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authorJim Wilson <jimw@sifive.com>2018-10-16 14:42:59 -0700
committerPalmer Dabbelt <palmer@sifive.com>2018-10-22 17:38:08 -0700
commitb90edb33010bcfb9a0d74681be2cdd52300f1e69 (patch)
treeeaabf46fb352ed526a918ee7fb3ab17be4a4cc61 /arch/riscv/include
parentb8c8a9590e4fde82f8c3ee06a521763e6f21e9c8 (diff)
downloadlinux-b90edb33010bcfb9a0d74681be2cdd52300f1e69.tar.bz2
RISC-V: Add futex support.
Here is an attempt to add the missing futex support. I started with the MIPS version of futex.h and modified it until I got it working. I tested it on a HiFive Unleashed running Fedora Core 29 using the fc29 4.15 version of the kernel. This was tested against the glibc testsuite, where it fixes 14 nptl related testsuite failures. That unfortunately only tests the cmpxchg support, so I also used the testcase at the end of https://lwn.net/Articles/148830/ which tests the atomic_op functionality, except that it doesn't verify that the operations are atomic, which they obviously are. This testcase runs successfully with the patch and fails without it. I'm not a kernel expert, so there could be details I got wrong here. I wasn't sure about the memory model support, so I used aqrl which seemed safest, and didn't add fences which seemed unnecessary. I'm not sure about the copyright statements, I left in Ralf Baechle's line because I started with his code. Checkpatch reports some style problems, but it is the same style as the MIPS futex.h, and the uses of ENOSYS appear correct even though it complains about them. I don't know if any of that matters. This patch was tested on qemu with the glibc nptl/tst-cond-except testcase, and the wake_op testcase from above. Signed-off-by: Jim Wilson <jimw@sifive.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Diffstat (limited to 'arch/riscv/include')
-rw-r--r--arch/riscv/include/asm/Kbuild1
-rw-r--r--arch/riscv/include/asm/futex.h128
2 files changed, 128 insertions, 1 deletions
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index efdbe311e936..6a646d9ea780 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -13,7 +13,6 @@ generic-y += errno.h
generic-y += exec.h
generic-y += fb.h
generic-y += fcntl.h
-generic-y += futex.h
generic-y += hardirq.h
generic-y += hash.h
generic-y += hw_irq.h
diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h
new file mode 100644
index 000000000000..3b19eba1bc8e
--- /dev/null
+++ b/arch/riscv/include/asm/futex.h
@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2006 Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (c) 2018 Jim Wilson (jimw@sifive.com)
+ */
+
+#ifndef _ASM_FUTEX_H
+#define _ASM_FUTEX_H
+
+#ifndef CONFIG_RISCV_ISA_A
+/*
+ * Use the generic interrupt disabling versions if the A extension
+ * is not supported.
+ */
+#ifdef CONFIG_SMP
+#error "Can't support generic futex calls without A extension on SMP"
+#endif
+#include <asm-generic/futex.h>
+
+#else /* CONFIG_RISCV_ISA_A */
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <linux/errno.h>
+#include <asm/asm.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+{ \
+ uintptr_t tmp; \
+ __enable_user_access(); \
+ __asm__ __volatile__ ( \
+ "1: " insn " \n" \
+ "2: \n" \
+ " .section .fixup,\"ax\" \n" \
+ " .balign 4 \n" \
+ "3: li %[r],%[e] \n" \
+ " jump 2b,%[t] \n" \
+ " .previous \n" \
+ " .section __ex_table,\"a\" \n" \
+ " .balign " RISCV_SZPTR " \n" \
+ " " RISCV_PTR " 1b, 3b \n" \
+ " .previous \n" \
+ : [r] "+r" (ret), [ov] "=&r" (oldval), \
+ [u] "+m" (*uaddr), [t] "=&r" (tmp) \
+ : [op] "Jr" (oparg), [e] "i" (-EFAULT) \
+ : "memory"); \
+ __disable_user_access(); \
+}
+
+static inline int
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
+{
+ int oldval = 0, ret = 0;
+
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ __futex_atomic_op("amoswap.w.aqrl %[ov],%z[op],%[u]",
+ ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ADD:
+ __futex_atomic_op("amoadd.w.aqrl %[ov],%z[op],%[u]",
+ ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_OR:
+ __futex_atomic_op("amoor.w.aqrl %[ov],%z[op],%[u]",
+ ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ANDN:
+ __futex_atomic_op("amoand.w.aqrl %[ov],%z[op],%[u]",
+ ret, oldval, uaddr, ~oparg);
+ break;
+ case FUTEX_OP_XOR:
+ __futex_atomic_op("amoxor.w.aqrl %[ov],%z[op],%[u]",
+ ret, oldval, uaddr, oparg);
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ pagefault_enable();
+
+ if (!ret)
+ *oval = oldval;
+
+ return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ int ret = 0;
+ u32 val;
+ uintptr_t tmp;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ __enable_user_access();
+ __asm__ __volatile__ (
+ "1: lr.w.aqrl %[v],%[u] \n"
+ " bne %[v],%z[ov],3f \n"
+ "2: sc.w.aqrl %[t],%z[nv],%[u] \n"
+ " bnez %[t],1b \n"
+ "3: \n"
+ " .section .fixup,\"ax\" \n"
+ " .balign 4 \n"
+ "4: li %[r],%[e] \n"
+ " jump 3b,%[t] \n"
+ " .previous \n"
+ " .section __ex_table,\"a\" \n"
+ " .balign " RISCV_SZPTR " \n"
+ " " RISCV_PTR " 1b, 4b \n"
+ " " RISCV_PTR " 2b, 4b \n"
+ " .previous \n"
+ : [r] "+r" (ret), [v] "=&r" (val), [u] "+m" (*uaddr), [t] "=&r" (tmp)
+ : [ov] "Jr" (oldval), [nv] "Jr" (newval), [e] "i" (-EFAULT)
+ : "memory");
+ __disable_user_access();
+
+ *uval = val;
+ return ret;
+}
+
+#endif /* CONFIG_RISCV_ISA_A */
+#endif /* _ASM_FUTEX_H */