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x86/delay: Fix the wrong asm constraint in delay_loop()
[ Upstream commitb86eb74098
] The asm constraint does not reflect the fact that the asm statement can modify the value of the local variable loops. Which it does. Specifying 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. Change the constraint to "+a" to denote that the first argument is an input and an output argument. [ bp: Fix typo, massage commit message. ] Fixes:e01b70ef3e
("x86: fix bug in arch/i386/lib/delay.c file, delay_loop function") Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20220329104705.65256-2-ammarfaizi2@gnuweeb.org Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 2 deletions
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@ -54,8 +54,8 @@ static void delay_loop(u64 __loops)
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" jnz 2b \n"
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"3: dec %0 \n"
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: /* we don't need output */
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:"a" (loops)
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: "+a" (loops)
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:
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);
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}
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