i#58 MacOS: dyld shared cache on 10.9

Switch to symbol lookup to find dyld shared cache lib list, as the offset
is not supported on OSX 10.9.  This requires adding functionality to walk the
symbol table.

SVN-Revision: 2541

core/unix/module.h

@@ -87,6 +87,10 @@ typedef struct _os_module_data_t {
 #else /* MACOS */
     byte *exports;        /* absolute addr of exports trie */
     size_t exports_sz;    /* size of exports trie */
+    byte *symtab;
+    uint num_syms;
+    byte *strtab;
+    size_t strtab_sz;
 #endif
 
     /* i#160/PR 562667: support non-contiguous library mappings */

core/unix/module_macho.c

@@ -54,6 +54,7 @@
 #include <mach-o/loader.h> /* mach_header */
 #include <mach-o/dyld_images.h>
 #include <mach/thread_status.h> /* i386_thread_state_t */
+#include <mach-o/nlist.h>
 #include <sys/syscall.h>
 #include <stddef.h> /* offsetof */
 #include <string.h> /* strcmp */
@@ -71,9 +72,11 @@
 #ifdef X64
 typedef struct mach_header_64 mach_header_t;
 typedef struct segment_command_64 segment_command_t;
+typedef struct nlist_64 nlist_t;
 #else
 typedef struct mach_header mach_header_t;
 typedef struct segment_command segment_command_t;
+typedef struct nlist nlist_t;
 #endif
 
 /* Like is_elf_so_header(), if size == 0 then safe-reads the header; else
@@ -198,6 +201,10 @@ module_walk_program_headers(app_pc base, size_t view_size, bool at_map,
     }
     if (found_seg) {
         ptr_int_t load_delta = base - seg_min_start;
+        ptr_int_t linkedit_delta = 0;
+        if (linkedit_file_off > 0) {
+            linkedit_delta = ((ssize_t)linkedit_mem_off - linkedit_file_off);
+        }
         LOG(GLOBAL, LOG_VMAREAS, 4, "%s: bounds "PFX"-"PFX"\n", __FUNCTION__,
             seg_min_start, seg_max_end);
         if (out_base != NULL)
@@ -233,6 +240,15 @@ module_walk_program_headers(app_pc base, size_t view_size, bool at_map,
                              have_shared && seg_start >= shared_start &&
                              seg_start + seg->vmsize < shared_end);
                     }
+                } else if (cmd->cmd == LC_SYMTAB) {
+                    /* even if stripped, dynamic symbols are in this table */
+                    struct symtab_command *symtab = (struct symtab_command *) cmd;
+                    out_data->symtab = (app_pc) symtab->symoff + load_delta +
+                        linkedit_delta;
+                    out_data->num_syms = symtab->nsyms;
+                    out_data->strtab = (app_pc) symtab->stroff + load_delta +
+                        linkedit_delta;
+                    out_data->strtab_sz = symtab->strsize;
                 }
                 cmd = (struct load_command *)((byte *)cmd + cmd->cmdsize);
             }
@@ -241,9 +257,9 @@ module_walk_program_headers(app_pc base, size_t view_size, bool at_map,
              */
             out_data->base_address = seg_min_start;
             out_data->alignment = PAGE_SIZE; /* FIXME i#58: need min section align? */
-            if (linkedit_file_off > 0) {
+            if (linkedit_file_off > 0 && exports_file_off > 0) {
                 out_data->exports = (app_pc) load_delta + exports_file_off +
-                    ((ssize_t)linkedit_mem_off - linkedit_file_off);
+                    linkedit_delta;
             } else
                 out_data->exports = NULL;
         }
@@ -339,6 +355,10 @@ get_proc_address_from_os_data(os_module_data_t *os_data,
 {
     /* Walk the Mach-O export trie.  We don't support < 10.6 which is when
      * they put this scheme in place.
+     * XXX: should we go ahead and look in symtab if we don't find it in
+     * the trie?  That could include internal symbols too.  Plus our
+     * current lookup_in_symtab() is a linear walk.  Xref drsyms which sorts
+     * it and does a binary search.
      */
     app_pc res = NULL;
     ptr_uint_t node_sz, node_offs;
@@ -564,14 +584,54 @@ module_dyld_shared_region(app_pc *start OUT, app_pc *end OUT)
     return true;
 }
 
+/* Brute force linear walk lookup */
+static app_pc
+lookup_in_symtab(app_pc lib_base, const char *symbol)
+{
+    app_pc res = NULL;
+    module_area_t *ma;
+    os_get_module_info_lock();
+    ma = module_pc_lookup(lib_base);
+    if (ma != NULL) {
+        uint i;
+        for (i = 0; i < ma->os_data.num_syms; i++) {
+            nlist_t *sym = ((nlist_t *)(ma->os_data.symtab)) + i;
+            const char *name;
+            if (sym->n_un.n_strx > 0 && sym->n_un.n_strx < ma->os_data.strtab_sz &&
+                sym->n_value > 0) {
+                name = (const char *)ma->os_data.strtab + sym->n_un.n_strx;
+                if (name[0] == '_')
+                    name++;
+                LOG(GLOBAL, LOG_SYMBOLS, 5, "\tsym %d = %s\n", i, name);
+                if (strcmp(name, symbol) == 0) {
+                    res = (app_pc)(sym->n_value + ma->start - ma->os_data.base_address);
+                    break;
+                }
+            }
+        }
+    }
+    os_get_module_info_unlock();
+    LOG(GLOBAL, LOG_SYMBOLS, 2, "%s: %s => "PFX"\n", __func__, symbol, res);
+    return res;
+}
+
 void
 module_walk_dyld_list(app_pc dyld_base)
 {
-    uint i, offs;
+    uint i;
     struct dyld_all_image_infos *dyinfo;
-    /* We only support OSX 10.6+ so we can use this offset */
-    offs = *(uint *)(dyld_base + DYLD_ALL_IMAGE_INFOS_OFFSET_OFFSET);
-    dyinfo = (struct dyld_all_image_infos *)(dyld_base + offs);
+    /* The DYLD_ALL_IMAGE_INFOS_OFFSET_OFFSET added in 10.6 seems to not
+     * exist in 10.9 anymore so we do not use it.  Instead we directly
+     * look up "dyld_all_image_infos".  Unfortunately dyld has no exports
+     * trie and so we must walk the symbol table.
+     */
+    dyinfo = (struct dyld_all_image_infos *)
+        lookup_in_symtab(dyld_base, "dyld_all_image_infos");
+    /* We rely on this -- so until Mac support is more solid let's assert */
+    if (dyinfo == NULL || !is_readable_without_exception((byte *)dyinfo, PAGE_SIZE)) {
+        SYSLOG_INTERNAL_WARNING("failed to walk dyld shared cache libraries");
+        return;
+    }
     LOG(GLOBAL, LOG_VMAREAS, 2,
         "Walking %d modules in dyld module list\n", dyinfo->infoArrayCount);
     for (i = 0; i < dyinfo->infoArrayCount; i++) {