[v5,02/23] x86/jump_label: Use text_poke_early() during early init

Commit Message

Nadav Amit April 26, 2019, 12:11 a.m. UTC

There is no apparent reason not to use text_poke_early() during
early-init, since no patching of code that might be on the stack is done
and only a single core is running.

This is required for the next patches that would set a temporary mm for
text poking, and this mm is only initialized after some static-keys are
enabled/disabled.

Cc: Andy Lutomirski <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Nadav Amit <[e-mail]>
Signed-off-by: Rick Edgecombe <[e-mail]>
---
 arch/x86/kernel/jump_label.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Patch

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index f99bd26bd3f1..e7d8c636b228 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -50,7 +50,12 @@  static void __ref __jump_label_transform(struct jump_entry *entry,
 	jmp.offset = jump_entry_target(entry) -
 		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 
-	if (early_boot_irqs_disabled)
+	/*
+	 * As long as only a single processor is running and the code is still
+	 * not marked as RO, text_poke_early() can be used; Checking that
+	 * system_state is SYSTEM_BOOTING guarantees it.
+	 */
+	if (system_state == SYSTEM_BOOTING)
 		poker = text_poke_early;
 
 	if (type == JUMP_LABEL_JMP) {