From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.desnoyers at efficios.com (Mathieu Desnoyers) Date: Mon, 29 Apr 2019 11:27:57 -0400 Subject: [PATCH for 5.2 06/12] rseq/selftests: x86: use ud1 instruction as RSEQ_SIG opcode In-Reply-To: <20190429152803.7719-1-mathieu.desnoyers@efficios.com> References: <20190429152803.7719-1-mathieu.desnoyers@efficios.com> Message-ID: <20190429152803.7719-7-mathieu.desnoyers@efficios.com> 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 Suggested-by: Peter Zijlstra CC: Peter Zijlstra CC: Thomas Gleixner CC: Joel Fernandes CC: Catalin Marinas CC: Dave Watson CC: Will Deacon CC: Shuah Khan CC: Andi Kleen CC: linux-kselftest at vger.kernel.org CC: "H . Peter Anvin" CC: Chris Lameter CC: Russell King CC: Michael Kerrisk CC: "Paul E . McKenney" CC: Paul Turner CC: Boqun Feng CC: Josh Triplett CC: Steven Rostedt CC: Ben Maurer CC: linux-api at vger.kernel.org CC: Andy Lutomirski CC: Andrew Morton CC: Linus Torvalds --- tools/testing/selftests/rseq/rseq-x86.h | 15 +++++++++++---- 1 file 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 +/* + * 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 (%rip). */\ - ".byte 0x0f, 0x1f, 0x05\n\t" \ + /* Disassembler-friendly signature: ud1 (%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 . */ \ - ".byte 0x0f, 0x1f, 0x05\n\t" \ + /* Disassembler-friendly signature: ud1 ,%edi. */ \ + ".byte 0x0f, 0xb9, 0x3d\n\t" \ ".long " __rseq_str(RSEQ_SIG) "\n\t" \ __rseq_str(label) ":\n\t" \ teardown \ -- 2.11.0 From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers) Date: Mon, 29 Apr 2019 11:27:57 -0400 Subject: [PATCH for 5.2 06/12] rseq/selftests: x86: use ud1 instruction as RSEQ_SIG opcode In-Reply-To: <20190429152803.7719-1-mathieu.desnoyers@efficios.com> References: <20190429152803.7719-1-mathieu.desnoyers@efficios.com> Message-ID: <20190429152803.7719-7-mathieu.desnoyers@efficios.com> Content-Type: text/plain; charset="UTF-8" Message-ID: <20190429152757.uxU97XId0AiBxHlPPSwML56rEjD6ti2cMF4HtU39y2M@z> 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 Suggested-by: Peter Zijlstra CC: Peter Zijlstra CC: Thomas Gleixner CC: Joel Fernandes CC: Catalin Marinas CC: Dave Watson CC: Will Deacon CC: Shuah Khan CC: Andi Kleen CC: linux-kselftest at vger.kernel.org CC: "H . Peter Anvin" CC: Chris Lameter CC: Russell King CC: Michael Kerrisk CC: "Paul E . McKenney" CC: Paul Turner CC: Boqun Feng CC: Josh Triplett CC: Steven Rostedt CC: Ben Maurer CC: linux-api at vger.kernel.org CC: Andy Lutomirski CC: Andrew Morton CC: Linus Torvalds --- tools/testing/selftests/rseq/rseq-x86.h | 15 +++++++++++---- 1 file 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 +/* + * 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 (%rip). */\ - ".byte 0x0f, 0x1f, 0x05\n\t" \ + /* Disassembler-friendly signature: ud1 (%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 . */ \ - ".byte 0x0f, 0x1f, 0x05\n\t" \ + /* Disassembler-friendly signature: ud1 ,%edi. */ \ + ".byte 0x0f, 0xb9, 0x3d\n\t" \ ".long " __rseq_str(RSEQ_SIG) "\n\t" \ __rseq_str(label) ":\n\t" \ teardown \ -- 2.11.0