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authorFangrui Song <maskray@google.com>2020-04-14 19:32:55 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2020-04-15 15:07:12 +0300
commitc9a4ef66450145a356a626c833d3d7b1668b3ded (patch)
treec76ccbfad7b560b64fd7f61947a6bd72ac6447b7 /arch
parent9cc3d0c6915aee5140f8335d41bbc3ff1b79aa4e (diff)
downloadlinux-c9a4ef66450145a356a626c833d3d7b1668b3ded.tar.xz
arm64: Delete the space separator in __emit_inst
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@gmail.com> Signed-off-by: Fangrui Song <maskray@google.com> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Link: https://github.com/ClangBuiltLinux/linux/issues/939 Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/include/asm/sysreg.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index ebc622432831..c4ac0ac25a00 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 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