On Thu, Apr 11, 2024 at 07:05:25PM +0300, Mike Rapoport wrote:
> To populate the cache, a writable large page is allocated from vmalloc with
> VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as
> ROX.
> +static void execmem_invalidate(void *ptr, size_t size, bool writable)
> +{
> + if (execmem_info->invalidate)
> + execmem_info->invalidate(ptr, size, writable);
> + else
> + memset(ptr, 0, size);
> +}
+static void execmem_invalidate(void *ptr, size_t size, bool writeable)
+{
+ /* fill memory with INT3 instructions */
+ if (writeable)
+ memset(ptr, 0xcc, size);
+ else
+ text_poke_set(ptr, 0xcc, size);
+}
Thing is, 0xcc (aka INT3_INSN_OPCODE) is not an invalid instruction.
It raises #BP not #UD.
