linux-kernel - [PATCH AUTOSEL 5.15 18/41] powerpc/prom_init: Fix build failure with GCC_PLUGIN_STRUCTLEAK_BYREF

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Message-Id: <20220628022100.595243-18-sashal@kernel.org>
Date:   Mon, 27 Jun 2022 22:20:37 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>, aneesh.kumar@...ux.ibm.com,
        rafael.j.wysocki@...el.com, joel@....id.au, adobriyan@...il.com,
        Julia.Lawall@...ia.fr, jlu.hpw@...mail.com, nick.child@....com,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 5.15 18/41] powerpc/prom_init: Fix build failure with GCC_PLUGIN_STRUCTLEAK_BYREF_ALL and KASAN

From: Christophe Leroy <christophe.leroy@...roup.eu>

[ Upstream commit ca5dabcff1df6bc8c413922b5fa63cc602858803 ]

When CONFIG_KASAN is selected, we expect prom_init to use __memset()
because it is too early to use memset().

But with CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL, the compiler adds calls
to memset() to clear objects on stack, hence the following failure:

	  PROMCHK arch/powerpc/kernel/prom_init_check
	Error: External symbol 'memset' referenced from prom_init.c
	make[2]: *** [arch/powerpc/kernel/Makefile:204 : arch/powerpc/kernel/prom_init_check] Erreur 1

prom_find_machine_type() is called from prom_init() and is called only
once, so lets put compat[] in BSS instead of stack to avoid that.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/3802811f7cf94f730be44688539c01bba3a3b5c0.1654875808.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/prom_init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index f845065c860e..ff685940e272 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -2300,7 +2300,7 @@ static void __init prom_init_stdout(void)
 
 static int __init prom_find_machine_type(void)
 {
-	char compat[256];
+	static char compat[256] __prombss;
 	int len, i = 0;
 #ifdef CONFIG_PPC64
 	phandle rtas;
-- 
2.35.1