[PATCH 5.4 114/434] MIPS: futex: Emit Loongson3 sync workarounds within asm

Greg Kroah-Hartman
2019-12-29T17:45:55Z

From: Paul Burton <paul.burton@mips.com>

[ Upstream commit 3c1d3f0979721a39dd2980c97466127ce65aa130 ]

Generate the sync instructions required to workaround Loongson3 LL/SC
errata within inline asm blocks, which feels a little safer than doing
it from C where strictly speaking the compiler would be well within its
rights to insert a memory access between the separate asm statements we
previously had, containing sync & ll instructions respectively.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/mips/include/asm/barrier.h | 13 +++++++------
arch/mips/include/asm/futex.h | 15 +++++++--------
2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h
index 9228f7386220..fb842965d541 100644
--- a/arch/mips/include/asm/barrier.h
+++ b/arch/mips/include/asm/barrier.h
@@ -218,13 +218,14 @@
* ordering will be done by smp_llsc_mb() and friends.
*/
#if defined(CONFIG_WEAK_REORDERING_BEYOND_LLSC) && defined(CONFIG_SMP)
-#define __WEAK_LLSC_MB " sync \n"
-#define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory")
-#define __LLSC_CLOBBER
+# define __WEAK_LLSC_MB sync
+# define smp_llsc_mb() \
+ __asm__ __volatile__(__stringify(__WEAK_LLSC_MB) : : :"memory")
+# define __LLSC_CLOBBER
#else
-#define __WEAK_LLSC_MB " \n"
-#define smp_llsc_mb() do { } while (0)
-#define __LLSC_CLOBBER "memory"
+# define __WEAK_LLSC_MB
+# define smp_llsc_mb() do { } while (0)
+# define __LLSC_CLOBBER "memory"
#endif

#ifdef CONFIG_CPU_CAVIUM_OCTEON
diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h
index b83b0397462d..54cf20530931 100644
--- a/arch/mips/include/asm/futex.h
+++ b/arch/mips/include/asm/futex.h
@@ -16,6 +16,7 @@
#include <asm/barrier.h>
#include <asm/compiler.h>
#include <asm/errno.h>
+#include <asm/sync.h>
#include <asm/war.h>

#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
@@ -32,7 +33,7 @@
" .set arch=r4000 \n" \
"2: sc $1, %2 \n" \
" beqzl $1, 1b \n" \
- __WEAK_LLSC_MB \
+ __stringify(__WEAK_LLSC_MB) \
"3: \n" \
" .insn \n" \
" .set pop \n" \
@@ -50,19 +51,19 @@
"i" (-EFAULT) \
: "memory"); \
} else if (cpu_has_llsc) { \
- loongson_llsc_mb(); \
__asm__ __volatile__( \
" .set push \n" \
" .set noat \n" \
" .set push \n" \
" .set "MIPS_ISA_ARCH_LEVEL" \n" \
+ " " __SYNC(full, loongson3_war) " \n" \
"1: "user_ll("%1", "%4")" # __futex_atomic_op\n" \
" .set pop \n" \
" " insn " \n" \
" .set "MIPS_ISA_ARCH_LEVEL" \n" \
"2: "user_sc("$1", "%2")" \n" \
" beqz $1, 1b \n" \
- __WEAK_LLSC_MB \
+ __stringify(__WEAK_LLSC_MB) \
"3: \n" \
" .insn \n" \
" .set pop \n" \
@@ -147,7 +148,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
" .set arch=r4000 \n"
"2: sc $1, %2 \n"
" beqzl $1, 1b \n"
- __WEAK_LLSC_MB
+ __stringify(__WEAK_LLSC_MB)
"3: \n"
" .insn \n"
" .set pop \n"
@@ -164,13 +165,13 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
"i" (-EFAULT)
: "memory");
} else if (cpu_has_llsc) {
- loongson_llsc_mb();
__asm__ __volatile__(
"# futex_atomic_cmpxchg_inatomic \n"
" .set push \n"
" .set noat \n"
" .set push \n"
" .set "MIPS_ISA_ARCH_LEVEL" \n"
+ " " __SYNC(full, loongson3_war) " \n"
"1: "user_ll("%1", "%3")" \n"
" bne %1, %z4, 3f \n"
" .set pop \n"
@@ -178,8 +179,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
" .set "MIPS_ISA_ARCH_LEVEL" \n"
"2: "user_sc("$1", "%2")" \n"
" beqz $1, 1b \n"
- __WEAK_LLSC_MB
- "3: \n"
+ "3: " __SYNC_ELSE(full, loongson3_war, __WEAK_LLSC_MB) "\n"
" .insn \n"
" .set pop \n"
" .section .fixup,\"ax\" \n"
@@ -194,7 +194,6 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
: GCC_OFF_SMALL_ASM() (*uaddr), "Jr" (oldval), "Jr" (newval),
"i" (-EFAULT)
: "memory");
- loongson_llsc_mb();
} else
return -ENOSYS;

--
2.20.1