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rseq/selftests: x86: use ud1 instruction as RSEQ_SIG opcode

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Use ud1 as the guard instruction for the restartable sequence abort
handler. Its benefit compared to nopl is to trap execution if the
program ends up trying to execute it by mistake, which makes debugging
easier.

The 4-byte signature per se is unchanged (it is the instruction
operand). Only the opcode is changed from nopl to ud1.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Joel Fernandes <joelaf@google.com>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Dave Watson <davejwatson@fb.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Shuah Khan <shuah@kernel.org>
CC: Andi Kleen <andi@firstfloor.org>
CC: linux-kselftest@vger.kernel.org
CC: "H . Peter Anvin" <hpa@zytor.com>
CC: Chris Lameter <cl@linux.com>
CC: Russell King <linux@arm.linux.org.uk>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
CC: Paul Turner <pjt@google.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Ben Maurer <bmaurer@fb.com>
CC: linux-api@vger.kernel.org
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
Mathieu Desnoyers 2019-04-29 11:27:57 -04:00 committed by Shuah Khan
parent 97b8be8168
commit 24fa5d1efe
1 changed files with 11 additions and 4 deletions
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15
tools/testing/selftests/rseq/rseq-x86.h
View file

@ -7,6 +7,13 @@
#include <stdint.h>
/*
* RSEQ_SIG is used with the following reserved undefined instructions, which
* trap in user-space:
*
* x86-32: 0f b9 3d 53 30 05 53 ud1 0x53053053,%edi
* x86-64: 0f b9 3d 53 30 05 53 ud1 0x53053053(%rip),%edi
*/
#define RSEQ_SIG 0x53053053
/*
@ -88,8 +95,8 @@ do { \
#define RSEQ_ASM_DEFINE_ABORT(label, teardown, abort_label) \
".pushsection __rseq_failure, \"ax\"\n\t" \
/* Disassembler-friendly signature: nopl <sig>(%rip). */\
".byte 0x0f, 0x1f, 0x05\n\t" \
/* Disassembler-friendly signature: ud1 <sig>(%rip),%edi. */ \
".byte 0x0f, 0xb9, 0x3d\n\t" \
".long " __rseq_str(RSEQ_SIG) "\n\t" \
__rseq_str(label) ":\n\t" \
teardown \
@ -609,8 +616,8 @@ do { \
#define RSEQ_ASM_DEFINE_ABORT(label, teardown, abort_label) \
".pushsection __rseq_failure, \"ax\"\n\t" \
/* Disassembler-friendly signature: nopl <sig>. */ \
".byte 0x0f, 0x1f, 0x05\n\t" \
/* Disassembler-friendly signature: ud1 <sig>,%edi. */ \
".byte 0x0f, 0xb9, 0x3d\n\t" \
".long " __rseq_str(RSEQ_SIG) "\n\t" \
__rseq_str(label) ":\n\t" \
teardown \