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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.
67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
/* Copyright (C) 2015-2016 Free Software Foundation, Inc.
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Contributed by Intel Corp. <walfred.tedeschi@intel.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "x86-cpuid.h"
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#include <stdio.h>
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#define OUR_SIZE 5
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unsigned int
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have_mpx (void)
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{
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unsigned int eax, ebx, ecx, edx;
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if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
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return 0;
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if ((ecx & bit_OSXSAVE) == bit_OSXSAVE)
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{
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if (__get_cpuid_max (0, NULL) < 7)
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return 0;
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__cpuid_count (7, 0, eax, ebx, ecx, edx);
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if ((ebx & bit_MPX) == bit_MPX)
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return 1;
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else
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return 0;
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}
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return 0;
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}
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void
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upper (int * p, int len)
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{
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int value;
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len++; /* b0-size-test. */
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value = *(p + len);
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}
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int
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main (void)
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{
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if (have_mpx ())
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{
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int a = 0; /* Dummy variable for debugging purposes. */
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int sx[OUR_SIZE];
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a++; /* register-eval. */
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upper (sx, OUR_SIZE + 2);
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return sx[1];
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}
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return 0;
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}
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