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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2019-04-29 11:27:57 -0400
committerShuah Khan <skhan@linuxfoundation.org>2019-05-07 15:32:05 -0600
commit24fa5d1efe98bc09a96ba41fdba96ef715aede77 (patch)
tree99f5bf1cdb52d77a8c46114ab438711c4bcaf4ff /tools
parentrseq/selftests: s390: use jg instruction for jumps outside of the asm (diff)
downloadlinux-dev-24fa5d1efe98bc09a96ba41fdba96ef715aede77.tar.xz
linux-dev-24fa5d1efe98bc09a96ba41fdba96ef715aede77.zip
rseq/selftests: x86: use ud1 instruction as RSEQ_SIG opcode
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>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/rseq/rseq-x86.h15
1 files changed, 11 insertions, 4 deletions
diff --git a/tools/testing/selftests/rseq/rseq-x86.h b/tools/testing/selftests/rseq/rseq-x86.h
index 03095236f6fa..b2da6004fe30 100644
--- a/tools/testing/selftests/rseq/rseq-x86.h
+++ b/tools/testing/selftests/rseq/rseq-x86.h
@@ -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 \