linux-kernel - [tip: objtool/urgent] objtool/x86: Fix elf_add

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Date:   Wed, 12 May 2021 19:20:13 -0000
From:   "tip-bot2 for Vasily Gorbik" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Vasily Gorbik <gor@...ux.ibm.com>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: objtool/urgent] objtool/x86: Fix elf_add_alternative() endianness

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     f66c05d6baf36069c01a02f869bebb75586f2318
Gitweb:        https://git.kernel.org/tip/f66c05d6baf36069c01a02f869bebb75586f2318
Author:        Vasily Gorbik <gor@...ux.ibm.com>
AuthorDate:    Wed, 12 May 2021 19:42:13 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 12 May 2021 21:17:01 +02:00

objtool/x86: Fix elf_add_alternative() endianness

Currently x86 kernel cross-compiled on big endian system fails at boot with:

  kernel BUG at arch/x86/kernel/alternative.c:258!

Corresponding bug condition look like the following:

  BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32);

Fix that by converting alternative feature/cpuid to target endianness.

Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: https://lore.kernel.org/r/patch-2.thread-6c9df9.git-6c9df9a8098d.your-ad-here.call-01620841104-ext-2554@work.hours
---
 tools/objtool/arch/x86/decode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index cedf3ed..24295d3 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -19,6 +19,7 @@
 #include <objtool/elf.h>
 #include <objtool/arch.h>
 #include <objtool/warn.h>
+#include <objtool/endianness.h>
 #include <arch/elf.h>
 
 static int is_x86_64(const struct elf *elf)
@@ -725,7 +726,7 @@ static int elf_add_alternative(struct elf *elf,
 		return -1;
 	}
 
-	alt->cpuid = cpuid;
+	alt->cpuid = bswap_if_needed(cpuid);
 	alt->instrlen = orig_len;
 	alt->replacementlen = repl_len;