| Message ID | 20210211025149.3544593-2-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM: kprobes: asm warning fixes and UAL conversion | expand |
On Thu, 11 Feb 2021 at 03:52, Nick Desaulniers <ndesaulniers@google.com> wrote: > > GNU as warns twice for this file: > Warning: using r15 results in unpredictable behaviour > > via the Arm ARM: > K1.1.1 Overview of the constraints on Armv7 UNPREDICTABLE behaviors > > The term UNPREDICTABLE describes a number of cases where the > architecture has a feature that software must not use. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1271 > Link: https://reviews.llvm.org/D95586 > Reported-by: kernelci.org bot <bot@kernelci.org> > Suggested-by: Peter Smith <peter.smith@arm.com> > Suggested-by: Renato Golin <rengolin@systemcall.eu> > Suggested-by: David Spickett <david.spickett@linaro.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> But can we add a bit more context to the commit log, please? It is not obvious to the casual reader why it is OK to emit UNPREDICTABLE opcodes, i.e., that these are selftests that aim to ensure that kprobe never attempts to replace the opcodes in question with a probe, but that they are not actually executed, or expected to occur in real code. > --- > arch/arm/probes/kprobes/test-arm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/probes/kprobes/test-arm.c b/arch/arm/probes/kprobes/test-arm.c > index 977369f1aa48..2543106a203e 100644 > --- a/arch/arm/probes/kprobes/test-arm.c > +++ b/arch/arm/probes/kprobes/test-arm.c > @@ -166,10 +166,10 @@ void kprobe_arm_test_cases(void) > > /* Data-processing with PC as a target and status registers updated */ > TEST_UNSUPPORTED("movs pc, r1") > - TEST_UNSUPPORTED("movs pc, r1, lsl r2") > + TEST_UNSUPPORTED(__inst_arm(0xe1b0f211) " @movs pc, r1, lsl r2") > TEST_UNSUPPORTED("movs pc, #0x10000") > TEST_UNSUPPORTED("adds pc, lr, r1") > - TEST_UNSUPPORTED("adds pc, lr, r1, lsl r2") > + TEST_UNSUPPORTED(__inst_arm(0xe09ef211) " @adds pc, lr, r1, lsl r2") > TEST_UNSUPPORTED("adds pc, lr, #4") > > /* Data-processing with SP as target */ > -- > 2.30.0.478.g8a0d178c01-goog >
On Thu, Feb 11, 2021 at 12:15 AM Ard Biesheuvel <ardb@kernel.org> wrote: > > On Thu, 11 Feb 2021 at 03:52, Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > GNU as warns twice for this file: > > Warning: using r15 results in unpredictable behaviour > > > > via the Arm ARM: > > K1.1.1 Overview of the constraints on Armv7 UNPREDICTABLE behaviors > > > > The term UNPREDICTABLE describes a number of cases where the > > architecture has a feature that software must not use. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1271 > > Link: https://reviews.llvm.org/D95586 > > Reported-by: kernelci.org bot <bot@kernelci.org> > > Suggested-by: Peter Smith <peter.smith@arm.com> > > Suggested-by: Renato Golin <rengolin@systemcall.eu> > > Suggested-by: David Spickett <david.spickett@linaro.org> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > > Acked-by: Ard Biesheuvel <ardb@kernel.org> > > But can we add a bit more context to the commit log, please? It is not Sure, that's a good idea. > obvious to the casual reader why it is OK to emit UNPREDICTABLE > opcodes, i.e., that these are selftests that aim to ensure that kprobe > never attempts to replace the opcodes in question with a probe, but > that they are not actually executed, or expected to occur in real > code. I'll add: Ard notes: These are selftests that aim to ensure that kprobe never attempts to replace the opcodes in question with a probe, but they are not actually executed, or expected to occur in real code. to the commit message, when submitting to RMK's queue. Thanks for taking a look and the feedback. > > > --- > > arch/arm/probes/kprobes/test-arm.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm/probes/kprobes/test-arm.c b/arch/arm/probes/kprobes/test-arm.c > > index 977369f1aa48..2543106a203e 100644 > > --- a/arch/arm/probes/kprobes/test-arm.c > > +++ b/arch/arm/probes/kprobes/test-arm.c > > @@ -166,10 +166,10 @@ void kprobe_arm_test_cases(void) > > > > /* Data-processing with PC as a target and status registers updated */ > > TEST_UNSUPPORTED("movs pc, r1") > > - TEST_UNSUPPORTED("movs pc, r1, lsl r2") > > + TEST_UNSUPPORTED(__inst_arm(0xe1b0f211) " @movs pc, r1, lsl r2") > > TEST_UNSUPPORTED("movs pc, #0x10000") > > TEST_UNSUPPORTED("adds pc, lr, r1") > > - TEST_UNSUPPORTED("adds pc, lr, r1, lsl r2") > > + TEST_UNSUPPORTED(__inst_arm(0xe09ef211) " @adds pc, lr, r1, lsl r2") > > TEST_UNSUPPORTED("adds pc, lr, #4") > > > > /* Data-processing with SP as target */ > > -- > > 2.30.0.478.g8a0d178c01-goog > >
diff --git a/arch/arm/probes/kprobes/test-arm.c b/arch/arm/probes/kprobes/test-arm.c index 977369f1aa48..2543106a203e 100644 --- a/arch/arm/probes/kprobes/test-arm.c +++ b/arch/arm/probes/kprobes/test-arm.c @@ -166,10 +166,10 @@ void kprobe_arm_test_cases(void) /* Data-processing with PC as a target and status registers updated */ TEST_UNSUPPORTED("movs pc, r1") - TEST_UNSUPPORTED("movs pc, r1, lsl r2") + TEST_UNSUPPORTED(__inst_arm(0xe1b0f211) " @movs pc, r1, lsl r2") TEST_UNSUPPORTED("movs pc, #0x10000") TEST_UNSUPPORTED("adds pc, lr, r1") - TEST_UNSUPPORTED("adds pc, lr, r1, lsl r2") + TEST_UNSUPPORTED(__inst_arm(0xe09ef211) " @adds pc, lr, r1, lsl r2") TEST_UNSUPPORTED("adds pc, lr, #4") /* Data-processing with SP as target */
GNU as warns twice for this file: Warning: using r15 results in unpredictable behaviour via the Arm ARM: K1.1.1 Overview of the constraints on Armv7 UNPREDICTABLE behaviors The term UNPREDICTABLE describes a number of cases where the architecture has a feature that software must not use. Link: https://github.com/ClangBuiltLinux/linux/issues/1271 Link: https://reviews.llvm.org/D95586 Reported-by: kernelci.org bot <bot@kernelci.org> Suggested-by: Peter Smith <peter.smith@arm.com> Suggested-by: Renato Golin <rengolin@systemcall.eu> Suggested-by: David Spickett <david.spickett@linaro.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- arch/arm/probes/kprobes/test-arm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)