From: D Scott Phillips <scott@os.amperecomputing.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, James Morse <james.morse@arm.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Darren Hart <darren@os.amperecomputing.com>,
patches@amperecomputing.com
Subject: [PATCH v2] arm64: Fix bit-shifting UB in the MIDR_CPU_MODEL() macro
Date: Wed, 2 Nov 2022 09:01:06 -0700 [thread overview]
Message-ID: <20221102160106.1096948-1-scott@os.amperecomputing.com> (raw)
CONFIG_UBSAN_SHIFT with gcc-5 complains that the shifting of
ARM_CPU_IMP_AMPERE (0xC0) into bits [31:24] by MIDR_CPU_MODEL() is
undefined behavior. Well, sort of, it actually spells the error as:
arch/arm64/kernel/proton-pack.c: In function 'spectre_bhb_loop_affected':
arch/arm64/include/asm/cputype.h:44:2: error: initializer element is not constant
(((imp) << MIDR_IMPLEMENTOR_SHIFT) | \
^
This isn't an issue for other Implementor codes, as all the other codes
have zero in the top bit and so are representable as a signed int.
Cast the implementor code to unsigned in MIDR_CPU_MODEL to remove the
undefined behavior.
Fixes: 0e5d5ae837c8 ("arm64: Add AMPERE1 to the Spectre-BHB affected list")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
---
Changes since v1 (https://lore.kernel.org/all/20221017210119.3581-1-scott@os.amperecomputing.com/):
- cast in MIDR_CPU_MODEL() instead of changing ARM_CPU_IMP_AMPERE
arch/arm64/include/asm/cputype.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index abc418650fec..65e53ef5a396 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -41,7 +41,7 @@
(((midr) & MIDR_IMPLEMENTOR_MASK) >> MIDR_IMPLEMENTOR_SHIFT)
#define MIDR_CPU_MODEL(imp, partnum) \
- (((imp) << MIDR_IMPLEMENTOR_SHIFT) | \
+ ((_AT(u32, imp) << MIDR_IMPLEMENTOR_SHIFT) | \
(0xf << MIDR_ARCHITECTURE_SHIFT) | \
((partnum) << MIDR_PARTNUM_SHIFT))
--
2.37.3
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2022-11-02 16:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 16:01 D Scott Phillips [this message]
2022-11-09 10:26 ` [PATCH v2] arm64: Fix bit-shifting UB in the MIDR_CPU_MODEL() macro Catalin Marinas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221102160106.1096948-1-scott@os.amperecomputing.com \
--to=scott@os.amperecomputing.com \
--cc=catalin.marinas@arm.com \
--cc=darren@os.amperecomputing.com \
--cc=geert@linux-m68k.org \
--cc=james.morse@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=patches@amperecomputing.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).