linux-kernel - [PATCH] arm64: tlb: fix ARM64_TLB_RANGE with LLVM's integrated assembler

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Date:   Wed,  5 Aug 2020 11:19:20 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Zhenyu Ye <yezhenyu2@...wei.com>
Cc:     Mark Rutland <mark.rutland@....com>, Marc Zyngier <maz@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH] arm64: tlb: fix ARM64_TLB_RANGE with LLVM's integrated assembler

Commit 7c78f67e9bd9 ("arm64: enable tlbi range instructions") breaks
LLVM's integrated assembler, because -Wa,-march is only passed to
external assemblers and therefore, the new instructions are not enabled
when IAS is used.

As binutils doesn't support .arch_extension tlb-rmi, this change adds
.arch armv8.4-a to __TLBI_0 and __TLBI_1 to fix the issue with both LLVM
IAS and binutils.

Fixes: 7c78f67e9bd9 ("arm64: enable tlbi range instructions")
Link: https://github.com/ClangBuiltLinux/linux/issues/1106
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 arch/arm64/include/asm/tlbflush.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index d493174415db..66c2aab5e9cb 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -16,6 +16,16 @@
 #include <asm/cputype.h>
 #include <asm/mmu.h>
 
+/*
+ * Enable ARMv8.4-TLBI instructions with ARM64_TLB_RANGE. Note that binutils
+ * doesn't support .arch_extension tlb-rmi, so use .arch armv8.4-a instead.
+ */
+#ifdef CONFIG_ARM64_TLB_RANGE
+#define __TLBI_PREAMBLE	".arch armv8.4-a\n"
+#else
+#define __TLBI_PREAMBLE
+#endif
+
 /*
  * Raw TLBI operations.
  *
@@ -28,14 +38,16 @@
  * not. The macros handles invoking the asm with or without the
  * register argument as appropriate.
  */
-#define __TLBI_0(op, arg) asm ("tlbi " #op "\n"				       \
+#define __TLBI_0(op, arg) asm (__TLBI_PREAMBLE				       \
+			       "tlbi " #op "\n"				       \
 		   ALTERNATIVE("nop\n			nop",		       \
 			       "dsb ish\n		tlbi " #op,	       \
 			       ARM64_WORKAROUND_REPEAT_TLBI,		       \
 			       CONFIG_ARM64_WORKAROUND_REPEAT_TLBI)	       \
 			    : : )
 
-#define __TLBI_1(op, arg) asm ("tlbi " #op ", %0\n"			       \
+#define __TLBI_1(op, arg) asm (__TLBI_PREAMBLE				       \
+			       "tlbi " #op ", %0\n"			       \
 		   ALTERNATIVE("nop\n			nop",		       \
 			       "dsb ish\n		tlbi " #op ", %0",     \
 			       ARM64_WORKAROUND_REPEAT_TLBI,		       \

base-commit: 4834ce9d8e074bb7ae197632e0708219b9f389b5
-- 
2.28.0.163.g6104cc2f0b6-goog