[PATCH v2] arm64: use a common .arch preamble for inline assembly

Sami Tolvanen
2020-08-27T20:36:18Z

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.

This change adds a common architecture version preamble, which can be
used in inline assembly blocks that contain instructions that require
a newer architecture version, and uses it to fix __TLBI_0 and __TLBI_1
with ARM64_TLB_RANGE.

Fixes: 7c78f67e9bd9 ("arm64: enable tlbi range instructions")
Link: https://github.com/ClangBuiltLinux/linux/issues/1106
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
Changes in v2:
- Switched to a standard preamble for the architecture version.

---
arch/arm64/Makefile | 11 ++++++++---
arch/arm64/include/asm/compiler.h | 6 ++++++
arch/arm64/include/asm/tlbflush.h | 6 ++++--
3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b45f0124cc16..20ab5c9375a5 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -82,8 +82,8 @@ endif
# compiler to generate them and consequently to break the single image contract
# we pass it only to the assembler. This option is utilized only in case of non
# integrated assemblers.
-ifneq ($(CONFIG_AS_HAS_ARMV8_4), y)
-branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
+ifeq ($(CONFIG_AS_HAS_PAC), y)
+asm-arch := armv8.3-a
endif
endif

@@ -91,7 +91,12 @@ KBUILD_CFLAGS += $(branch-prot-flags-y)

ifeq ($(CONFIG_AS_HAS_ARMV8_4), y)
# make sure to pass the newest target architecture to -march.
-KBUILD_CFLAGS += -Wa,-march=armv8.4-a
+asm-arch := armv8.4-a
+endif
+
+ifdef asm-arch
+KBUILD_CFLAGS += -Wa,-march=$(asm-arch) \
+ -DARM64_ASM_ARCH='"$(asm-arch)"'
endif

ifeq ($(CONFIG_SHADOW_CALL_STACK), y)
diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
index 51a7ce87cdfe..6fb2e6bcc392 100644
--- a/arch/arm64/include/asm/compiler.h
+++ b/arch/arm64/include/asm/compiler.h
@@ -2,6 +2,12 @@
#ifndef __ASM_COMPILER_H
#define __ASM_COMPILER_H

+#ifdef ARM64_ASM_ARCH
+#define ARM64_ASM_PREAMBLE ".arch " ARM64_ASM_ARCH "\n"
+#else
+#define ARM64_ASM_PREAMBLE
+#endif
+
/*
* The EL0/EL1 pointer bits used by a pointer authentication code.
* This is dependent on TBI0/TBI1 being enabled, or bits 63:56 would also apply.
diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index d493174415db..cc3f5a33ff9c 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -28,14 +28,16 @@
* 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 (ARM64_ASM_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 (ARM64_ASM_PREAMBLE \
+ "tlbi " #op ", %0\n" \
ALTERNATIVE("nop\n nop", \
"dsb ish\n tlbi " #op ", %0", \
ARM64_WORKAROUND_REPEAT_TLBI, \

base-commit: 15bc20c6af4ceee97a1f90b43c0e386643c071b4
--
2.28.0.297.g1956fa8f8d-goog