From: Uros Bizjak <ubizjak@gmail.com>
To: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Dennis Zhou <dennis@kernel.org>,
Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: [PATCH v2 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}_op()
Date: Fri, 14 Feb 2025 16:07:46 +0100 [thread overview]
Message-ID: <20250214150929.5780-1-ubizjak@gmail.com> (raw)
percpu_{,try_}cmpxchg{64,128}() macros use CALL instruction inside
asm statement in one of their alternatives. Use ALT_OUTPUT_SP()
macro to add required dependence on %esp register.
ALT_OUTPUT_SP() implements the above dependence by adding
ASM_CALL_CONSTRAINT to its arguments. This constraint should be used
for any inline asm which has a CALL instruction, otherwise the
compiler may schedule the asm before the frame pointer gets set up
by the containing function, causing objtool to print a "call without
frame pointer save/setup" warning.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
---
v2: Expand commit message with the explanation of ASM_CALL_CONSTRAINT.
---
arch/x86/include/asm/percpu.h | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index e525cd85f999..0ab991fba7de 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -350,9 +350,9 @@ do { \
\
asm qual (ALTERNATIVE("call this_cpu_cmpxchg8b_emu", \
"cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
- : [var] "+m" (__my_cpu_var(_var)), \
- "+a" (old__.low), \
- "+d" (old__.high) \
+ : ALT_OUTPUT_SP([var] "+m" (__my_cpu_var(_var)), \
+ "+a" (old__.low), \
+ "+d" (old__.high)) \
: "b" (new__.low), \
"c" (new__.high), \
"S" (&(_var)) \
@@ -381,10 +381,10 @@ do { \
asm qual (ALTERNATIVE("call this_cpu_cmpxchg8b_emu", \
"cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
CC_SET(z) \
- : CC_OUT(z) (success), \
- [var] "+m" (__my_cpu_var(_var)), \
- "+a" (old__.low), \
- "+d" (old__.high) \
+ : ALT_OUTPUT_SP(CC_OUT(z) (success), \
+ [var] "+m" (__my_cpu_var(_var)), \
+ "+a" (old__.low), \
+ "+d" (old__.high)) \
: "b" (new__.low), \
"c" (new__.high), \
"S" (&(_var)) \
@@ -421,9 +421,9 @@ do { \
\
asm qual (ALTERNATIVE("call this_cpu_cmpxchg16b_emu", \
"cmpxchg16b " __percpu_arg([var]), X86_FEATURE_CX16) \
- : [var] "+m" (__my_cpu_var(_var)), \
- "+a" (old__.low), \
- "+d" (old__.high) \
+ : ALT_OUTPUT_SP([var] "+m" (__my_cpu_var(_var)), \
+ "+a" (old__.low), \
+ "+d" (old__.high)) \
: "b" (new__.low), \
"c" (new__.high), \
"S" (&(_var)) \
@@ -452,10 +452,10 @@ do { \
asm qual (ALTERNATIVE("call this_cpu_cmpxchg16b_emu", \
"cmpxchg16b " __percpu_arg([var]), X86_FEATURE_CX16) \
CC_SET(z) \
- : CC_OUT(z) (success), \
- [var] "+m" (__my_cpu_var(_var)), \
- "+a" (old__.low), \
- "+d" (old__.high) \
+ : ALT_OUTPUT_SP(CC_OUT(z) (success), \
+ [var] "+m" (__my_cpu_var(_var)), \
+ "+a" (old__.low), \
+ "+d" (old__.high)) \
: "b" (new__.low), \
"c" (new__.high), \
"S" (&(_var)) \
--
2.42.0
next reply other threads:[~2025-02-14 15:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-14 15:07 Uros Bizjak [this message]
2025-02-14 15:07 ` [PATCH v2 2/2] x86/locking: Use asm_inline for {,try_}cmpxchg{64,128} emulations Uros Bizjak
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