/*
* Replace instructions with better alternatives for this CPU type.
* This runs before SMP is initialized to avoid SMP problems with
* self modifying code. This implies that asymmetric systems where
* APs have less capabilities than the boot processor are not handled.
* Tough. Make sure you disable such features by hand.
*/
static void __init apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
struct alt_instr *a;
u8 *instr, *replacement;
u8 insnbuf[MAX_PATCH_LEN];
ASSERT(!local_irq_is_enabled());
printk(KERN_INFO "alt table %p -> %p\n", start, end);
/*
* The scan order should be from start to end. A later scanned
* alternative code can overwrite a previous scanned alternative code.
* Some kernel functions (e.g. memcpy, memset, etc) use this order to
* patch code.
*
* So be careful if you want to change the scan order to any other
* order.
*/
for ( a = start; a < end; a++ )
{
instr = (u8 *)&a->instr_offset + a->instr_offset;
replacement = (u8 *)&a->repl_offset + a->repl_offset;
BUG_ON(a->replacementlen > a->instrlen);
BUG_ON(a->instrlen > sizeof(insnbuf));
BUG_ON(a->cpuid >= NCAPINTS * 32);
if ( !boot_cpu_has(a->cpuid) )
continue;
memcpy(insnbuf, replacement, a->replacementlen);
/* 0xe8/0xe9 are relative branches; fix the offset. */
if ( (*insnbuf & 0xfe) == 0xe8 && a->replacementlen == 5 )
*(s32 *)(insnbuf + 1) += replacement - instr;
add_nops(insnbuf + a->replacementlen,
a->instrlen - a->replacementlen);
text_poke_early(instr, insnbuf, a->instrlen);
}
}
void arch_jump_label_text_poke_early(jump_label_t addr)
{
text_poke_early((void *)addr, ideal_nops[NOP_ATOMIC5],
JUMP_LABEL_NOP_SIZE);
}
