2018-01-01 12:43:02 +08:00
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/* Copyright 2009-2018 Free Software Foundation, Inc.
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Fix displaced-stepping RIP-relative VEX-encoded instructions (AVX) (PR gdb/22499)
PR gdb/22499 is about a latent bug exposed by the switch to "maint set
target-non-stop on" by default on x86-64 GNU/Linux, a while ago. With
that on, GDB is also preferring to use displaced-stepping by default.
The testcase in the bug is failing because GDB ends up incorrectly
displaced-stepping over a RIP-relative VEX-encoded instruction, like
this:
0x00000000004007f5 <+15>: c5 fb 10 05 8b 01 00 00 vmovsd 0x18b(%rip),%xmm0 # 0x400988
While RIP-relative instructions need adjustment when relocated to the
scratch pad, GDB ends up just copying VEX-encoded instructions to the
scratch pad unmodified, with the end result that the inferior ends up
executing an instruction that fetches/writes memory from the wrong
address...
This patch teaches GDB about the VEX-encoding prefixes, fixing the
problem, and adds a testcase that fails without the GDB fix.
I think we may need a similar treatment for EVEX-encoded instructions,
but I didn't address that simply because I couldn't find any
EVEX-encoded RIP-relative instruction in the gas testsuite. In any
case, this commit is forward progress as-is already.
gdb/ChangeLog:
2017-12-04 Pedro Alves <palves@redhat.com>
PR gdb/22499
* amd64-tdep.c (amd64_insn::rex_offset): Rename to...
(amd64_insn::enc_prefix_offset): ... this, and tweak comment.
(vex2_prefix_p, vex3_prefix_p): New functions.
(amd64_get_insn_details): Adjust to rename. Also skip VEX2 and
VEX3 prefixes.
(fixup_riprel): Set VEX3.!B.
gdb/testsuite/ChangeLog:
2017-12-04 Pedro Alves <palves@redhat.com>
PR gdb/22499
* gdb.arch/amd64-disp-step-avx.S: New file.
* gdb.arch/amd64-disp-step-avx.exp: New file.
2017-12-04 23:59:20 +08:00
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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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This file is part of the gdb testsuite.
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Test displaced stepping over VEX-encoded RIP-relative AVX
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instructions. */
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.text
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.global main
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main:
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nop
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/***********************************************/
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/* Test a VEX2-encoded RIP-relative instruction. */
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.global test_rip_vex2
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test_rip_vex2:
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vmovsd ro_var(%rip),%xmm0
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.global test_rip_vex2
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test_rip_vex2_end:
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nop
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/* Test a VEX3-encoded RIP-relative instruction. */
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.global test_rip_vex3
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test_rip_vex3:
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vextractf128 $0x0,%ymm0,var128(%rip)
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.global test_rip_vex3
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test_rip_vex3_end:
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nop
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/* skip over test data */
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jmp done
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/* RIP-relative ro-data for VEX2 test above. */
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ro_var:
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.8byte 0x1122334455667788
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.8byte 0x8877665544332211
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/***********************************************/
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/* All done. */
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done:
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mov $0,%rdi
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call exit
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hlt
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/* RIP-relative data for VEX3 test above. */
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.data
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var128:
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.8byte 0xaa55aa55aa55aa55
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.8byte 0x55aa55aa55aa55aa
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