SA does not work if executable is DSO

[Yasumasa Suenaga]

Hi all,

In modern Linux e.g. Fedora 25, executables are built as DSO for security [1].
java command in OpenJDK which is provided by distribution is also DSO.
However, SA does not work with DSO executables.

I want to propose the fix as below.

------------------------
diff -r a26b9492461b src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c
--- a/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c	Wed Feb 01 17:56:22 2017 -0500
+++ b/src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c	Sun Feb 05 23:13:19 2017 +0900
@@ -642,6 +642,9 @@
          if (core_handle_prstatus(ph, descdata, notep->n_descsz) != true) {
            return false;
          }
+      } else if (notep->n_type == NT_FILE) {
+        // Skip "count", "page_size" in NT_FILE
+        memcpy(&ph->core->dynamic_addr, ((long *)descdata) + 2, sizeof(long));
        }
        p = descdata + ROUNDUP(notep->n_descsz, 4);
     }
@@ -832,7 +835,11 @@
  
      // 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
+        ph->core->dynamic_addr += exec_php->p_offset;
+      }
        print_debug("address of _DYNAMIC is 0x%lx\n", ph->core->dynamic_addr);
        break;
      }
@@ -1030,8 +1037,9 @@
      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;
    }
  
------------------------

Currently, OpenJDK 8 in Fedora25 is built as DSO.
So I want to contribute this patch to JDK 8 or later release.

Can I file it to JBS and can send review request?


Thanks,

Yasumasa


[1] https://fedoraproject.org/wiki/Packaging:Guidelines#PIE