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Date: Fri, 26 Apr 2019 16:22:41 -0700
From: nadav.amit@...il.com
To: Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>,
	Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	x86@...nel.org,
	hpa@...or.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	linux_dti@...oud.com,
	linux-integrity@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	akpm@...ux-foundation.org,
	kernel-hardening@...ts.openwall.com,
	linux-mm@...ck.org,
	will.deacon@....com,
	ard.biesheuvel@...aro.org,
	kristen@...ux.intel.com,
	deneen.t.dock@...el.com,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Nadav Amit <namit@...are.com>,
	Kees Cook <keescook@...omium.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH v6 02/24] x86/jump_label: Use text_poke_early() during early init

From: Nadav Amit <namit@...are.com>

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 <luto@...nel.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Nadav Amit <namit@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
 arch/x86/kernel/jump_label.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

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) {
-- 
2.17.1

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