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[binutils-gdb] Fix displaced-stepping RIP-relative VEX-encoded instructions (AVX) (PR gdb/22499)
- From: sergiodj+buildbot at sergiodj dot net
- To: gdb-testers at sourceware dot org
- Date: Mon, 04 Dec 2017 11:38:55 -0500
- Subject: [binutils-gdb] Fix displaced-stepping RIP-relative VEX-encoded instructions (AVX) (PR gdb/22499)
- Authentication-results: sourceware.org; auth=none
*** TEST RESULTS FOR COMMIT 50a1fdd59c1777672a9be0e81fe2301c2a115fce ***
Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: 50a1fdd59c1777672a9be0e81fe2301c2a115fce
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.
- Follow-Ups:
- Failures on Fedora-i686, branch master
- Failures on Fedora-x86_64-m64, branch master
- Failures on Fedora-x86_64-m32, branch master
- Failures on Fedora-x86_64-native-gdbserver-m32, branch master
- Failures on Ubuntu-AArch32-native-extended-gdbserver-m32, branch master
- Failures on Fedora-s390x-m64, branch master
- Failures on Fedora-x86_64-native-extended-gdbserver-m32, branch master
- Failures on Fedora-x86_64-native-gdbserver-m64, branch master
- Failures on Ubuntu-AArch32-native-gdbserver-m32, branch master
- Failures on Ubuntu-AArch64-m64, branch master
- Failures on Fedora-x86_64-cc-with-index, branch master