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38a0d0cdb4
We see warnings such as:
kernel/futex.c: In function 'do_futex':
kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized]
return oldval == cmparg;
^
kernel/futex.c:1651:6: note: 'oldval' was declared here
int oldval, ret;
^
This is because arch_futex_atomic_op_inuser() only sets *oval if ret
is 0 and GCC doesn't see that it will only use it when ret is 0.
Anyway, the non-zero ret path is an error path that won't suffer from
setting *oval, and as *oval is a local var in futex_atomic_op_inuser()
it will have no impact.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: reword change log slightly]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/86b72f0c134367b214910b27b9a6dd3321af93bb.1565774657.git.christophe.leroy@c-s.fr
106 lines
2.4 KiB
C
106 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_FUTEX_H
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#define _ASM_POWERPC_FUTEX_H
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#ifdef __KERNEL__
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#include <linux/futex.h>
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#include <linux/uaccess.h>
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#include <asm/errno.h>
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#include <asm/synch.h>
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#include <asm/asm-405.h>
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#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
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__asm__ __volatile ( \
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PPC_ATOMIC_ENTRY_BARRIER \
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"1: lwarx %0,0,%2\n" \
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insn \
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PPC405_ERR77(0, %2) \
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"2: stwcx. %1,0,%2\n" \
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"bne- 1b\n" \
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PPC_ATOMIC_EXIT_BARRIER \
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"li %1,0\n" \
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"3: .section .fixup,\"ax\"\n" \
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"4: li %1,%3\n" \
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"b 3b\n" \
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".previous\n" \
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EX_TABLE(1b, 4b) \
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EX_TABLE(2b, 4b) \
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: "=&r" (oldval), "=&r" (ret) \
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: "b" (uaddr), "i" (-EFAULT), "r" (oparg) \
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: "cr0", "memory")
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static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
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u32 __user *uaddr)
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{
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int oldval = 0, ret;
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allow_write_to_user(uaddr, sizeof(*uaddr));
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pagefault_disable();
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switch (op) {
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case FUTEX_OP_SET:
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__futex_atomic_op("mr %1,%4\n", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ADD:
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__futex_atomic_op("add %1,%0,%4\n", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_OR:
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__futex_atomic_op("or %1,%0,%4\n", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ANDN:
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__futex_atomic_op("andc %1,%0,%4\n", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_XOR:
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__futex_atomic_op("xor %1,%0,%4\n", ret, oldval, uaddr, oparg);
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break;
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default:
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ret = -ENOSYS;
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}
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pagefault_enable();
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*oval = oldval;
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prevent_write_to_user(uaddr, sizeof(*uaddr));
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return ret;
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}
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static inline int
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futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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u32 oldval, u32 newval)
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{
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int ret = 0;
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u32 prev;
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if (!access_ok(uaddr, sizeof(u32)))
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return -EFAULT;
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allow_write_to_user(uaddr, sizeof(*uaddr));
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__asm__ __volatile__ (
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PPC_ATOMIC_ENTRY_BARRIER
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"1: lwarx %1,0,%3 # futex_atomic_cmpxchg_inatomic\n\
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cmpw 0,%1,%4\n\
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bne- 3f\n"
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PPC405_ERR77(0,%3)
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"2: stwcx. %5,0,%3\n\
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bne- 1b\n"
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PPC_ATOMIC_EXIT_BARRIER
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"3: .section .fixup,\"ax\"\n\
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4: li %0,%6\n\
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b 3b\n\
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.previous\n"
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EX_TABLE(1b, 4b)
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EX_TABLE(2b, 4b)
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: "+r" (ret), "=&r" (prev), "+m" (*uaddr)
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: "r" (uaddr), "r" (oldval), "r" (newval), "i" (-EFAULT)
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: "cc", "memory");
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*uval = prev;
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prevent_write_to_user(uaddr, sizeof(*uaddr));
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return ret;
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}
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_FUTEX_H */
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