linux-kernel - [PATCH 11/15] arm64: fix mrs_s/msr

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Date:   Fri,  3 Nov 2017 10:11:57 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 11/15] arm64: fix mrs_s/msr_s macros for clang LTO

Clang's integrated assembler does not allow assembly macros defined
in one inline asm block using the .macro directive to be used across
separate asm blocks. LLVM developers consider this a feature and not a
bug, recommending code refactoring:

  https://bugs.llvm.org/show_bug.cgi?id=19749

As binutils doesn't allow macros to be redefined, this change adds C
preprocessor macros that define the assembly macros globally for binutils
and locally for clang's integrated assembler.

Suggested-by: Greg Hackmann <ghackmann@...gle.com>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 arch/arm64/include/asm/kvm_hyp.h |  2 ++
 arch/arm64/include/asm/sysreg.h  | 71 ++++++++++++++++++++++++++++++----------
 2 files changed, 56 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 4572a9b560fa..6840704ea894 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -29,6 +29,7 @@
 	({								\
 		u64 reg;						\
 		asm volatile(ALTERNATIVE("mrs %0, " __stringify(r##nvh),\
+					 DEFINE_MRS_S			\
 					 "mrs_s %0, " __stringify(r##vh),\
 					 ARM64_HAS_VIRT_HOST_EXTN)	\
 			     : "=r" (reg));				\
@@ -39,6 +40,7 @@
 	do {								\
 		u64 __val = (u64)(v);					\
 		asm volatile(ALTERNATIVE("msr " __stringify(r##nvh) ", %x0",\
+					 DEFINE_MSR_S			\
 					 "msr_s " __stringify(r##vh) ", %x0",\
 					 ARM64_HAS_VIRT_HOST_EXTN)	\
 					 : : "rZ" (__val));		\
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index f707fed5886f..1588ac3f3690 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -463,21 +463,58 @@
 
 #include <linux/types.h>
 
-asm(
-"	.irp	num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n"
-"	.equ	.L__reg_num_x\\num, \\num\n"
-"	.endr\n"
+#define ___MRS_MSR_S_REGNUM					\
+"	.irp	num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n" \
+"	.equ	.L__reg_num_x\\num, \\num\n"			\
+"	.endr\n"						\
 "	.equ	.L__reg_num_xzr, 31\n"
-"\n"
-"	.macro	mrs_s, rt, sreg\n"
-	__emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt))
+
+#define ___MRS_S						\
+"	.macro	mrs_s, rt, sreg\n"				\
+	__emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt))	\
 "	.endm\n"
-"\n"
-"	.macro	msr_s, sreg, rt\n"
-	__emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt))
+
+#define ___MSR_S						\
+"	.macro	msr_s, sreg, rt\n"				\
+	__emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt))	\
 "	.endm\n"
+
+/*
+ * llvm-as doesn't allow macros defined in an asm block to be used in other
+ * asm blocks, which means we cannot define them globally.
+ */
+#if !defined(CONFIG_CLANG_LTO)
+asm(
+	___MRS_MSR_S_REGNUM
+	___MRS_S
+	___MSR_S
 );
 
+#undef  ___MRS_MSR_S_REGNUM
+#define ___MRS_MSR_S_REGNUM
+#undef  ___MRS_S
+#define ___MRS_S
+#undef  ___MSR_S
+#define ___MSR_S
+#endif
+
+#define DEFINE_MRS_S		\
+	___MRS_MSR_S_REGNUM	\
+	___MRS_S
+
+#define DEFINE_MSR_S		\
+	___MRS_MSR_S_REGNUM	\
+	___MSR_S
+
+
+#define __mrs_s(r, v)						\
+	DEFINE_MRS_S						\
+"	mrs_s %0, " __stringify(r) : "=r" (v)
+
+#define __msr_s(r, v)						\
+	DEFINE_MSR_S						\
+"	msr_s " __stringify(r) ", %0" : : "r" (v)
+
 /*
  * Unlike read_cpuid, calls to read_sysreg are never expected to be
  * optimized away or replaced with synthetic values.
@@ -502,15 +539,15 @@ asm(
  * For registers without architectural names, or simply unsupported by
  * GAS.
  */
-#define read_sysreg_s(r) ({						\
-	u64 __val;							\
-	asm volatile("mrs_s %0, " __stringify(r) : "=r" (__val));	\
-	__val;								\
+#define read_sysreg_s(r) ({					\
+	u64 __val;						\
+	asm volatile(__mrs_s(r, __val));			\
+	__val;							\
 })
 
-#define write_sysreg_s(v, r) do {					\
-	u64 __val = (u64)(v);						\
-	asm volatile("msr_s " __stringify(r) ", %x0" : : "rZ" (__val));	\
+#define write_sysreg_s(v, r) do {				\
+	u64 __val = (u64)(v);					\
+	asm volatile(__msr_s(r, __val));			\
 } while (0)
 
 static inline void config_sctlr_el1(u32 clear, u32 set)
-- 
2.15.0.403.gc27cc4dac6-goog