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

From: Nadav Amit <namit@vmware.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Ingo Molnar <mingo@redhat.com>
Cc: <linux-kernel@vger.kernel.org>, <x86@kernel.org>, <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nadav Amit <nadav.amit@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>, <linux_dti@icloud.com>,
	<linux-integrity@vger.kernel.org>,
	<linux-security-module@vger.kernel.org>,
	<akpm@linux-foundation.org>,
	<kernel-hardening@lists.openwall.com>, <linux-mm@kvack.org>,
	<will.deacon@arm.com>, <ard.biesheuvel@linaro.org>,
	<kristen@linux.intel.com>, <deneen.t.dock@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Nadav Amit <namit@vmware.com>, Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCH v5 02/23] x86/jump_label: Use text_poke_early() during early init
Date: Thu, 25 Apr 2019 17:11:22 -0700	[thread overview]
Message-ID: <20190426001143.4983-3-namit@vmware.com> (raw)
In-Reply-To: <20190426001143.4983-1-namit@vmware.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@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.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

