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Pedro Alves 50a1fdd59c 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 15:59:20 +00:00
bfd x86 map file textrel 2017-12-04 23:05:01 +10:30
binutils Add --strip-unneeded to objcopy synopsis 2017-12-01 19:08:42 +10:30
config
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gas Documentation fix 2017-12-04 22:26:32 +10:30
gdb Fix displaced-stepping RIP-relative VEX-encoded instructions (AVX) (PR gdb/22499) 2017-12-04 15:59:20 +00:00
gold Handle case where posix_fallocate is not supported for a filesystem. 2017-12-02 09:56:40 -08:00
gprof Support --localedir, --datarootdir and --datadir 2017-11-29 20:10:52 +10:30
include Use consistent types for holding instructions, instruction masks, etc. 2017-12-01 11:20:15 -06:00
intl
ld x86 map file textrel 2017-12-04 23:05:01 +10:30
libdecnumber
libiberty
opcodes Fix "FAIL: VLE relocations 3" 2017-12-03 21:54:47 +10:30
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depcomp Update from upstream Automake 2014-11-16 13:43:48 +01:00
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move-if-change Update `move-if-change' from gnulib 2014-11-16 17:04:02 +01:00
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		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.