On Wed, May 28, 2014 at 05:33:44PM +0400, Marat Zakirov wrote:
> Here's a patch for optional Asan instrumentation of inline assembly.
>
> This version scans gimple for GIMPLE_ASMs and performs usual instrumentation
> of arguments with memory constraints ("m", "o", etc.) with fixed size.
That doesn't look right to me. The fact that some region appears in "m"
doesn't mean the inline asm actually accesses it, it could not touch it at
all, or only some part of it.
If you look e.g. at Linux kernel headers, you'll see lots of
struct __large_struct { unsigned long buf[100]; };
#define __m(x) (*(struct __large_struct __user *)(x))
...
"m" (__m(addr))
and similar cases, if Asan wants to check that the whole 100*sizeof(long)
region is accessible, it could often just have false positives, because the
inline asm really accesses just some small part of it.
Jakub
