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![Mathieu Desnoyers](/assets/img/avatar_default.png)
Declaring the rseq_cs field as a union between __u64 and two __u32 allows both 32-bit and 64-bit kernels to read the full __u64, and therefore validate that a 32-bit user-space cleared the upper 32 bits, thus ensuring a consistent behavior between native 32-bit kernels and 32-bit compat tasks on 64-bit kernels. Check that the rseq_cs value read is < TASK_SIZE. The asm/byteorder.h header needs to be included by rseq.h, now that it is not using linux/types_32_64.h anymore. Considering that only __32 and __u64 types are declared in linux/rseq.h, the linux/types.h header should always be included for both kernel and user-space code: including stdint.h is just for u64 and u32, which are not used in this header at all. Use copy_from_user()/clear_user() to interact with a 64-bit field, because arm32 does not implement 64-bit __get_user, and ppc32 does not 64-bit get_user. Considering that the rseq_cs pointer does not need to be loaded/stored with single-copy atomicity from the kernel anymore, we can simply use copy_from_user()/clear_user(). Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: linux-api@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Watson <davejwatson@fb.com> Cc: Paul Turner <pjt@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Chris Lameter <cl@linux.com> Cc: Ben Maurer <bmaurer@fb.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Joel Fernandes <joelaf@google.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lkml.kernel.org/r/20180709195155.7654-5-mathieu.desnoyers@efficios.com
147 lines
4.8 KiB
C
147 lines
4.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
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#ifndef _UAPI_LINUX_RSEQ_H
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#define _UAPI_LINUX_RSEQ_H
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/*
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* linux/rseq.h
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*
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* Restartable sequences system call API
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*
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* Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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*/
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#include <linux/types.h>
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#include <asm/byteorder.h>
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enum rseq_cpu_id_state {
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RSEQ_CPU_ID_UNINITIALIZED = -1,
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RSEQ_CPU_ID_REGISTRATION_FAILED = -2,
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};
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enum rseq_flags {
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RSEQ_FLAG_UNREGISTER = (1 << 0),
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};
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enum rseq_cs_flags_bit {
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RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0,
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RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1,
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RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2,
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};
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enum rseq_cs_flags {
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RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT =
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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT),
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RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL =
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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT),
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RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE =
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(1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT),
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};
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/*
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* struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always
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* contained within a single cache-line. It is usually declared as
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* link-time constant data.
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*/
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struct rseq_cs {
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/* Version of this structure. */
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__u32 version;
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/* enum rseq_cs_flags */
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__u32 flags;
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__u64 start_ip;
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/* Offset from start_ip. */
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__u64 post_commit_offset;
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__u64 abort_ip;
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} __attribute__((aligned(4 * sizeof(__u64))));
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/*
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* struct rseq is aligned on 4 * 8 bytes to ensure it is always
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* contained within a single cache-line.
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*
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* A single struct rseq per thread is allowed.
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*/
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struct rseq {
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/*
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* Restartable sequences cpu_id_start field. Updated by the
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* kernel. Read by user-space with single-copy atomicity
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* semantics. This field should only be read by the thread which
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* registered this data structure. Aligned on 32-bit. Always
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* contains a value in the range of possible CPUs, although the
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* value may not be the actual current CPU (e.g. if rseq is not
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* initialized). This CPU number value should always be compared
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* against the value of the cpu_id field before performing a rseq
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* commit or returning a value read from a data structure indexed
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* using the cpu_id_start value.
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*/
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__u32 cpu_id_start;
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/*
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* Restartable sequences cpu_id field. Updated by the kernel.
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* Read by user-space with single-copy atomicity semantics. This
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* field should only be read by the thread which registered this
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* data structure. Aligned on 32-bit. Values
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* RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
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* have a special semantic: the former means "rseq uninitialized",
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* and latter means "rseq initialization failed". This value is
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* meant to be read within rseq critical sections and compared
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* with the cpu_id_start value previously read, before performing
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* the commit instruction, or read and compared with the
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* cpu_id_start value before returning a value loaded from a data
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* structure indexed using the cpu_id_start value.
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*/
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__u32 cpu_id;
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/*
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* Restartable sequences rseq_cs field.
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*
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* Contains NULL when no critical section is active for the current
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* thread, or holds a pointer to the currently active struct rseq_cs.
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*
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* Updated by user-space, which sets the address of the currently
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* active rseq_cs at the beginning of assembly instruction sequence
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* block, and set to NULL by the kernel when it restarts an assembly
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* instruction sequence block, as well as when the kernel detects that
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* it is preempting or delivering a signal outside of the range
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* targeted by the rseq_cs. Also needs to be set to NULL by user-space
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* before reclaiming memory that contains the targeted struct rseq_cs.
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*
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* Read and set by the kernel. Set by user-space with single-copy
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* atomicity semantics. This field should only be updated by the
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* thread which registered this data structure. Aligned on 64-bit.
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*/
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union {
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__u64 ptr64;
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#ifdef __LP64__
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__u64 ptr;
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#else
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struct {
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#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)
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__u32 padding; /* Initialized to zero. */
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__u32 ptr32;
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#else /* LITTLE */
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__u32 ptr32;
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__u32 padding; /* Initialized to zero. */
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#endif /* ENDIAN */
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} ptr;
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#endif
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} rseq_cs;
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/*
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* Restartable sequences flags field.
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*
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* This field should only be updated by the thread which
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* registered this data structure. Read by the kernel.
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* Mainly used for single-stepping through rseq critical sections
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* with debuggers.
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*
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* - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
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* Inhibit instruction sequence block restart on preemption
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* for this thread.
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* - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
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* Inhibit instruction sequence block restart on signal
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* delivery for this thread.
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* - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
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* Inhibit instruction sequence block restart on migration for
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* this thread.
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*/
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__u32 flags;
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} __attribute__((aligned(4 * sizeof(__u64))));
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#endif /* _UAPI_LINUX_RSEQ_H */
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