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Subject[RFC][PATCH v2 5/8] x86: convert arch_futex_atomic_op_inuser() to user_access_begin/user_access_end()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Lift stac/clac pairs from __futex_atomic_op{1,2} into arch_futex_atomic_op_inuser(),
fold them with access_ok() in there. The switch in arch_futex_atomic_op_inuser()
is what has required the previous (objtool) commit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/include/asm/futex.h | 62 +++++++++++++++++++++++++-------------------
1 file changed, 36 insertions(+), 26 deletions(-)

diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index 6bcd1c1486d9..53c07ab63762 100644
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -12,26 +12,33 @@
#include <asm/processor.h>
#include <asm/smap.h>

-#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
- asm volatile("\t" ASM_STAC "\n" \
- "1:\t" insn "\n" \
- "2:\t" ASM_CLAC "\n" \
+#define unsafe_atomic_op1(insn, oval, uaddr, oparg, label) \
+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) \
: "=r" (oldval), "=r" (ret), "+m" (*uaddr) \
- : "i" (-EFAULT), "0" (oparg), "1" (0))
+ : "i" (-EFAULT), "0" (oparg), "1" (0)); \
+ if (ret) \
+ goto label; \
+ *oval = oldval; \
+} while(0)

-#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
- asm volatile("\t" ASM_STAC "\n" \
- "1:\tmovl %2, %0\n" \
+
+#define unsafe_atomic_op2(insn, oval, uaddr, oparg, label) \
+do { \
+ int oldval = 0, ret, tem; \
+ asm volatile("1:\tmovl %2, %0\n" \
"\tmovl\t%0, %3\n" \
"\t" insn "\n" \
"2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
"\tjnz\t1b\n" \
- "3:\t" ASM_CLAC "\n" \
+ "3:\n" \
"\t.section .fixup,\"ax\"\n" \
"4:\tmov\t%5, %1\n" \
"\tjmp\t3b\n" \
@@ -40,41 +47,44 @@
_ASM_EXTABLE_UA(2b, 4b) \
: "=&a" (oldval), "=&r" (ret), \
"+m" (*uaddr), "=&r" (tem) \
- : "r" (oparg), "i" (-EFAULT), "1" (0))
+ : "r" (oparg), "i" (-EFAULT), "1" (0)); \
+ if (ret) \
+ goto label; \
+ *oval = oldval; \
+} while(0)

-static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+static __always_inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
u32 __user *uaddr)
{
- int oldval = 0, ret, tem;
-
- if (!access_ok(uaddr, sizeof(u32)))
+ if (!user_access_begin(uaddr, sizeof(u32)))
return -EFAULT;

switch (op) {
case FUTEX_OP_SET:
- __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
+ unsafe_atomic_op1("xchgl %0, %2", oval, uaddr, oparg, Efault);
break;
case FUTEX_OP_ADD:
- __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
- uaddr, oparg);
+ unsafe_atomic_op1(LOCK_PREFIX "xaddl %0, %2", oval,
+ uaddr, oparg, Efault);
break;
case FUTEX_OP_OR:
- __futex_atomic_op2("orl %4, %3", ret, oldval, uaddr, oparg);
+ unsafe_atomic_op2("orl %4, %3", oval, uaddr, oparg, Efault);
break;
case FUTEX_OP_ANDN:
- __futex_atomic_op2("andl %4, %3", ret, oldval, uaddr, ~oparg);
+ unsafe_atomic_op2("andl %4, %3", oval, uaddr, ~oparg, Efault);
break;
case FUTEX_OP_XOR:
- __futex_atomic_op2("xorl %4, %3", ret, oldval, uaddr, oparg);
+ unsafe_atomic_op2("xorl %4, %3", oval, uaddr, oparg, Efault);
break;
default:
- ret = -ENOSYS;
+ user_access_end();
+ return -ENOSYS;
}
-
- if (!ret)
- *oval = oldval;
-
- return ret;
+ user_access_end();
+ return 0;
+Efault:
+ user_access_end();
+ return -EFAULT;
}

static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
--
2.11.0
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