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SubjectRe: [PATCH] x86,boot: standardize strcmp()
On Tue, Mar 17, 2015 at 08:46:08AM +0100, Ingo Molnar wrote:
> I'd also add the following to the changelog:

Added:

---
From: Arjun Sreedharan <arjun024@gmail.com>
Date: Mon, 16 Mar 2015 21:07:47 +0530
Subject: [PATCH] x86/boot: Standardize strcmp()

strcmp() is always expected to return 0 when arguments are equal,
negative when its first argument @str1 is less than its second argument
@str2 and a positive value otherwise. Previously strcmp("a", "b")
returned 1. Now it gives -1, as it is supposed to.

Until now this bug never triggered, because all uses for strcmp() in the
boot code tested for nonzero:

triton:~/tip> git grep strcmp arch/x86/boot/
arch/x86/boot/boot.h:int strcmp(const char *str1, const char *str2);
arch/x86/boot/edd.c: if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
arch/x86/boot/edd.c: else if (!strcmp(eddarg, "off"))
arch/x86/boot/edd.c: else if (!strcmp(eddarg, "on"))

should in the future strcmp() be used in a comparative way in the boot
code, it might have led to (not so subtle) bugs.

Signed-off-by: Arjun Sreedharan <arjun024@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1426520267-1803-1-git-send-email-arjun024@gmail.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/boot/string.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index 493f3fd9f139..318b8465d302 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -30,7 +30,7 @@ int strcmp(const char *str1, const char *str2)
int delta = 0;

while (*s1 || *s2) {
- delta = *s2 - *s1;
+ delta = *s1 - *s2;
if (delta)
return delta;
s1++;
--
2.3.3
--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


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