From 3f2bedabb62c6210df63b604dc988d2f7f56f947 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 26 Oct 2021 12:03:47 +0200 Subject: futex: Ensure futex_atomic_cmpxchg_inatomic() is present The boot-time detection of futex_atomic_cmpxchg_inatomic() has a bug on some 32-bit arm builds, and Thomas Gleixner suggested that setting CONFIG_HAVE_FUTEX_CMPXCHG would avoid the problem, as it is always present anyway. Looking into which other architectures could do the same showed that almost all architectures have it, the exceptions being: - some old 32-bit MIPS uniprocessor cores without ll/sc - one xtensa variant with no SMP - 32-bit SPARC when built for SMP Fix MIPS And Xtensa by rearranging the generic code to let it be used as a fallback. For SPARC, the SMP definition just ends up turning off futex anyway, so this can be done at Kconfig time instead. Note that sparc32 glibc requires the CASA instruction for its mutexes anyway, which is only available when running on SPARCv9 or LEON CPUs, but needs to be implemented in the sparc32 kernel for those. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Acked-by: Max Filippov Acked-by: Geert Uytterhoeven Acked-by: Rich Felker Link: https://lore.kernel.org/r/20211026100432.1730393-1-arnd@kernel.org --- arch/mips/include/asm/futex.h | 29 ++++++++++++++++++----------- arch/xtensa/include/asm/futex.h | 8 ++++++-- 2 files changed, 24 insertions(+), 13 deletions(-) (limited to 'arch') diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h index d85248404c52..9287110cb06d 100644 --- a/arch/mips/include/asm/futex.h +++ b/arch/mips/include/asm/futex.h @@ -19,7 +19,11 @@ #include #include -#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \ +#define arch_futex_atomic_op_inuser arch_futex_atomic_op_inuser +#define futex_atomic_cmpxchg_inatomic futex_atomic_cmpxchg_inatomic +#include + +#define __futex_atomic_op(op, insn, ret, oldval, uaddr, oparg) \ { \ if (cpu_has_llsc && IS_ENABLED(CONFIG_WAR_R10000_LLSC)) { \ __asm__ __volatile__( \ @@ -80,9 +84,11 @@ : "0" (0), GCC_OFF_SMALL_ASM() (*uaddr), "Jr" (oparg), \ "i" (-EFAULT) \ : "memory"); \ - } else \ - ret = -ENOSYS; \ -} + } else { \ + /* fallback for non-SMP */ \ + ret = arch_futex_atomic_op_inuser_local(op, oparg, oval,\ + uaddr); \ + } static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr) @@ -94,23 +100,23 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr) switch (op) { case FUTEX_OP_SET: - __futex_atomic_op("move $1, %z5", ret, oldval, uaddr, oparg); + __futex_atomic_op(op, "move $1, %z5", ret, oldval, uaddr, oparg); break; case FUTEX_OP_ADD: - __futex_atomic_op("addu $1, %1, %z5", + __futex_atomic_op(op, "addu $1, %1, %z5", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: - __futex_atomic_op("or $1, %1, %z5", + __futex_atomic_op(op, "or $1, %1, %z5", ret, oldval, uaddr, oparg); break; case FUTEX_OP_ANDN: - __futex_atomic_op("and $1, %1, %z5", + __futex_atomic_op(op, "and $1, %1, %z5", ret, oldval, uaddr, ~oparg); break; case FUTEX_OP_XOR: - __futex_atomic_op("xor $1, %1, %z5", + __futex_atomic_op(op, "xor $1, %1, %z5", ret, oldval, uaddr, oparg); break; default: @@ -193,8 +199,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, : GCC_OFF_SMALL_ASM() (*uaddr), "Jr" (oldval), "Jr" (newval), "i" (-EFAULT) : "memory"); - } else - return -ENOSYS; + } else { + return futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval); + } *uval = val; return ret; diff --git a/arch/xtensa/include/asm/futex.h b/arch/xtensa/include/asm/futex.h index a1a27b2ea460..fe8f31575ab1 100644 --- a/arch/xtensa/include/asm/futex.h +++ b/arch/xtensa/include/asm/futex.h @@ -16,6 +16,10 @@ #include #include +#define arch_futex_atomic_op_inuser arch_futex_atomic_op_inuser +#define futex_atomic_cmpxchg_inatomic futex_atomic_cmpxchg_inatomic +#include + #if XCHAL_HAVE_EXCLUSIVE #define __futex_atomic_op(insn, ret, old, uaddr, arg) \ __asm__ __volatile( \ @@ -105,7 +109,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, return ret; #else - return -ENOSYS; + return arch_futex_atomic_op_inuser_local(op, oparg, oval, uaddr); #endif } @@ -156,7 +160,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, return ret; #else - return -ENOSYS; + return futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval); #endif } -- cgit v1.2.3-59-g8ed1b