[RFC][PATCH 09/22] x86,futex: Remove .fixup usage

Peter Zijlstra
2021-11-04T16:56:54Z

Use the new EX_TYPE_IMM_REG to store -EFAULT into the designated 'ret'
register, this removes the need for anonymous .fixup code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/extable_fixup_types.h | 2 ++
arch/x86/include/asm/futex.h | 28 ++++++++--------------------
2 files changed, 10 insertions(+), 20 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -32,6 +32,8 @@
#define EX_TYPE_DEFAULT_MCE_SAFE 14
#define EX_TYPE_FAULT_MCE_SAFE 15
#define EX_TYPE_POP_SEG 16
+
#define EX_TYPE_IMM_REG 17 /* reg := (long)imm */
+#define EX_TYPE_EFAULT_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(-EFAULT))

#endif
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -17,13 +17,9 @@ do { \
int oldval = 0, ret; \
asm volatile("1:\t" insn "\n" \
"2:\n" \
- "\t.section .fixup,\"ax\"\n" \
- "3:\tmov\t%3, %1\n" \
- "\tjmp\t2b\n" \
- "\t.previous\n" \
- _ASM_EXTABLE_UA(1b, 3b) \
+ _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %1) \
: "=r" (oldval), "=r" (ret), "+m" (*uaddr) \
- : "i" (-EFAULT), "0" (oparg), "1" (0)); \
+ : "0" (oparg), "1" (0)); \
if (ret) \
goto label; \
*oval = oldval; \
@@ -39,15 +35,11 @@ do { \
"3:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
"\tjnz\t2b\n" \
"4:\n" \
- "\t.section .fixup,\"ax\"\n" \
- "5:\tmov\t%5, %1\n" \
- "\tjmp\t4b\n" \
- "\t.previous\n" \
- _ASM_EXTABLE_UA(1b, 5b) \
- _ASM_EXTABLE_UA(3b, 5b) \
+ _ASM_EXTABLE_TYPE_REG(1b, 4b, EX_TYPE_EFAULT_REG, %1) \
+ _ASM_EXTABLE_TYPE_REG(3b, 4b, EX_TYPE_EFAULT_REG, %1) \
: "=&a" (oldval), "=&r" (ret), \
"+m" (*uaddr), "=&r" (tem) \
- : "r" (oparg), "i" (-EFAULT), "1" (0)); \
+ : "r" (oparg), "1" (0)); \
if (ret) \
goto label; \
*oval = oldval; \
@@ -95,15 +87,11 @@ static inline int futex_atomic_cmpxchg_i
if (!user_access_begin(uaddr, sizeof(u32)))
return -EFAULT;
asm volatile("\n"
- "1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
+ "1:\t" LOCK_PREFIX "cmpxchgl %3, %2\n"
"2:\n"
- "\t.section .fixup, \"ax\"\n"
- "3:\tmov %3, %0\n"
- "\tjmp 2b\n"
- "\t.previous\n"
- _ASM_EXTABLE_UA(1b, 3b)
+ _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %0) \
: "+r" (ret), "=a" (oldval), "+m" (*uaddr)
- : "i" (-EFAULT), "r" (newval), "1" (oldval)
+ : "r" (newval), "1" (oldval)
: "memory"
);
user_access_end();