Re: [PATCH] arm64: lib: use C string functions with KASAN enabled.

Andrey Ryabinin
2018-09-07T15:48:08Z

On 09/07/2018 05:56 PM, Will Deacon wrote:
> On Thu, Sep 06, 2018 at 08:05:33PM +0300, Andrey Ryabinin wrote:
>> ARM64 has asm implementations of memchr(), memcmp(), str[r]chr(),
>> str[n]cmp(), str[n]len(). KASAN don't see memory accesses in asm
>> code, thus it can potentially miss many bugs.
>>
>> Ifdef out __HAVE_ARCH_* defines of these functions when KASAN is
>> enabled, so the generic implementations from lib/string.c will be used.
>>
>> Declare asm functions as weak instead of removing them because they
>> still can be used by efistub.
>
> I don't understand this bit: efistub uses the __pi_ prefixed versions of the
> routines, so why do we need to declare them as weak?

Weak needed because we can't have two non-weak functions with the same name.

Alternative approach would be to never use e.g. "strlen" name for asm implementation of strlen() under CONFIG_KASAN=y.
But that would require adding some special ENDPIPROC_KASAN() macro since we want __pi_strlen() to point
to the asm_strlen().

Using weak seems like a way better solution to me.

>
> Will
>