| Message ID | 20240916120510.2017749-1-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | powerpc/atomic: Use YZ constraints for DS-form instructions | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Mon, Sep 16, 2024 at 5:05 AM Michael Ellerman <mpe@ellerman.id.au> wrote: > > The 'ld' and 'std' instructions require a 4-byte aligned displacement > because they are DS-form instructions. But the "m" asm constraint > doesn't enforce that. > > That can lead to build errors if the compiler chooses a non-aligned > displacement, as seen with GCC 14: > > /tmp/ccuSzwiR.s: Assembler messages: > /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of 4) > make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1 > > Dumping the generated assembler shows: > > ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t > > Use the YZ constraints to tell the compiler either to generate a DS-form > displacement, or use an X-form instruction, either of which prevents the > build error. > > See commit 2d43cc701b96 ("powerpc/uaccess: Fix build errors seen with > GCC 13/14") for more details on the constraint letters. > > Fixes: 9f0cbea0d8cc ("[POWERPC] Implement atomic{, 64}_{read, write}() without volatile") > Cc: stable@vger.kernel.org # v2.6.24+ > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> > Closes: https://lore.kernel.org/all/20240913125302.0a06b4c7@canb.auug.org.au > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> I'm not familiar enough with the code around the changes, but I have been able to confirm cherry-picking this resolves the build issue I'm seeing on net-next, so, FWIW, Tested-by: Mina Almasry <almasrymina@google.com>
Mina Almasry <almasrymina@google.com> writes: > On Mon, Sep 16, 2024 at 5:05 AM Michael Ellerman <mpe@ellerman.id.au> wrote: >> >> The 'ld' and 'std' instructions require a 4-byte aligned displacement >> because they are DS-form instructions. But the "m" asm constraint >> doesn't enforce that. >> >> That can lead to build errors if the compiler chooses a non-aligned >> displacement, as seen with GCC 14: >> >> /tmp/ccuSzwiR.s: Assembler messages: >> /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of 4) >> make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1 >> >> Dumping the generated assembler shows: >> >> ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t >> >> Use the YZ constraints to tell the compiler either to generate a DS-form >> displacement, or use an X-form instruction, either of which prevents the >> build error. >> >> See commit 2d43cc701b96 ("powerpc/uaccess: Fix build errors seen with >> GCC 13/14") for more details on the constraint letters. >> >> Fixes: 9f0cbea0d8cc ("[POWERPC] Implement atomic{, 64}_{read, write}() without volatile") >> Cc: stable@vger.kernel.org # v2.6.24+ >> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> >> Closes: https://lore.kernel.org/all/20240913125302.0a06b4c7@canb.auug.org.au >> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > > I'm not familiar enough with the code around the changes, but I have > been able to confirm cherry-picking this resolves the build issue I'm > seeing on net-next, so, FWIW, > > Tested-by: Mina Almasry <almasrymina@google.com> Thanks. cheers
Hi! On Mon, Sep 16, 2024 at 10:05:10PM +1000, Michael Ellerman wrote: > The 'ld' and 'std' instructions require a 4-byte aligned displacement > because they are DS-form instructions. But the "m" asm constraint > doesn't enforce that. > > That can lead to build errors if the compiler chooses a non-aligned > displacement, as seen with GCC 14: > > /tmp/ccuSzwiR.s: Assembler messages: > /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of 4) > make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1 > > Dumping the generated assembler shows: > > ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t > > Use the YZ constraints to tell the compiler either to generate a DS-form > displacement, or use an X-form instruction, either of which prevents the > build error. Great explanation text, a perfect commit! :-) > See commit 2d43cc701b96 ("powerpc/uaccess: Fix build errors seen with > GCC 13/14") for more details on the constraint letters. > > Fixes: 9f0cbea0d8cc ("[POWERPC] Implement atomic{, 64}_{read, write}() without volatile") > Cc: stable@vger.kernel.org # v2.6.24+ > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> > Closes: https://lore.kernel.org/all/20240913125302.0a06b4c7@canb.auug.org.au > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-By: Segher Boessenkool <segher@kernel.crashing.org> Segher
