| Message ID | 20220107232746.1540130-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | arm64: atomics: Dereference matching size | expand |
On Sat, 8 Jan 2022 at 00:28, Kees Cook <keescook@chromium.org> wrote: > > When building with -Warray-bounds (which is desired to be enabled > globally), the following warning is generated: > > In file included from ./arch/arm64/include/asm/lse.h:16, > from ./arch/arm64/include/asm/cmpxchg.h:14, > from ./arch/arm64/include/asm/atomic.h:16, > from ./include/linux/atomic.h:7, > from ./include/asm-generic/bitops/atomic.h:5, > from ./arch/arm64/include/asm/bitops.h:25, > from ./include/linux/bitops.h:33, > from ./include/linux/kernel.h:22, > from kernel/printk/printk.c:22: > ./arch/arm64/include/asm/atomic_lse.h:247:9: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'atomic_t[1]' [-Warray-bounds] > 247 | asm volatile( \ > | ^~~ > ./arch/arm64/include/asm/atomic_lse.h:266:1: note: in expansion of macro '__CMPXCHG_CASE' > 266 | __CMPXCHG_CASE(w, , acq_, 32, a, "memory") > | ^~~~~~~~~~~~~~ > kernel/printk/printk.c:3606:17: note: while referencing 'printk_cpulock_owner' > 3606 | static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1); > | ^~~~~~~~~~~~~~~~~~~~ > > This is due to the compiler seeing an unsigned long * cast against > something (atomic_t) that is int sized. Replace the cast with the > matching size cast. This results in no change in binary output. > > Cc: Will Deacon <will@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Ard Biesheuvel <ardb@kernel.org> > --- > arch/arm64/include/asm/atomic_lse.h | 2 +- > arch/arm64/include/asm/cmpxchg.h | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h > index d955ade5df7c..5d460f6b7675 100644 > --- a/arch/arm64/include/asm/atomic_lse.h > +++ b/arch/arm64/include/asm/atomic_lse.h > @@ -249,7 +249,7 @@ __lse__cmpxchg_case_##name##sz(volatile void *ptr, \ > " mov %" #w "[tmp], %" #w "[old]\n" \ > " cas" #mb #sfx "\t%" #w "[tmp], %" #w "[new], %[v]\n" \ > " mov %" #w "[ret], %" #w "[tmp]" \ > - : [ret] "+r" (x0), [v] "+Q" (*(unsigned long *)ptr), \ > + : [ret] "+r" (x0), [v] "+Q" (*(u##sz *)ptr), \ > [tmp] "=&r" (tmp) \ > : [old] "r" (x1), [new] "r" (x2) \ > : cl); \ > diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h > index f9bef42c1411..497acf134d99 100644 > --- a/arch/arm64/include/asm/cmpxchg.h > +++ b/arch/arm64/include/asm/cmpxchg.h > @@ -243,7 +243,7 @@ static inline void __cmpwait_case_##sz(volatile void *ptr, \ > " cbnz %" #w "[tmp], 1f\n" \ > " wfe\n" \ > "1:" \ > - : [tmp] "=&r" (tmp), [v] "+Q" (*(unsigned long *)ptr) \ > + : [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr) \ > : [val] "r" (val)); \ > } > > -- > 2.30.2 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Hi Kees, On Fri, Jan 07, 2022 at 03:27:46PM -0800, Kees Cook wrote: > When building with -Warray-bounds (which is desired to be enabled > globally), the following warning is generated: > > In file included from ./arch/arm64/include/asm/lse.h:16, > from ./arch/arm64/include/asm/cmpxchg.h:14, > from ./arch/arm64/include/asm/atomic.h:16, > from ./include/linux/atomic.h:7, > from ./include/asm-generic/bitops/atomic.h:5, > from ./arch/arm64/include/asm/bitops.h:25, > from ./include/linux/bitops.h:33, > from ./include/linux/kernel.h:22, > from kernel/printk/printk.c:22: > ./arch/arm64/include/asm/atomic_lse.h:247:9: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'atomic_t[1]' [-Warray-bounds] > 247 | asm volatile( \ > | ^~~ > ./arch/arm64/include/asm/atomic_lse.h:266:1: note: in expansion of macro '__CMPXCHG_CASE' > 266 | __CMPXCHG_CASE(w, , acq_, 32, a, "memory") > | ^~~~~~~~~~~~~~ > kernel/printk/printk.c:3606:17: note: while referencing 'printk_cpulock_owner' > 3606 | static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1); > | ^~~~~~~~~~~~~~~~~~~~ > > This is due to the compiler seeing an unsigned long * cast against > something (atomic_t) that is int sized. Replace the