x86/alternatives: Lockdep-enforce text_mutex in text_poke*()

text_poke() and text_poke_bp() must be called with text_mutex held.

Put proper lockdep anotation in place instead of just mentioning the
requirement in a comment.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1808280853520.25787@cbobk.fhfr.pm

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 014f214da5815d62f8f094f5e69f670c440ef69b..b9d5e7c9ef43e66c0b8d19fc0346be1779fa78d4 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -684,8 +684,6 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode,
  * It means the size must be writable atomically and the address must be aligned
  * in a way that permits an atomic write. It also makes sure we fit on a single
  * page.
- *
- * Note: Must be called under text_mutex.
  */
 void *text_poke(void *addr, const void *opcode, size_t len)
 {
@@ -700,6 +698,8 @@ void *text_poke(void *addr, const void *opcode, size_t len)
         */
        BUG_ON(!after_bootmem);
 
+       lockdep_assert_held(&text_mutex);
+
        if (!core_kernel_text((unsigned long)addr)) {
                pages[0] = vmalloc_to_page(addr);
                pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
@@ -782,8 +782,6 @@ int poke_int3_handler(struct pt_regs *regs)
  *     - replace the first byte (int3) by the first byte of
  *       replacing opcode
  *     - sync cores
- *
- * Note: must be called under text_mutex.
  */
 void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
 {
@@ -792,6 +790,9 @@ void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
        bp_int3_handler = handler;
        bp_int3_addr = (u8 *)addr + sizeof(int3);
        bp_patching_in_progress = true;
+
+       lockdep_assert_held(&text_mutex);
+
        /*
         * Corresponding read barrier in int3 notifier for making sure the
         * in_progress and handler are correctly ordered wrt. patching.