void arch_livepatch_revert(const struct livepatch_func *func)
{
uint32_t *new_ptr;
unsigned int len;
new_ptr = func->old_addr - (void *)_start + vmap_of_xen_text;
len = livepatch_insn_len(func);
memcpy(new_ptr, func->opaque, len);
clean_and_invalidate_dcache_va_range(new_ptr, len);
}
void arch_livepatch_apply(struct livepatch_func *func)
{
uint32_t insn;
uint32_t *new_ptr;
unsigned int i, len;
BUILD_BUG_ON(ARCH_PATCH_INSN_SIZE > sizeof(func->opaque));
BUILD_BUG_ON(ARCH_PATCH_INSN_SIZE != sizeof(insn));
ASSERT(vmap_of_xen_text);
len = livepatch_insn_len(func);
if ( !len )
return;
/* Save old ones. */
memcpy(func->opaque, func->old_addr, len);
if ( func->new_addr )
{
s32 delta;
/*
* PC is current address (old_addr) + 8 bytes. The semantics for a
* unconditional branch is to jump to PC + imm32 (offset).
*
* ARM DDI 0406C.c, see A2.3 (pg 45) and A8.8.18 pg (pg 334,335)
*
*/
delta = (s32)func->new_addr - (s32)(func->old_addr + 8);
/* The arch_livepatch_symbol_ok should have caught it. */
ASSERT(delta >= -(s32)ARCH_LIVEPATCH_RANGE ||
delta < (s32)ARCH_LIVEPATCH_RANGE);
/* CPU shifts by two (left) when decoding, so we shift right by two. */
delta = delta >> 2;
/* Lets not modify the cond. */
delta &= 0x00FFFFFF;
insn = 0xea000000 | delta;
}
