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Date: Fri, 24 Apr 2020 08:23:51 -0400 From: Sasha Levin <sashal@...nel.org> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org Cc: Fangrui Song <maskray@...gle.com>, Ilie Halip <ilie.halip@...il.com>, Mark Rutland <mark.rutland@....com>, Catalin Marinas <catalin.marinas@....com>, Sasha Levin <sashal@...nel.org>, linux-arm-kernel@...ts.infradead.org, clang-built-linux@...glegroups.com Subject: [PATCH AUTOSEL 4.19 14/18] arm64: Delete the space separator in __emit_inst From: Fangrui Song <maskray@...gle.com> [ Upstream commit c9a4ef66450145a356a626c833d3d7b1668b3ded ] In assembly, many instances of __emit_inst(x) expand to a directive. In a few places __emit_inst(x) is used as an assembler macro argument. For example, in arch/arm64/kvm/hyp/entry.S ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN) expands to the following by the C preprocessor: alternative_insn nop, .inst (0xd500401f | ((0) << 16 | (4) << 5) | ((!!1) << 8)), 4, 1 Both comma and space are separators, with an exception that content inside a pair of parentheses/quotes is not split, so the clang integrated assembler splits the arguments to: nop, .inst, (0xd500401f | ((0) << 16 | (4) << 5) | ((!!1) << 8)), 4, 1 GNU as preprocesses the input with do_scrub_chars(). Its arm64 backend (along with many other non-x86 backends) sees: alternative_insn nop,.inst(0xd500401f|((0)<<16|(4)<<5)|((!!1)<<8)),4,1 # .inst(...) is parsed as one argument while its x86 backend sees: alternative_insn nop,.inst (0xd500401f|((0)<<16|(4)<<5)|((!!1)<<8)),4,1 # The extra space before '(' makes the whole .inst (...) parsed as two arguments The non-x86 backend's behavior is considered unintentional (https://sourceware.org/bugzilla/show_bug.cgi?id=25750). So drop the space separator inside `.inst (...)` to make the clang integrated assembler work. Suggested-by: Ilie Halip <ilie.halip@...il.com> Signed-off-by: Fangrui Song <maskray@...gle.com> Reviewed-by: Mark Rutland <mark.rutland@....com> Link: https://github.com/ClangBuiltLinux/linux/issues/939 Signed-off-by: Catalin Marinas <catalin.marinas@....com> Signed-off-by: Sasha Levin <sashal@...nel.org> --- 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 3091ae5975a3a..ed99d941c4623 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -60,7 +60,9 @@ #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 an assembler directive or an assembler macro argument. +#define __emit_inst(x) .inst(x) #else #define __emit_inst(x) ".inst " __stringify((x)) "\n\t" #endif -- 2.20.1
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