From: Nick Desaulniers <ndesaulniers@google.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>
Cc: Ilie Halip <ilie.halip@gmail.com>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
"kernelci . org bot" <bot@kernelci.org>,
Andy Shevchenko <andriy.shevchenko@intel.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Marco Elver <elver@google.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Daniel Axtens <dja@axtens.net>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v2] x86: bitops: fix build regression
Date: Wed, 6 May 2020 10:05:53 -0700 [thread overview]
Message-ID: <20200506170554.54635-1-ndesaulniers@google.com> (raw)
In-Reply-To: <CAHFW8PQ1jusUS9xNUmiwwTU3x=GCqL3AJwwirhJOAgZUjx9wVA@mail.gmail.com>
From: Ilie Halip <ilie.halip@gmail.com>
It turns out that if your config tickles __builtin_constant_p via
differences in choices to inline or not, this now produces invalid
assembly:
$ cat foo.c
long a(long b, long c) {
asm("orb\t%1, %0" : "+q"(c): "r"(b));
return c;
}
$ gcc foo.c
foo.c: Assembler messages:
foo.c:2: Error: `%rax' not allowed with `orb'
The "q" constraint only has meanting on -m32 otherwise is treated as
"r".
This is easily reproducible via Clang+CONFIG_STAGING=y+CONFIG_VT6656=m.
Without the cast to u8, gcc and clang will not select low-8-bit
registers required for the `b` suffix on `orb` and `andb`, which results
in an assembler error. Without the mask, sparse will warn about the
upper bytes of the value being truncated.
[Nick: reworded]
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/961
Link: https://lore.kernel.org/lkml/20200504193524.GA221287@google.com/
Fixes: 1651e700664b4 ("x86: Fix bitops.h warning with a moved cast")
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Reported-by: kernelci.org bot <bot@kernelci.org>
Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Suggested-by: Ilie Halip <ilie.halip@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Changes V1 -> V2:
* change authorship/signed-off-by to Ilie
* add Nathan's Tested by/reviewed by
* update commit message slightly with info sent to HPA.
arch/x86/include/asm/bitops.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index b392571c1f1d..139122e5b25b 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long *addr)
if (__builtin_constant_p(nr)) {
asm volatile(LOCK_PREFIX "orb %1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) & 0xff)
+ : "iq" ((u8)(CONST_MASK(nr) & 0xff))
: "memory");
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(bts) " %1,%0"
@@ -74,7 +74,7 @@ arch_clear_bit(long nr, volatile unsigned long *addr)
if (__builtin_constant_p(nr)) {
asm volatile(LOCK_PREFIX "andb %1,%0"
: CONST_MASK_ADDR(nr, addr)
- : "iq" (CONST_MASK(nr) ^ 0xff));
+ : "iq" ((u8)(CONST_MASK(nr) ^ 0xff)));
} else {
asm volatile(LOCK_PREFIX __ASM_SIZE(btr) " %1,%0"
: : RLONG_ADDR(addr), "Ir" (nr) : "memory");
--
2.26.2.526.g744177e7f7-goog
next prev parent reply other threads:[~2020-05-06 17:06 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 17:44 [PATCH] x86: bitops: fix build regression Nick Desaulniers
2020-05-05 18:07 ` hpa
2020-05-05 18:22 ` Nick Desaulniers
2020-05-07 11:34 ` Peter Zijlstra
2020-05-07 14:00 ` Brian Gerst
2020-05-07 19:19 ` Nick Desaulniers
2020-05-07 22:29 ` Nick Desaulniers
2020-05-08 1:57 ` Brian Gerst
2020-05-08 17:21 ` Nick Desaulniers
2020-05-08 17:31 ` H. Peter Anvin
2020-05-08 18:05 ` [PATCH v3] " Nick Desaulniers
2020-05-08 18:08 ` Nick Desaulniers
2020-05-08 18:22 ` Brian Gerst
2020-05-08 18:28 ` [PATCH v4] " Nick Desaulniers
2020-05-08 18:32 ` [PATCH v5] " Nick Desaulniers
2020-05-08 20:28 ` Nathan Chancellor
2020-05-08 23:47 ` Jesse Brandeburg
2020-05-09 4:44 ` Sedat Dilek
2020-05-09 12:20 ` Andy Shevchenko
2020-05-09 15:43 ` Brian Gerst
2020-05-11 17:22 ` Nick Desaulniers
2020-05-10 13:54 ` David Laight
2020-05-11 18:52 ` Brian Gerst
2020-05-14 23:47 ` Nick Desaulniers
2020-05-10 11:59 ` [PATCH] " David Laight
2020-05-10 12:33 ` hpa
2020-05-07 19:29 ` hpa
2020-05-06 4:30 ` Nathan Chancellor
2020-05-06 9:22 ` Sedat Dilek
2020-05-06 15:41 ` Nathan Chancellor
2020-05-06 16:37 ` Nick Desaulniers
2020-05-06 16:55 ` Ilie Halip
2020-05-06 17:05 ` Nick Desaulniers [this message]
2020-05-07 6:18 ` Brian Gerst
2020-05-07 7:02 ` hpa
2020-05-07 13:32 ` Brian Gerst
2020-05-07 15:09 ` David Laight
2020-05-07 19:31 ` hpa
2020-05-07 19:29 ` hpa
2020-05-07 7:44 ` David Laight
2020-05-07 7:59 ` hpa
2020-05-07 8:35 ` David Laight
2020-05-07 8:38 ` hpa
2020-05-07 9:17 ` Andy Shevchenko
2020-05-07 19:22 ` Nick Desaulniers
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