Intel MPX bound violation handling

With Intel Memory Protection Extensions it was introduced the concept of
boundary violation.  A boundary violations is presented to the inferior as
a segmentation fault having SIGCODE 3.  This patch adds a
handler for a boundary violation extending the information displayed
when a bound violation is presented to the inferior.  In the stop mode
case the debugger will also display the kind of violation: "upper" or
"lower", bounds and the address accessed.
On no stop mode the information will still remain unchanged.  Additional
information about bound violations are not meaningful in that case user
does not know the line in which violation occurred as well.

When the segmentation fault handler is stop mode the out puts will be
changed as exemplified below.

The usual output of a segfault is:
Program received signal SIGSEGV, Segmentation fault
0x0000000000400d7c in upper (p=0x603010, a=0x603030, b=0x603050,
c=0x603070, d=0x603090, len=7) at i386-mpx-sigsegv.c:68
68        value = *(p + len);

In case it is a bound violation it will be presented as:
Program received signal SIGSEGV, Segmentation fault
Upper bound violation while accessing address 0x7fffffffc3b3
Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
0x0000000000400d7c in upper (p=0x603010, a=0x603030, b=0x603050,
c=0x603070, d=0x603090, len=7) at i386-mpx-sigsegv.c:68
68        value = *(p + len);

In mi mode the output of a segfault is:
*stopped,reason="signal-received",signal-name="SIGSEGV",
signal-meaning="Segmentation fault", frame={addr="0x0000000000400d7c",
func="upper",args=[{name="p", value="0x603010"},{name="a",value="0x603030"}
,{name="b",value="0x603050"}, {name="c",value="0x603070"},
{name="d",value="0x603090"},{name="len",value="7"}],
file="i386-mpx-sigsegv.c",fullname="i386-mpx-sigsegv.c",line="68"},
thread-id="1",stopped-threads="all",core="6"

in the case of a bound violation:
*stopped,reason="signal-received",signal-name="SIGSEGV",
signal-meaning="Segmentation fault",
sigcode-meaning="Upper bound violation",
lower-bound="0x603010",upper-bound="0x603023",bound-access="0x60302f",
frame={addr="0x0000000000400d7c",func="upper",args=[{name="p",
value="0x603010"},{name="a",value="0x603030"},{name="b",value="0x603050"},
{name="c",value="0x603070"},{name="d",value="0x603090"},
{name="len",value="7"}],file="i386-mpx-sigsegv.c",
fullname="i386-mpx-sigsegv.c",line="68"},thread-id="1",
stopped-threads="all",core="6"

2016-02-18  Walfred Tedeschi  <walfred.tedeschi@intel.com>

gdb/ChangeLog:

	* NEWS: Add entry for bound violation.
	* amd64-linux-tdep.c (amd64_linux_init_abi_common):
	Add handler for segmentation fault.
	* gdbarch.sh (handle_segmentation_fault): New.
	* gdbarch.c: Regenerate.
	* gdbarch.h: Regenerate.
	* i386-linux-tdep.c (i386_linux_handle_segmentation_fault): New.
	(SIG_CODE_BONDARY_FAULT): New define.
	(i386_linux_init_abi): Use i386_mpx_bound_violation_handler.
	* i386-linux-tdep.h (i386_linux_handle_segmentation_fault) New.
	* i386-tdep.c (i386_mpx_enabled): Add as external.
	* i386-tdep.c (i386_mpx_enabled): Add as external.
	* infrun.c (handle_segmentation_fault): New function.
	(print_signal_received_reason): Use handle_segmentation_fault.

gdb/testsuite/ChangeLog:

	* gdb.arch/i386-mpx-sigsegv.c: New file.
	* gdb.arch/i386-mpx-sigsegv.exp: New file.
	* gdb.arch/i386-mpx-simple_segv.c: New file.
	* gdb.arch/i386-mpx-simple_segv.exp: New file.

gdb/doc/ChangeLog:

	* gdb.texinfo (Signals): Add bound violation display hints for
	a SIGSEGV.

1 files changed, 18 insertions, 0 deletions

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 15210c9..3e8c9e0 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7904,6 +7904,20 @@ print_exited_reason (struct ui_out *uiout, int exitstatus)
     }
 }
 
+/* Some targets/architectures can do extra processing/display of
+   segmentation faults.  E.g., Intel MPX boundary faults.
+   Call the architecture dependent function to handle the fault.  */
+
+static void
+handle_segmentation_fault (struct ui_out *uiout)
+{
+  struct regcache *regcache = get_current_regcache ();
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
+
+  if (gdbarch_handle_segmentation_fault_p (gdbarch))
+    gdbarch_handle_segmentation_fault (gdbarch, uiout);
+}
+
 void
 print_signal_received_reason (struct ui_out *uiout, enum gdb_signal siggnal)
 {
@@ -7947,6 +7961,10 @@ print_signal_received_reason (struct ui_out *uiout, enum gdb_signal siggnal)
       annotate_signal_string ();
       ui_out_field_string (uiout, "signal-meaning",
 			   gdb_signal_to_string (siggnal));
+
+      if (siggnal == GDB_SIGNAL_SEGV)
+	handle_segmentation_fault (uiout);
+
       annotate_signal_string_end ();
     }
   ui_out_text (uiout, ".\n");