linux-kernel - [PATCH 40/46] x86/livepatch, lto: Disable live patching with gcc LTO

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Message-Id: <20221114114344.18650-41-jirislaby@kernel.org>
Date:   Mon, 14 Nov 2022 12:43:38 +0100
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andi Kleen <andi@...stfloor.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Martin Liska <mliska@...e.cz>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 40/46] x86/livepatch, lto: Disable live patching with gcc LTO

From: Andi Kleen <andi@...stfloor.org>

It is not supported by gcc 12 so far, so it causes compiler "sorry"
messages.

Other than the compiler support, there shouldn't be any barriers for
live patching LTOed kernels, although it might be more difficult to
create patches for larger functions.

Cc: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Jiri Kosina <jikos@...nel.org>
Cc: Miroslav Benes <mbenes@...e.cz>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Joe Lawrence <joe.lawrence@...hat.com>
Cc: live-patching@...r.kernel.org
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Martin Liska <mliska@...e.cz>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 kernel/livepatch/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/livepatch/Kconfig b/kernel/livepatch/Kconfig
index 53d51ed619a3..22699adc39a6 100644
--- a/kernel/livepatch/Kconfig
+++ b/kernel/livepatch/Kconfig
@@ -12,6 +12,7 @@ config LIVEPATCH
 	depends on KALLSYMS_ALL
 	depends on HAVE_LIVEPATCH
 	depends on !TRIM_UNUSED_KSYMS
+	depends on !LTO_GCC # not supported in gcc
 	help
 	  Say Y here if you want to support kernel live patching.
 	  This option has no runtime impact until a kernel "patch"
-- 
2.38.1