On 02/06/2010 01:36 AM, Borislav Petkov wrote: > >> c) You call a C function, but you don't clobber the set of registers >> that a C function would clobber. You either need to put the function in >> an assembly wrapper (which is better in the long run), or clobber the >> full set of registers that is clobbered by a C function (which is better >> in the short term) -- which is eax, edx, ecx on 32 bits, but rax, rdi, >> esi, rdx, rcx, r8, r9, r10, r11 on 64 bits. > > I think you mean rsi instead of esi here. > > Well, the example Brian pointed me to - __mutex_fastpath_lock - lists > the full set of clobbered registers. Please elaborate on the assembly > wrapper for the function, wouldn't I need to list all the clobbered > registers there too or am I missing something? > The notion there would be that you do push/pop in the assembly wrapper. >> d) On the other hand, you do *not* need a "memory" clobber. > > Right, in this case we have all non-barrier like inlines so no memory > clobber, according to the comment above alternative() macro. OK, I'm missing something here. A few more notions: a. This is exactly the kind of code where you don't want to put "volatile" on your asm statement, because it's a pure compute. b. It is really rather pointless to go through the whole alternatives work if you are then going to put it inside a function which isn't an inline ... -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
