On 02/22/2010 10:49 AM, Borislav Petkov wrote: >> >> Just a note: this still means rdi is clobbered on x86-64, which is >> probably fine, but needs to be recorded as such. Since gcc doesn't >> support clobbers for registers used as operands (sigh), you have to >> create a dummy output and assign it a "=D" constraint. >> >> I don't know if gcc would handle -fcall-saved-rdi here... and if so, how >> reliably. > > Ok, from looking at kernel/sched.s output it looks like it saves rdi > content over the alternative where needed. I'll do some more testing > just to make sure. > No, you can't rely on behavioral observation. A different version of gcc could behave differently. We need to make sure we tell gcc what the requirements actually are, as opposed to thinking we can just fix them. +#define POPCNT ".byte 0xf3\n\t.byte 0x48\n\t.byte 0x0f\n\t.byte 0xb8\n\t.byte 0xc7" BTW, this can be written: #define POPCNT ".byte 0xf3,0x48,0x0f,0xb8,0xc7" -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