cast with the > matching size cast. This results in no change in binary output. Just to check, I assume both GCC and Clang are happy with this applied? I recall that (historically at least) clang would warn about size mismatches for inline assembly and would sometimes require more care. I don't see anythign for which that would matter, but I just want to check. > Cc: Will Deacon <will@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > arch/arm64/include/asm/atomic_lse.h | 2 +- > arch/arm64/include/asm/cmpxchg.h | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h > index d955ade5df7c..5d460f6b7675 100644 > --- a/arch/arm64/include/asm/atomic_lse.h > +++ b/arch/arm64/include/asm/atomic_lse.h > @@ -249,7 +249,7 @@ __lse__cmpxchg_case_##name##sz(volatile void *ptr, \ > " mov %" #w "[tmp], %" #w "[old]\n" \ > " cas" #mb #sfx "\t%" #w "[tmp], %" #w "[new], %[v]\n" \ > " mov %" #w "[ret], %" #w "[tmp]" \ > - : [ret] "+r" (x0), [v] "+Q" (*(unsigned long *)ptr), \ > + : [ret] "+r" (x0), [v] "+Q" (*(u##sz *)ptr), \ > [tmp] "=&r" (tmp) \ > : [old] "r" (x1), [new] "r" (x2) \ > : cl); \ It might be worth nothing that __ll_sc__cmpxchg_case_##name##sz already uses the same constraint: [v] "+Q" (*(u##sz *)ptr ... since that explains why we only need to update the LSE form and not the LL/SC form, and indicates that this is unlikely to be problematic. Either way: Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks, Mark. > diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h > index f9bef42c1411..497acf134d99 100644 > --- a/arch/arm64/include/asm/cmpxchg.h > +++ b/arch/arm64/include/asm/cmpxchg.h > @@ -243,7 +243,7 @@ static inline void __cmpwait_case_##sz(volatile void *ptr, \ > " cbnz %" #w "[tmp], 1f\n" \ > " wfe\n" \ > "1:" \ > - : [tmp] "=&r" (tmp), [v] "+Q" (*(unsigned long *)ptr) \ > + : [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr) \ > : [val] "r" (val)); \ > } > > -- > 2.30.2 >
On Mon, Jan 10, 2022 at 10:27:59AM +0000, Mark Rutland wrote: > Hi Kees, > > On Fri, Jan 07, 2022 at 03:27:46PM -0800, Kees Cook wrote: > > When building with -Warray-bounds (which is desired to be enabled > > globally), the following warning is generated: > > > > In file included from ./arch/arm64/include/asm/lse.h:16, > > from ./arch/arm64/include/asm/cmpxchg.h:14, > > from ./arch/arm64/include/asm/atomic.h:16, > > from ./include/linux/atomic.h:7, > > from ./include/asm-generic/bitops/atomic.h:5, > > from ./arch/arm64/include/asm/bitops.h:25, > > from ./include/linux/bitops.h:33, > > from ./include/linux/kernel.h:22, > > from kernel/printk/printk.c:22: > > ./arch/arm64/include/asm/atomic_lse.h:247:9: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'atomic_t[1]' [-Warray-bounds] > > 247 | asm volatile( \ > > | ^~~ > > ./arch/arm64/include/asm/atomic_lse.h:266:1: note: in expansion of macro '__CMPXCHG_CASE' > > 266 | __CMPXCHG_CASE(w, , acq_, 32, a, "memory") > > | ^~~~~~~~~~~~~~ > > kernel/printk/printk.c:3606:17: note: while referencing 'printk_cpulock_owner' > > 3606 | static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1); > > | ^~~~~~~~~~~~~~~~~~~~ > > > > This is due to the compiler seeing an unsigned long * cast against > > something (atomic_t) that is int sized. Replace the cast with the > > matching size cast. This results in no change in binary output. > > Just to check, I assume both GCC and Clang are happy with this applied? > > I recall that (historically at least) clang would warn about size mismatches > for inline assembly and would sometimes require more care. I don't see anythign > for which that would matter, but I just want to check. Yup, Clang is happy with this AFAICT. > > > Cc: Will Deacon <will@kernel.org> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Boqun Feng <boqun.feng@gmail.com> > > Cc: Catalin Marinas <catalin.marinas@arm.com> > > Cc: linux-arm-kernel@lists.infradead.org > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > arch/arm64/include/asm/atomic_lse.h | 2 +- > > arch/arm64/include/asm/cmpxchg.h | 2 +- > > 2 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h > > index d955ade5df7c..5d460f6b7675 100644 > > --- a/arch/arm64/include/asm/atomic_lse.h > > +++ b/arch/arm64/include/asm/atomic_lse.h > > @@ -249,7 +249,7 @@ __lse__cmpxchg_case_##name##sz(volatile void *ptr, \ > > " mov %" #w "[tmp], %" #w "[old]\n" \ > > " cas" #mb #sfx "\t%" #w "[tmp], %" #w "[new], %[v]\n" \ > > " mov %" #w "[ret], %" #w "[tmp]" \ > > - : [ret] "+r" (x0), [v] "+Q" (*(unsigned long *)ptr), \ > > + : [ret] "+r" (x0), [v] "+Q" (*(u##sz *)ptr), \ > > [tmp] "=&r" (tmp) \ > > : [old] "r" (x1), [new] "r" (x2) \ > > : cl); \ > > It might be worth nothing that __ll_sc__cmpxchg_case_##name##sz already uses > the same constraint: > > [v] "+Q" (*(u##sz *)ptr > > ... since that explains why we only need to update the LSE form and not the > LL/SC form, and indicates that this is unlikely to be problematic. Good idea, I'll note that in a v2. > > Either way: > > Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks! -Kees > > Thanks, > Mark. > > > diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h > > index f9bef42c1411..497acf134d99 100644 > > --- a/arch/arm64/include/asm/cmpxchg.h > > +++ b/arch/arm64/include/asm/cmpxchg.h > > @@ -243,7 +243,7 @@ static inline void __cmpwait_case_##sz(volatile void *ptr, \ > > " cbnz %" #w "[tmp], 1f\n" \ > > " wfe\n" \ > > "1:" \ > > - : [tmp] "=&r" (tmp), [v] "+Q" (*(unsigned long *)ptr) \ > > + : [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr) \ > > : [val] "r" (val)); \ > > } > > > > -- > > 2.30.2 > >
diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h index d955ade5df7c..5d460f6b7675 100644 --- a/arch/arm64/include/asm/atomic_lse.h +++ b/arch/arm64/include/asm/atomic_lse.h @@ -249,7 +249,7 @@ __lse__cmpxchg_case_##name##sz(volatile void *ptr, \ " mov %" #w "[tmp], %" #w "[old]\n" \ " cas" #mb #sfx "\t%" #w "[tmp], %" #w "[new], %[v]\n" \ " mov %" #w "[ret], %" #w "[tmp]" \ - : [ret] "+r" (x0), [v] "+Q" (*(unsigned long *)ptr), \ + : [ret] "+r" (x0), [v] "+Q" (*(u##sz *)ptr), \ [tmp] "=&r" (tmp) \ : [old] "r" (x1), [new] "r" (x2) \ : cl); \ diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index f9bef42c1411..497acf134d99 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -243,7 +243,7 @@ static inline void __cmpwait_case_##sz(volatile void *ptr, \ " cbnz %" #w "[tmp], 1f\n" \ " wfe\n" \ "1:" \ - : [tmp] "=&r" (tmp), [v] "+Q" (*(unsigned long *)ptr) \ + : [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr) \ : [val] "r" (val)); \ }
When building with -Warray-bounds (which is desired to be enabled globally), the following warning is generated: In file included from ./arch/arm64/include/asm/lse.h:16, from ./arch/arm64/include/asm/cmpxchg.h:14, from ./arch/arm64/include/asm/atomic.h:16, from ./include/linux/atomic.h:7, from ./include/asm-generic/bitops/atomic.h:5, from ./arch/arm64/include/asm/bitops.h:25, from ./include/linux/bitops.h:33, from ./include/linux/kernel.h:22, from kernel/printk/printk.c:22: ./arch/arm64/include/asm/atomic_lse.h:247:9: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'atomic_t[1]' [-Warray-bounds] 247 | asm volatile( \ | ^~~ ./arch/arm64/include/asm/atomic_lse.h:266:1: note: in expansion of macro '__CMPXCHG_CASE' 266 | __CMPXCHG_CASE(w, , acq_, 32, a, "memory") | ^~~~~~~~~~~~~~ kernel/printk/printk.c:3606:17: note: while referencing 'printk_cpulock_owner' 3606 | static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1); | ^~~~~~~~~~~~~~~~~~~~ This is due to the compiler seeing an unsigned long * cast against something (atomic_t) that is int sized. Replace the cast with the matching size cast. This results in no change in binary output. Cc: Will Deacon <will@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm64/include/asm/atomic_lse.h | 2 +- arch/arm64/include/asm/cmpxchg.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)