Revision b97021f85517552ea8a0d2c1680c1ee4beab6d14 authored by Benjamin Herrenschmidt on 15 November 2011, 17:11:27 UTC, committed by Benjamin Herrenschmidt on 17 November 2011, 05:26:07 UTC
The Documentation/memory-barriers.txt document requires that atomic operations that return a value act as a memory barrier both before and after the actual atomic operation. Our current implementation doesn't guarantee this. More specifically, while a load following the isync can not be issued before stwcx. has completed, that completion doesn't architecturally means that the result of stwcx. is visible to other processors (or any previous stores for that matter) (typically, the other processors L1 caches can still hold the old value). This has caused an actual crash in RCU torture testing on Power 7 This fixes it by changing those atomic ops to use new macros instead of RELEASE/ACQUIRE barriers, called ATOMIC_ENTRY and ATMOIC_EXIT barriers, which are then defined respectively to lwsync and sync. I haven't had a chance to measure the performance impact (or rather what I measured with kernel compiles is in the noise, I yet have to find a more precise benchmark) Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
1 parent a9a8f77
compat.c
/* 32-bit compatibility syscall for 64-bit systems
*
* Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/syscalls.h>
#include <linux/keyctl.h>
#include <linux/compat.h>
#include <linux/slab.h>
#include "internal.h"
/*
* Instantiate a key with the specified compatibility multipart payload and
* link the key into the destination keyring if one is given.
*
* The caller must have the appropriate instantiation permit set for this to
* work (see keyctl_assume_authority). No other permissions are required.
*
* If successful, 0 will be returned.
*/
long compat_keyctl_instantiate_key_iov(
key_serial_t id,
const struct compat_iovec __user *_payload_iov,
unsigned ioc,
key_serial_t ringid)
{
struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
long ret;
if (_payload_iov == 0 || ioc == 0)
goto no_payload;
ret = compat_rw_copy_check_uvector(WRITE, _payload_iov, ioc,
ARRAY_SIZE(iovstack),
iovstack, &iov, 1);
if (ret < 0)
return ret;
if (ret == 0)
goto no_payload_free;
ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
if (iov != iovstack)
kfree(iov);
return ret;
no_payload_free:
if (iov != iovstack)
kfree(iov);
no_payload:
return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
}
/*
* The key control system call, 32-bit compatibility version for 64-bit archs
*
* This should only be called if the 64-bit arch uses weird pointers in 32-bit
* mode or doesn't guarantee that the top 32-bits of the argument registers on
* taking a 32-bit syscall are zero. If you can, you should call sys_keyctl()
* directly.
*/
asmlinkage long compat_sys_keyctl(u32 option,
u32 arg2, u32 arg3, u32 arg4, u32 arg5)
{
switch (option) {
case KEYCTL_GET_KEYRING_ID:
return keyctl_get_keyring_ID(arg2, arg3);
case KEYCTL_JOIN_SESSION_KEYRING:
return keyctl_join_session_keyring(compat_ptr(arg2));
case KEYCTL_UPDATE:
return keyctl_update_key(arg2, compat_ptr(arg3), arg4);
case KEYCTL_REVOKE:
return keyctl_revoke_key(arg2);
case KEYCTL_DESCRIBE:
return keyctl_describe_key(arg2, compat_ptr(arg3), arg4);
case KEYCTL_CLEAR:
return keyctl_keyring_clear(arg2);
case KEYCTL_LINK:
return keyctl_keyring_link(arg2, arg3);
case KEYCTL_UNLINK:
return keyctl_keyring_unlink(arg2, arg3);
case KEYCTL_SEARCH:
return keyctl_keyring_search(arg2, compat_ptr(arg3),
compat_ptr(arg4), arg5);
case KEYCTL_READ:
return keyctl_read_key(arg2, compat_ptr(arg3), arg4);
case KEYCTL_CHOWN:
return keyctl_chown_key(arg2, arg3, arg4);
case KEYCTL_SETPERM:
return keyctl_setperm_key(arg2, arg3);
case KEYCTL_INSTANTIATE:
return keyctl_instantiate_key(arg2, compat_ptr(arg3), arg4,
arg5);
case KEYCTL_NEGATE:
return keyctl_negate_key(arg2, arg3, arg4);
case KEYCTL_SET_REQKEY_KEYRING:
return keyctl_set_reqkey_keyring(arg2);
case KEYCTL_SET_TIMEOUT:
return keyctl_set_timeout(arg2, arg3);
case KEYCTL_ASSUME_AUTHORITY:
return keyctl_assume_authority(arg2);
case KEYCTL_GET_SECURITY:
return keyctl_get_security(arg2, compat_ptr(arg3), arg4);
case KEYCTL_SESSION_TO_PARENT:
return keyctl_session_to_parent();
case KEYCTL_REJECT:
return keyctl_reject_key(arg2, arg3, arg4, arg5);
case KEYCTL_INSTANTIATE_IOV:
return compat_keyctl_instantiate_key_iov(
arg2, compat_ptr(arg3), arg4, arg5);
default:
return -EOPNOTSUPP;
}
}
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