 0
 static void dump(soinfo *si)
 {
@@ -1116,14 +1171,16 @@ unsigned unload_library(soinfo *si)
 
         for(d = si->dynamic; *d; d += 2) {
             if(d[0] == DT_NEEDED){
-                TRACE("%5d %s needs to unload %s\n", pid,
-                      si->name, si->strtab + d[1]);
-                soinfo *lsi = find_library(si->strtab + d[1]);
-                if(lsi)
+                soinfo *lsi = (soinfo *)d[1];
+                d[1] = 0;
+                if (validate_soinfo(lsi)) {
+                    TRACE("%5d %s needs to unload %s\n", pid,
+                          si->name, lsi->name);
                     unload_library(lsi);
+                }
                 else
-                    DL_ERR("%5d could not unload '%s'",
-                          pid, si->strtab + d[1]);
+                    DL_ERR("%5d %s: could not unload dependent library",
+                           pid, si->name);
             }
         }
 
@@ -1641,6 +1698,14 @@ static int link_image(soinfo *si, unsigned wr_offset)
                        pid, si->strtab + d[1], si->name, tmp_err_buf);
                 goto fail;
             }
+            /* Save the soinfo of the loaded DT_NEEDED library in the payload
+               of the DT_NEEDED entry itself, so that we can retrieve the
+               soinfo directly later from the dynamic segment.  This is a hack,
+               but it allows us to map from DT_NEEDED to soinfo efficiently
+               later on when we resolve relocations, trying to look up a symgol
+               with dlsym().
+            */
+            d[1] = (unsigned)lsi;
             lsi->refcount++;
         }
     }
@@ -1846,6 +1911,14 @@ unsigned __linker_init(unsigned **elfdata)
         exit(-1);
     }
 
+#if ALLOW_SYMBOLS_FROM_MAIN
+    /* Set somain after we've loaded all the libraries in order to prevent
+     * linking of symbols back to the main image, which is not set up at that
+     * point yet.
+     */
+    somain = si;
+#endif
+
 #if TIMING
     gettimeofday(&t1,NULL);
     PRINT("LINKER TIME: %s: %d microseconds\n", argv[0], (int) (
diff --git a/linker/linker.h b/linker/linker.h
index 69042c0..d289c81 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -203,7 +203,7 @@ extern soinfo libdl_info;
 soinfo *find_library(const char *name);
 unsigned unload_library(soinfo *si);
 Elf32_Sym *lookup_in_library(soinfo *si, const char *name);
-Elf32_Sym *lookup(const char *name, unsigned *base);
+Elf32_Sym *lookup(const char *name, soinfo **found);
 const char *linker_get_error(void);
 
 #ifdef ANDROID_ARM_LINKER