linux-kernel - [PATCH v1 07/12] x86/mce: Mark mce

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Message-Id: <20211208111343.8130-8-bp@alien8.de>
Date:   Wed,  8 Dec 2021 12:13:38 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tony Luck <tony.luck@...el.com>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 07/12] x86/mce: Mark mce_panic() noinstr

From: Borislav Petkov <bp@...e.de>

And allow instrumentation inside it because it does calls to other
facilities which will not be tagged noinstr.

Fixes

  vmlinux.o: warning: objtool: do_machine_check()+0xc73: call to mce_panic() leaves .noinstr.text section

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/cpu/mce/core.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index d7fa444d6282..d81266885de3 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -266,11 +266,17 @@ static void wait_for_panic(void)
 	panic("Panicing machine check CPU died");
 }
 
-static void mce_panic(const char *msg, struct mce *final, char *exp)
+static noinstr void mce_panic(const char *msg, struct mce *final, char *exp)
 {
-	int apei_err = 0;
 	struct llist_node *pending;
 	struct mce_evt_llist *l;
+	int apei_err = 0;
+
+	/*
+	 * Allow instrumentation around external facilities usage. Not that it
+	 * matters a whole lot since the machine is going to panic anyway.
+	 */
+	instrumentation_begin();
 
 	if (!fake_panic) {
 		/*
@@ -285,7 +291,7 @@ static void mce_panic(const char *msg, struct mce *final, char *exp)
 	} else {
 		/* Don't log too much for fake panic */
 		if (atomic_inc_return(&mce_fake_panicked) > 1)
-			return;
+			goto out;
 	}
 	pending = mce_gen_pool_prepare_records();
 	/* First print corrected ones that are still unlogged */
@@ -321,6 +327,9 @@ static void mce_panic(const char *msg, struct mce *final, char *exp)
 		panic(msg);
 	} else
 		pr_emerg(HW_ERR "Fake kernel panic: %s\n", msg);
+
+out:
+	instrumentation_end();
 }
 
 /* Support code for software error injection */
-- 
2.29.2