gdb/rs6000: Read backchain as unsigned.

Previously, backchain was read as a signed quantity, resulting in
addresses like 0xfffffffffffeded0 instead of 0xfffeded0 returned by
unwinder on 32-bit powerpc.  While normally such addresses are masked
off, this causes problems for tracepoints, since 0xfffffffffffeded0
is considered unavailable.

Fixes a test failure in gdb.trace/entry-values.exp.

gdb/ChangeLog:

	* corefile.c (safe_read_memory_unsigned_integer): New function.
	* gdbcore.h (safe_read_memory_unsigned_integer): New prototype.
	* rs6000-tdep.c (rs6000_frame_cache): Read backchain as unsigned.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 74dec87054b6d2ae50468a74ba203df7d7966db0..83eef3747495239bc3d26c1be17e5f50a4dc477f 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-09  Marcin Kościelnicki  <koriakin@0x04.net>
+
+       * corefile.c (safe_read_memory_unsigned_integer): New function.
+       * gdbcore.h (safe_read_memory_unsigned_integer): New prototype.
+       * rs6000-tdep.c (rs6000_frame_cache): Read backchain as unsigned.
+
 2016-03-09  Marcin Kościelnicki  <koriakin@0x04.net>
 
        * rs6000-tdep.c: Add "ax.h" and "ax-gdb.h" includes.

diff --git a/gdb/corefile.c b/gdb/corefile.c
index dbdbafc41f14ac593d952245d1c17bdedae2e7e5..5ad4d40ec66f703569ce7250184cb35c08bbc28e 100644 (file)
--- a/gdb/corefile.c
+++ b/gdb/corefile.c
@@ -306,6 +306,24 @@ safe_read_memory_integer (CORE_ADDR memaddr, int len,
   return 1;
 }
 
+/* Read memory at MEMADDR of length LEN and put the contents in
+   RETURN_VALUE.  Return 0 if MEMADDR couldn't be read and non-zero
+   if successful.  */
+
+int
+safe_read_memory_unsigned_integer (CORE_ADDR memaddr, int len,
+                                  enum bfd_endian byte_order,
+                                  ULONGEST *return_value)
+{
+  gdb_byte buf[sizeof (ULONGEST)];
+
+  if (target_read_memory (memaddr, buf, len))
+    return 0;
+
+  *return_value = extract_unsigned_integer (buf, len, byte_order);
+  return 1;
+}
+
 LONGEST
 read_memory_integer (CORE_ADDR memaddr, int len,
                     enum bfd_endian byte_order)

diff --git a/gdb/gdbcore.h b/gdb/gdbcore.h
index 5db80e56a131e22efb93daf2a196c50398955379..8b101bcabef81c9847ac14f1d5b2d9692c2fd9dd 100644 (file)
--- a/gdb/gdbcore.h
+++ b/gdb/gdbcore.h
@@ -76,6 +76,9 @@ extern int safe_read_memory_integer (CORE_ADDR memaddr, int len,
 extern ULONGEST read_memory_unsigned_integer (CORE_ADDR memaddr,
                                              int len,
                                              enum bfd_endian byte_order);
+extern int safe_read_memory_unsigned_integer (CORE_ADDR memaddr, int len,
+                                             enum bfd_endian byte_order,
+                                             ULONGEST *return_value);
 
 /* Read an integer from debugged code memory, given address,
    number of bytes, and byte order for code.  */

diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 565c6201bcee3d8ab5fad68babac8619c69c5331..2460eb5b8d8d594e4d33fd98c18d06634c71be8e 100644 (file)
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -3336,10 +3336,10 @@ rs6000_frame_cache (struct frame_info *this_frame, void **this_cache)
   if (!fdata.frameless)
     {
       /* Frameless really means stackless.  */
-      LONGEST backchain;
+      ULONGEST backchain;
 
-      if (safe_read_memory_integer (cache->base, wordsize,
-                                   byte_order, &backchain))
+      if (safe_read_memory_unsigned_integer (cache->base, wordsize,
+                                            byte_order, &backchain))
         cache->base = (CORE_ADDR) backchain;
     }