[PATCH 3/8] gdb/rs6000: Read backchain as unsigned.

Marcin Kościelnicki
2016-03-06T16:40:16Z

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.
---
gdb/ChangeLog | 6 ++++++
gdb/corefile.c | 18 ++++++++++++++++++
gdb/gdbcore.h | 3 +++
gdb/rs6000-tdep.c | 6 +++---
4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c2ef019..45c5276 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-06 Marcin KoÅ›cielnicki <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.
+
2016-03-05 Marcin KoÅ›cielnicki <koriakin@0x04.net>

* rs6000-tdep.c (rs6000_gen_return_address): New function.
diff --git a/gdb/corefile.c b/gdb/corefile.c
index dbdbafc..5ad4d40 100644
--- 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 5db80e5..8b101bc 100644
--- 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 565c620..2460eb5 100644
--- 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;
}

--
2.7.2