On Thu, Mar 10, 2022 at 08:53:05AM +0700, Ammar Faizi wrote:
The asm constraint does not reflect that the asm statement can modify the value of @loops. But the asm statement in delay_loop() does modify the @loops.
Specifiying the wrong constraint may lead to undefined behavior, it may clobber random stuff (e.g. local variable, important temporary value in regs, etc.).
This is especially dangerous when the compiler decides to inline the function and since it doesn't know that the value gets modified, it might decide to use it from a register directly without reloading it.
Add that to the commit message pls.
Fix this by changing the constraint from "a" (as an input) to "+a" (as an input and output).
Cc: David Laight David.Laight@ACULAB.COM Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Jiri Hladky hladky.jiri@googlemail.com
All those Ccs in the commit message are not really needed - get_maintainers.pl gives the correct list already.
Cc: stable@vger.kernel.org # v2.6.27+
I don't see the need for the stable Cc. Or do you have a case where a corruption really does happen?
Fixes: e01b70ef3eb ("x86: fix bug in arch/i386/lib/delay.c file, delay_loop function")
Commit sha1 (e01b70ef3eb) needs to be at least 12 chars long:
e01b70ef3eb3 ("x86: fix bug in arch/i386/lib/delay.c file, delay_loop function")
This is best fixed by doing:
[core] abbrev = 12
in your .git/config
Signed-off-by: Ammar Faizi ammarfaizi2@gnuweeb.org
arch/x86/lib/delay.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index 65d15df6212d..0e65d00e2339 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -54,8 +54,8 @@ static void delay_loop(u64 __loops) " jnz 2b \n" "3: dec %0 \n"
: /* we don't need output */:"a" (loops)
: "+a" (loops):
Thx.