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Date:   Thu,  9 Sep 2021 12:49:25 +0200
Message-Id: <20210909104925.809674-1-elver@google.com>
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Subject: [PATCH] kasan: double -Wframe-larger-than threshold if KASAN
From:   Marco Elver <elver@google.com>
To:     elver@google.com, Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        Arnd Bergmann <arnd@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Aleksandr Nogikh <nogikh@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Taras Madan <tarasmadan@google.com>, linux-mm@kvack.org,
        llvm@lists.linux.dev
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

All architectures at least double stack size when using one of the KASAN
software modes that rely on compiler instrumentation.

Until now, warnings emitted by -Wframe-larger-than could easily be
ignored, as we would still get a working kernel.

However, with the introduction of -Werror (CONFIG_WERROR=y), it makes
sense to at least double the -Wframe-larger-than threshold for
software-based KASAN modes to reflect the already increased stack sizes
when building a kernel with KASAN enabled.

Link: https://lkml.kernel.org/r/YTbOs13waorzamZ6@Ryzen-9-3900X.localdomain
Signed-off-by: Marco Elver <elver@google.com>
---
 lib/Kconfig.debug | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ed4a31e34098..2055bbb6724a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -345,6 +345,8 @@ endif # DEBUG_INFO
 config FRAME_WARN
 	int "Warn for stack frames larger than"
 	range 0 8192
+	default 4096 if 64BIT && (KASAN_GENERIC || KASAN_SW_TAGS)
+	default 2048 if !64BIT && (KASAN_GENERIC || KASAN_SW_TAGS)
 	default 2048 if GCC_PLUGIN_LATENT_ENTROPY
 	default 1536 if (!64BIT && PARISC)
 	default 1024 if (!64BIT && !PARISC)
-- 
2.33.0.153.gba50c8fa24-goog