From: Fangrui Song <maskray@google.com>
To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Fangrui Song <maskray@google.com>,
clang-built-linux@googlegroups.com
Subject: [PATCH] arm64: Delete the space separator in __emit_inst
Date: Sun, 12 Apr 2020 20:38:11 -0700 [thread overview]
Message-ID: <20200413033811.75074-1-maskray@google.com> (raw)
Many instances of __emit_inst(x) expand to a directive. In a few places
it is used as a macro argument, e.g.
arch/arm64/include/asm/sysreg.h
#define __emit_inst(x) .inst (x)
arch/arm64/include/asm/sysreg.h
#define SET_PSTATE_PAN(x) __emit_inst(0xd500401f | PSTATE_PAN | ((!!x) << PSTATE_Imm_shift))
arch/arm64/kvm/hyp/entry.S
ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
Clang integrated assembler parses `.inst (x)` as two arguments passing
to a macro. We delete the space separator so that `.inst(x)` will be
parsed as one argument.
Note, GNU as parsing `.inst (x)` as one argument is unintentional (for
example the x86 backend will parse the construct as two arguments).
See https://sourceware.org/bugzilla/show_bug.cgi?id=25750#c10
Link: https://github.com/ClangBuiltLinux/linux/issues/939
Cc: clang-built-linux@googlegroups.com
Signed-off-by: Fangrui Song <maskray@google.com>
---
arch/arm64/include/asm/sysreg.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index ebc622432831..af21e2ec5e3e 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -49,7 +49,9 @@
#ifndef CONFIG_BROKEN_GAS_INST
#ifdef __ASSEMBLY__
-#define __emit_inst(x) .inst (x)
+// The space separator is omitted so that __emit_inst(x) can be parsed as
+// either a directive or a macro argument.
+#define __emit_inst(x) .inst(x)
#else
#define __emit_inst(x) ".inst " __stringify((x)) "\n\t"
#endif
--
2.26.0.110.g2183baf09c-goog
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next reply other threads:[~2020-04-13 3:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 3:38 Fangrui Song [this message]
2020-04-13 18:07 ` [PATCH] arm64: Delete the space separator in __emit_inst Nick Desaulniers
2020-04-14 9:59 ` Mark Rutland
2020-04-14 15:43 ` Fangrui Song
2020-04-14 16:07 ` Mark Rutland
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