Re: [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble memory as ROX

On Thu, Jun 01, 2023 at 12:30:50PM +0200, Peter Zijlstra wrote:

quoted

On Thu, Jun 01, 2023 at 01:12:56PM +0300, Mike Rapoport wrote:

quoted

+static void __init_or_module do_text_poke(void *addr, const void *opcode, size_t len)
+{
+   if (system_state < SYSTEM_RUNNING) {
+           text_poke_early(addr, opcode, len);
+   } else {
+           mutex_lock(&text_mutex);
+           text_poke(addr, opcode, len);
+           mutex_unlock(&text_mutex);
+   }
+}

So I don't much like do_text_poke(); why?

I believe the idea was to keep memcpy for early boot before the kernel
image is protected without going and adding if (is_module_text_address())
all over the place.

I think this can be used instead without updating all the call sites of
text_poke_early():

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 91057de8e6bc..f994e63e9903 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c

@@ -1458,7 +1458,7 @@ void __init_or_module text_poke_early(void *addr, const void *opcode,
                 * code cannot be running and speculative code-fetches are
                 * prevented. Just change the code.
                 */
-               memcpy(addr, opcode, len);
+               text_poke_copy(addr, opcode, len);
        } else {
                local_irq_save(flags);
                memcpy(addr, opcode, len);