From aa3bb307a30a5b78bf1ae4ac843ae53e354736f5 Mon Sep 17 00:00:00 2001
From: Arun Sharma <arun@sharma-home.net>
Date: Mon, 3 May 2010 07:47:28 -0700
Subject: [PATCH] Fix merge errors

---
 src/x86_64/Gos-linux.c |  1 +
 src/x86_64/Gstep.c     | 36 +++++++++++++++++++++++++++++++++---
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/src/x86_64/Gos-linux.c b/src/x86_64/Gos-linux.c
index 957f3e30..b7f832ca 100644
--- a/src/x86_64/Gos-linux.c
+++ b/src/x86_64/Gos-linux.c
@@ -93,6 +93,7 @@ unw_handle_signal_frame (unw_cursor_t *cursor)
      Hence dwarf_step() should never call this function. Maybe
      restore old non-dwarf signal handling here, but then the
      gating on unw_is_signal_frame() needs to be removed. */
+  struct cursor *c = (struct cursor *) cursor;
   Debug(1, "old format signal frame? format=%d addr=0x%lx cfa=0x%lx\n",
 	c->sigcontext_format, c->sigcontext_addr, c->dwarf.cfa);
   assert(c->sigcontext_format == X86_64_SCF_LINUX_RT_SIGFRAME);
diff --git a/src/x86_64/Gstep.c b/src/x86_64/Gstep.c
index 237811ce..85e3989a 100644
--- a/src/x86_64/Gstep.c
+++ b/src/x86_64/Gstep.c
@@ -28,14 +28,38 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 #include <signal.h>
 
+/* Recognise PLT entries such as:
+     3bdf0: ff 25 e2 49 13 00 jmpq   *0x1349e2(%rip)
+     3bdf6: 68 ae 03 00 00    pushq  $0x3ae
+     3bdfb: e9 00 c5 ff ff    jmpq   38300 <_init+0x18> */
+static int
+is_plt_entry (struct dwarf_cursor *c)
+{
+  unw_word_t w0, w1;
+  unw_accessors_t *a;
+  int ret;
+
+  a = unw_get_accessors (c->as);
+  if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
+      || (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
+    return 0;
+
+  ret = (((w0 & 0xffff) == 0x25ff)
+	 && (((w0 >> 48) & 0xff) == 0x68)
+	 && (((w1 >> 24) & 0xff) == 0xe9));
+
+  Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
+  return ret;
+}
+
 PROTECTED int
 unw_step (unw_cursor_t *cursor)
 {
   struct cursor *c = (struct cursor *) cursor;
   int ret, i;
 
-  Debug (1, "(cursor=%p, ip=0x%016llx)\n",
-	 c, (unsigned long long) c->dwarf.ip);
+  Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n",
+	 c, c->dwarf.ip, c->dwarf.cfa);
 
   /* Try DWARF-based unwinding... */
   c->sigcontext_format = X86_64_SCF_NONE;
@@ -86,6 +110,12 @@ unw_step (unw_cursor_t *cursor)
 	      return 0;
 	    }
 	}
+      else if (is_plt_entry (&c->dwarf))
+	{
+	  Debug (2, "found plt entry\n");
+          c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
+          c->dwarf.cfa += 8;
+	}
       else if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
         {
 	  for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
@@ -139,7 +169,7 @@ unw_step (unw_cursor_t *cursor)
 
       c->dwarf.ret_addr_column = RIP;
 
-      if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
+      if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP]))
 	{
 	  ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
 	  Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",