This is a note to let you know that I've just added the patch titled
arm64: Delete the space separator in __emit_inst
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-delete-the-space-separator-in-__emit_inst.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fce8aff9958d5e9552330d93f7e1c5f6311e1bac
Author: Fangrui Song <maskray@xxxxxxxxxx>
Date: Tue Apr 14 09:32:55 2020 -0700
arm64: Delete the space separator in __emit_inst
[ 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@xxxxxxxxx>
Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx>
Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx>
Link: https://github.com/ClangBuiltLinux/linux/issues/939
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index b91570ff9db14..931037500e83c 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
