From: "tip-bot2 for Uros Bizjak" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>, Borislav Petkov <bp@suse.de>,
Sean Christopherson <seanjc@google.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/cleanups] x86/uaccess: Improve __try_cmpxchg64_user_asm() for x86_32
Date: Mon, 15 Aug 2022 19:25:33 -0000 [thread overview]
Message-ID: <166059153374.401.4511445076917339745.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20220628161612.7993-1-ubizjak@gmail.com>
The following commit has been merged into the x86/cleanups branch of tip:
Commit-ID: 4630535c64725bcd722eb59fb8d92be8db943d3d
Gitweb: https://git.kernel.org/tip/4630535c64725bcd722eb59fb8d92be8db943d3d
Author: Uros Bizjak <ubizjak@gmail.com>
AuthorDate: Tue, 28 Jun 2022 18:16:12 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 15 Aug 2022 19:18:12 +02:00
x86/uaccess: Improve __try_cmpxchg64_user_asm() for x86_32
Improve __try_cmpxcgh64_user_asm() for !CONFIG_CC_HAS_ASM_GOTO_TIED_OUTPUT
by relaxing the output register constraint from "c" to "q" constraint,
which allows the compiler to choose between %ecx or %ebx register.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220628161612.7993-1-ubizjak@gmail.com
---
arch/x86/include/asm/uaccess.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 913e593..b0583c1 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -448,7 +448,7 @@ do { \
#ifdef CONFIG_X86_32
/*
- * Unlike the normal CMPXCHG, hardcode ECX for both success/fail and error.
+ * Unlike the normal CMPXCHG, use output GPR for both success/fail and error.
* There are only six GPRs available and four (EAX, EBX, ECX, and EDX) are
* hardcoded by CMPXCHG8B, leaving only ESI and EDI. If the compiler uses
* both ESI and EDI for the memory operand, compilation will fail if the error
@@ -461,11 +461,12 @@ do { \
__typeof__(*(_ptr)) __new = (_new); \
asm volatile("\n" \
"1: " LOCK_PREFIX "cmpxchg8b %[ptr]\n" \
- "mov $0, %%ecx\n\t" \
- "setz %%cl\n" \
+ "mov $0, %[result]\n\t" \
+ "setz %b[result]\n" \
"2:\n" \
- _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %%ecx) \
- : [result]"=c" (__result), \
+ _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, \
+ %[result]) \
+ : [result] "=q" (__result), \
"+A" (__old), \
[ptr] "+m" (*_ptr) \
: "b" ((u32)__new), \
prev parent reply other threads:[~2022-08-15 21:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-28 16:16 [PATCH RESEND] x86/uaccess: Improve __try_cmpxchg64_user_asm for x86_32 Uros Bizjak
2022-08-15 19:25 ` tip-bot2 for Uros Bizjak [this message]
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