On Mon, 16 Sep 2024 22:05:10 +1000, Michael Ellerman wrote: > The 'ld' and 'std' instructions require a 4-byte aligned displacement > because they are DS-form instructions. But the "m" asm constraint > doesn't enforce that. > > That can lead to build errors if the compiler chooses a non-aligned > displacement, as seen with GCC 14: > > [...] Applied to powerpc/next. [1/1] powerpc/atomic: Use YZ constraints for DS-form instructions https://git.kernel.org/powerpc/c/39190ac7cff1fd15135fa8e658030d9646fdb5f2 cheers
Segher Boessenkool <segher@kernel.crashing.org> writes: > Hi! > > On Mon, Sep 16, 2024 at 10:05:10PM +1000, Michael Ellerman wrote: >> The 'ld' and 'std' instructions require a 4-byte aligned displacement >> because they are DS-form instructions. But the "m" asm constraint >> doesn't enforce that. >> >> That can lead to build errors if the compiler chooses a non-aligned >> displacement, as seen with GCC 14: >> >> /tmp/ccuSzwiR.s: Assembler messages: >> /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of 4) >> make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1 >> >> Dumping the generated assembler shows: >> >> ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t >> >> Use the YZ constraints to tell the compiler either to generate a DS-form >> displacement, or use an X-form instruction, either of which prevents the >> build error. > > Great explanation text, a perfect commit! :-) Thanks - I'm sure there's something that could be better, but I do try :) cheers
diff --git a/arch/powerpc/include/asm/asm-compat.h b/arch/powerpc/include/asm/asm-compat.h index 2bc53c646ccd..83848b534cb1 100644 --- a/arch/powerpc/include/asm/asm-compat.h +++ b/arch/powerpc/include/asm/asm-compat.h @@ -39,6 +39,12 @@ #define STDX_BE stringify_in_c(stdbrx) #endif +#ifdef CONFIG_CC_IS_CLANG +#define DS_FORM_CONSTRAINT "Z<>" +#else +#define DS_FORM_CONSTRAINT "YZ<>" +#endif + #else /* 32-bit */ /* operations for longs and pointers */ diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h index 5bf6a4d49268..d1ea554c33ed 100644 --- a/arch/powerpc/include/asm/atomic.h +++ b/arch/powerpc/include/asm/atomic.h @@ -11,6 +11,7 @@ #include <asm/cmpxchg.h> #include <asm/barrier.h> #include <asm/asm-const.h> +#include <asm/asm-compat.h> /* * Since *_return_relaxed and {cmp}xchg_relaxed are implemented with @@ -197,7 +198,7 @@ static __inline__ s64 arch_atomic64_read(const atomic64_t *v) if (IS_ENABLED(CONFIG_PPC_KERNEL_PREFIXED)) __asm__ __volatile__("ld %0,0(%1)" : "=r"(t) : "b"(&v->counter)); else - __asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m<>"(v->counter)); + __asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : DS_FORM_CONSTRAINT (v->counter)); return t; } @@ -208,7 +209,7 @@ static __inline__ void arch_atomic64_set(atomic64_t *v, s64 i) if (IS_ENABLED(CONFIG_PPC_KERNEL_PREFIXED)) __asm__ __volatile__("std %1,0(%2)" : "=m"(v->counter) : "r"(i), "b"(&v->counter)); else - __asm__ __volatile__("std%U0%X0 %1,%0" : "=m<>"(v->counter) : "r"(i)); + __asm__ __volatile__("std%U0%X0 %1,%0" : "=" DS_FORM_CONSTRAINT (v->counter) : "r"(i)); } #define ATOMIC64_OP(op, asm_op) \ diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index fd594bf6c6a9..4f5a46a77fa2 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -6,6 +6,7 @@ #include <asm/page.h> #include <asm/extable.h> #include <asm/kup.h> +#include <asm/asm-compat.h> #ifdef __powerpc64__ /* We use TASK_SIZE_USER64 as TASK_SIZE is not constant */ @@ -92,12 +93,6 @@ __pu_failed: \ : label) #endif -#ifdef CONFIG_CC_IS_CLANG -#define DS_FORM_CONSTRAINT "Z<>" -#else -#define DS_FORM_CONSTRAINT "YZ<>" -#endif - #ifdef __powerpc64__ #ifdef CONFIG_PPC_KERNEL_PREFIXED #define __put_user_asm2_goto(x, ptr, label) \
The 'ld' and 'std' instructions require a 4-byte aligned displacement because they are DS-form instructions. But the "m" asm constraint doesn't enforce that. That can lead to build errors if the compiler chooses a non-aligned displacement, as seen with GCC 14: /tmp/ccuSzwiR.s: Assembler messages: /tmp/ccuSzwiR.s:2579: Error: operand out of domain (39 is not a multiple of 4) make[5]: *** [scripts/Makefile.build:229: net/core/page_pool.o] Error 1 Dumping the generated assembler shows: ld 8,39(8) # MEM[(const struct atomic64_t *)_29].counter, t Use the YZ constraints to tell the compiler either to generate a DS-form displacement, or use an X-form instruction, either of which prevents the build error. See commit 2d43cc701b96 ("powerpc/uaccess: Fix build errors seen with GCC 13/14") for more details on the constraint letters. Fixes: 9f0cbea0d8cc ("[POWERPC] Implement atomic{, 64}_{read, write}() without volatile") Cc: stable@vger.kernel.org # v2.6.24+ Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Closes: https://lore.kernel.org/all/20240913125302.0a06b4c7@canb.auug.org.au Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/include/asm/asm-compat.h | 6 ++++++ arch/powerpc/include/asm/atomic.h | 5 +++-- arch/powerpc/include/asm/uaccess.h | 7 +------ 3 files changed, 10 insertions(+), 8 deletions(-)