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>
2018-10-16 17:42:59 -04:00
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (c) 2006 Ralf Baechle (ralf@linux-mips.org)
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* Copyright (c) 2018 Jim Wilson (jimw@sifive.com)
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*/
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#ifndef _ASM_FUTEX_H
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#define _ASM_FUTEX_H
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#include <linux/futex.h>
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#include <linux/uaccess.h>
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#include <linux/errno.h>
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#include <asm/asm.h>
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#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
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{ \
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uintptr_t tmp; \
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__enable_user_access(); \
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__asm__ __volatile__ ( \
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"1: " insn " \n" \
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"2: \n" \
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" .section .fixup,\"ax\" \n" \
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" .balign 4 \n" \
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"3: li %[r],%[e] \n" \
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" jump 2b,%[t] \n" \
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" .previous \n" \
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" .section __ex_table,\"a\" \n" \
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" .balign " RISCV_SZPTR " \n" \
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" " RISCV_PTR " 1b, 3b \n" \
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" .previous \n" \
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: [r] "+r" (ret), [ov] "=&r" (oldval), \
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[u] "+m" (*uaddr), [t] "=&r" (tmp) \
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: [op] "Jr" (oparg), [e] "i" (-EFAULT) \
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: "memory"); \
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__disable_user_access(); \
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}
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static inline int
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arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
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{
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int oldval = 0, ret = 0;
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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("amoswap.w.aqrl %[ov],%z[op],%[u]",
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ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ADD:
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__futex_atomic_op("amoadd.w.aqrl %[ov],%z[op],%[u]",
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ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_OR:
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__futex_atomic_op("amoor.w.aqrl %[ov],%z[op],%[u]",
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ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ANDN:
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__futex_atomic_op("amoand.w.aqrl %[ov],%z[op],%[u]",
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ret, oldval, uaddr, ~oparg);
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break;
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case FUTEX_OP_XOR:
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__futex_atomic_op("amoxor.w.aqrl %[ov],%z[op],%[u]",
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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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if (!ret)
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*oval = oldval;
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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 val;
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uintptr_t tmp;
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Remove 'type' argument from access_ok() function
Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.
It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access. But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.
A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model. And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.
This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.
There were a couple of notable cases:
- csky still had the old "verify_area()" name as an alias.
- the iter_iov code had magical hardcoded knowledge of the actual
values of VERIFY_{READ,WRITE} (not that they mattered, since nothing
really used it)
- microblaze used the type argument for a debug printout
but other than those oddities this should be a total no-op patch.
I tried to fix up all architectures, did fairly extensive grepping for
access_ok() uses, and the changes are trivial, but I may have missed
something. Any missed conversion should be trivially fixable, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-03 21:57:57 -05:00
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if (!access_ok(uaddr, sizeof(u32)))
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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>
2018-10-16 17:42:59 -04:00
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return -EFAULT;
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__enable_user_access();
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__asm__ __volatile__ (
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"1: lr.w.aqrl %[v],%[u] \n"
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" bne %[v],%z[ov],3f \n"
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"2: sc.w.aqrl %[t],%z[nv],%[u] \n"
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" bnez %[t],1b \n"
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"3: \n"
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" .section .fixup,\"ax\" \n"
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" .balign 4 \n"
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"4: li %[r],%[e] \n"
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" jump 3b,%[t] \n"
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" .previous \n"
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" .section __ex_table,\"a\" \n"
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" .balign " RISCV_SZPTR " \n"
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" " RISCV_PTR " 1b, 4b \n"
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" " RISCV_PTR " 2b, 4b \n"
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" .previous \n"
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: [r] "+r" (ret), [v] "=&r" (val), [u] "+m" (*uaddr), [t] "=&r" (tmp)
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: [ov] "Jr" (oldval), [nv] "Jr" (newval), [e] "i" (-EFAULT)
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: "memory");
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__disable_user_access();
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*uval = val;
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return ret;
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}
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#endif /* _ASM_FUTEX_H */
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