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Message-Id: <20221223172338.3813186-1-ammarfaizi2@gnuweeb.org>
Date: Sat, 24 Dec 2022 00:23:38 +0700
From: Ammar Faizi <ammarfaizi2@...weeb.org>
To: x86 Mailing List <x86@...nel.org>
Cc: Ammar Faizi <ammarfaizi2@...weeb.org>,
Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux User-Mode Mailing List <linux-um@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>
Subject: [PATCH v1] x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list
From: Ammar Faizi <ammarfaizi2@...weeb.org>
The 'syscall' instruction clobbers '%rcx' and '%r11', but they are not
listed in the inline Assembly that performs the syscall instruction.
No real bug is found. It wasn't buggy by luck because '%rcx' and '%r11'
are caller-saved registers, and not used in the functions, and the
functions are never inlined.
Add them to the clobber list for code correctness.
Fixes: f1c2bb8b9964ed31de988910f8b1cfb586d30091 ("um: implement a x86_64 vDSO")
Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
---
arch/x86/um/vdso/um_vdso.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/x86/um/vdso/um_vdso.c b/arch/x86/um/vdso/um_vdso.c
index 2112b8d14668..ff0f3b4b6c45 100644
--- a/arch/x86/um/vdso/um_vdso.c
+++ b/arch/x86/um/vdso/um_vdso.c
@@ -17,8 +17,10 @@ int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
{
long ret;
- asm("syscall" : "=a" (ret) :
- "0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory");
+ asm("syscall"
+ : "=a" (ret)
+ : "0" (__NR_clock_gettime), "D" (clock), "S" (ts)
+ : "rcx", "r11", "memory");
return ret;
}
@@ -29,8 +31,10 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
long ret;
- asm("syscall" : "=a" (ret) :
- "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
+ asm("syscall"
+ : "=a" (ret)
+ : "0" (__NR_gettimeofday), "D" (tv), "S" (tz)
+ : "rcx", "r11", "memory");
return ret;
}
base-commit: 8395ae05cb5a2e31d36106e8c85efa11cda849be
--
Ammar Faizi
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