8173941: SA does not work if executable is DSO

Reviewed-by: aph, dsamersoff

agent/src/os/linux/elfmacros.h

@@ -33,6 +33,7 @@
 #define ELF_NHDR        Elf64_Nhdr
 #define ELF_DYN         Elf64_Dyn
 #define ELF_ADDR        Elf64_Addr
+#define ELF_AUXV        Elf64_auxv_t
 
 #define ELF_ST_TYPE     ELF64_ST_TYPE
 
@@ -45,6 +46,7 @@
 #define ELF_NHDR        Elf32_Nhdr
 #define ELF_DYN         Elf32_Dyn
 #define ELF_ADDR        Elf32_Addr
+#define ELF_AUXV        Elf32_auxv_t
 
 #define ELF_ST_TYPE     ELF32_ST_TYPE
 

agent/src/os/linux/ps_core.c

@@ -642,6 +642,18 @@ static bool core_handle_note(struct ps_prochandle* ph, ELF_PHDR* note_phdr) {
         if (core_handle_prstatus(ph, descdata, notep->n_descsz) != true) {
           return false;
         }
+      } else if (notep->n_type == NT_AUXV) {
+        // Get first segment from entry point
+        ELF_AUXV *auxv = (ELF_AUXV *)descdata;
+        while (auxv->a_type != AT_NULL) {
+          if (auxv->a_type == AT_ENTRY) {
+            // Set entry point address to address of dynamic section.
+            // We will adjust it in read_exec_segments().
+            ph->core->dynamic_addr = auxv->a_un.a_val;
+            break;
+          }
+          auxv++;
+        }
       }
       p = descdata + ROUNDUP(notep->n_descsz, 4);
    }
@@ -826,7 +838,13 @@ static bool read_exec_segments(struct ps_prochandle* ph, ELF_EHDR* exec_ehdr) {
 
          // from PT_DYNAMIC we want to read address of first link_map addr
          case PT_DYNAMIC: {
-            ph->core->dynamic_addr = exec_php->p_vaddr;
+            if (exec_ehdr->e_type == ET_EXEC) {
+                ph->core->dynamic_addr = exec_php->p_vaddr;
+            } else { // ET_DYN
+                // dynamic_addr has entry point of executable.
+                // Thus we should substract it.
+                ph->core->dynamic_addr += exec_php->p_vaddr - exec_ehdr->e_entry;
+            }
             print_debug("address of _DYNAMIC is 0x%lx\n", ph->core->dynamic_addr);
             break;
          }
@@ -1024,8 +1042,9 @@ struct ps_prochandle* Pgrab_core(const char* exec_file, const char* core_file) {
     goto err;
   }
 
-  if (read_elf_header(ph->core->exec_fd, &exec_ehdr) != true || exec_ehdr.e_type != ET_EXEC) {
-    print_debug("executable file is not a valid ELF ET_EXEC file\n");
+  if (read_elf_header(ph->core->exec_fd, &exec_ehdr) != true ||
+      ((exec_ehdr.e_type != ET_EXEC) && (exec_ehdr.e_type != ET_DYN))) {
+    print_debug("executable file is not a valid ELF file\n");
     goto err;
   }