From: Jisheng Zhang Date: Thu, 6 Oct 2022 07:55:42 +0000 (+0800) Subject: arm64: alternative: constify alternative_has_feature_* argument X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b9024f87d63fde052daa8687d16a23ea0f894bb0;p=linux.git arm64: alternative: constify alternative_has_feature_* argument Inspired by x86 commit 864b435514b2("x86/jump_label: Mark arguments as const to satisfy asm constraints"), constify alternative_has_feature_* argument to satisfy asm constraints. And Steven in [1] also pointed out that "The "i" constraint needs to be a constant." Tested with building a simple external kernel module with "O0". Before the patch, got similar gcc warnings and errors as below: In file included from : In function ‘alternative_has_feature_likely’, inlined from ‘system_capabilities_finalized’ at arch/arm64/include/asm/cpufeature.h:440:9, inlined from ‘arm64_preempt_schedule_irq’ at arch/arm64/kernel/entry-common.c:264:6: include/linux/compiler_types.h:285:33: warning: ‘asm’ operand 0 probably does not match constraints 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ arch/arm64/include/asm/alternative-macros.h:232:9: note: in expansion of macro ‘asm_volatile_goto’ 232 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ include/linux/compiler_types.h:285:33: error: impossible constraint in ‘asm’ 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ arch/arm64/include/asm/alternative-macros.h:232:9: note: in expansion of macro ‘asm_volatile_goto’ 232 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ After the patch, the simple external test kernel module is built fine with "-O0". [1]https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/ Signed-off-by: Jisheng Zhang Link: https://lore.kernel.org/r/20221006075542.2658-3-jszhang@kernel.org Signed-off-by: Will Deacon --- diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h index 3622e9f4fb442..bdf1f6bcd0103 100644 --- a/arch/arm64/include/asm/alternative-macros.h +++ b/arch/arm64/include/asm/alternative-macros.h @@ -224,7 +224,7 @@ alternative_endif #include static __always_inline bool -alternative_has_feature_likely(unsigned long feature) +alternative_has_feature_likely(const unsigned long feature) { compiletime_assert(feature < ARM64_NCAPS, "feature must be < ARM64_NCAPS"); @@ -242,7 +242,7 @@ l_no: } static __always_inline bool -alternative_has_feature_unlikely(unsigned long feature) +alternative_has_feature_unlikely(const unsigned long feature) { compiletime_assert(feature < ARM64_NCAPS, "feature must be < ARM64_NCAPS");