More dynamic linker cleanup.

I still want to break linker_format out into its own library so we can reuse
it for malloc debugging and so forth. (There are many similar pieces of code
in bionic, but the linker's one seems to be the most complete/functional.)

Change-Id: If3721853d28937c8e821ca1d23cf200e228a409a

1 files changed, 23 insertions, 50 deletions

diff --git a/linker/linker.cpp b/linker/linker.cpp
index 4ffa1e7..4c52f3d 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -93,7 +93,6 @@ static soinfo *sonext = &libdl_info;
 static soinfo *somain; /* main process, always the one after libdl_info */
 #endif
 
-
 static char ldpaths_buf[LDPATH_BUFSIZE];
 static const char *ldpaths[LDPATH_MAX + 1];
 
@@ -108,9 +107,6 @@ int debug_verbosity;
 
 static int pid;
 
-/* This boolean is set if the program being loaded is setuid */
-static bool program_is_setuid;
-
 enum RelocationKind {
     kRelocAbsolute = 0,
     kRelocRelative,
@@ -257,8 +253,7 @@ static void notify_gdb_of_unload(soinfo* info) {
     rtld_db_dlactivity();
 }
 
-extern "C" void notify_gdb_of_libraries()
-{
+void notify_gdb_of_libraries() {
     _r_debug.r_state = RT_ADD;
     rtld_db_dlactivity();
     _r_debug.r_state = RT_CONSISTENT;
@@ -1689,7 +1684,7 @@ static int soinfo_link_image(soinfo *si)
     ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
 
      */
-    if (program_is_setuid) {
+    if (get_AT_SECURE()) {
         nullify_closed_stdio();
     }
     notify_gdb_of_load(si);
@@ -1750,11 +1745,6 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
     int argc = (int) *elfdata;
     char **argv = (char**) (elfdata + 1);
     unsigned *vecs = (unsigned*) (argv + argc + 1);
-    unsigned *v;
-    soinfo *si;
-    int i;
-    const char *ldpath_env = NULL;
-    const char *ldpreload_env = NULL;
 
     /* NOTE: we store the elfdata pointer on a special location
      *       of the temporary TLS area in order to pass it to
@@ -1773,53 +1763,36 @@ static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linke
     gettimeofday(&t0, 0);
 #endif
 
-    /* Initialize environment functions, and get to the ELF aux vectors table */
+    // Initialize environment functions, and get to the ELF aux vectors table.
     vecs = linker_env_init(vecs);
 
-    /* Check auxv for AT_SECURE first to see if program is setuid, setgid,
-       has file caps, or caused a SELinux/AppArmor domain transition. */
-    for (v = vecs; v[0]; v += 2) {
-        if (v[0] == AT_SECURE) {
-            /* kernel told us whether to enable secure mode */
-            program_is_setuid = v[1];
-            goto sanitize;
-        }
-    }
-
-    /* Kernel did not provide AT_SECURE - fall back on legacy test. */
-    program_is_setuid = (getuid() != geteuid()) || (getgid() != getegid());
-
-sanitize:
-    /* Sanitize environment if we're loading a setuid program */
-    if (program_is_setuid) {
-        linker_env_secure();
-    }
-
     debugger_init();
 
-    /* Get a few environment variables */
-    {
+    // Get a few environment variables.
 #if LINKER_DEBUG
-        const char* env;
-        env = linker_env_get("DEBUG"); /* XXX: TODO: Change to LD_DEBUG */
-        if (env)
+    {
+        const char* env = linker_env_get("LD_DEBUG");
+        if (env != NULL) {
             debug_verbosity = atoi(env);
+        }
+    }
 #endif
 
-        /* Normally, these are cleaned by linker_env_secure, but the test
-         * against program_is_setuid doesn't cost us anything */
-        if (!program_is_setuid) {
-            ldpath_env = linker_env_get("LD_LIBRARY_PATH");
-            ldpreload_env = linker_env_get("LD_PRELOAD");
-        }
+    // Normally, these are cleaned by linker_env_init, but the test
+    // doesn't cost us anything.
+    const char* ldpath_env = NULL;
+    const char* ldpreload_env = NULL;
+    if (!get_AT_SECURE()) {
+      ldpath_env = linker_env_get("LD_LIBRARY_PATH");
+      ldpreload_env = linker_env_get("LD_PRELOAD");
     }
 
     INFO("[ android linker & debugger ]\n");
     DEBUG("%5d elfdata @ 0x%08x\n", pid, (unsigned)elfdata);
 
-    si = soinfo_alloc(argv[0]);
-    if(si == 0) {
-        exit(-1);
+    soinfo* si = soinfo_alloc(argv[0]);
+    if (si == NULL) {
+        exit(EXIT_FAILURE);
     }
 
     /* bootstrap the link map, the main exe always needs to be first */
@@ -1858,7 +1831,7 @@ sanitize:
     insert_soinfo_into_debug_map(&linker_soinfo);
 
     /* extract information passed from the kernel */
-    while(vecs[0] != 0){
+    while (vecs[0] != 0){
         switch(vecs[0]){
         case AT_PHDR:
             si->phdr = (Elf32_Phdr*) vecs[1];
@@ -1899,12 +1872,12 @@ sanitize:
         char errmsg[] = "CANNOT LINK EXECUTABLE\n";
         write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
         write(2, errmsg, sizeof(errmsg));
-        exit(-1);
+        exit(EXIT_FAILURE);
     }
 
     soinfo_call_preinit_constructors(si);
 
-    for(i = 0; preloads[i] != NULL; i++) {
+    for (size_t i = 0; preloads[i] != NULL; ++i) {
         soinfo_call_constructors(preloads[i]);
     }
 
@@ -2049,7 +2022,7 @@ extern "C" unsigned __linker_init(unsigned **elfdata) {
         //
         // This situation should never occur unless the linker itself
         // is corrupt.
-        exit(-1);
+        exit(EXIT_FAILURE);
     }
 
     // We have successfully fixed our own relocations. It's safe to run