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Diffstat (limited to 'include/uapi/linux/rseq.h')
| -rw-r--r-- | include/uapi/linux/rseq.h | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h new file mode 100644 index 000000000..ca6fe1f9d --- /dev/null +++ b/include/uapi/linux/rseq.h @@ -0,0 +1,210 @@ +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_RSEQ_H +#define _UAPI_LINUX_RSEQ_H + +/* + * linux/rseq.h + * + * Restartable sequences system call API + * + * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> + */ + +#include <linux/types.h> +#include <asm/byteorder.h> + +enum rseq_cpu_id_state { + RSEQ_CPU_ID_UNINITIALIZED = -1, + RSEQ_CPU_ID_REGISTRATION_FAILED = -2, +}; + +enum rseq_flags { + RSEQ_FLAG_UNREGISTER = (1 << 0), + RSEQ_FLAG_SLICE_EXT_DEFAULT_ON = (1 << 1), +}; + +enum rseq_cs_flags_bit { + /* Historical and unsupported bits */ + RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0, + RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1, + RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2, + /* (3) Intentional gap to keep new bits separate */ + + /* User read only feature flags */ + RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE_BIT = 4, + RSEQ_CS_FLAG_SLICE_EXT_ENABLED_BIT = 5, +}; + +enum rseq_cs_flags { + RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT = + (1U << RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT), + RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL = + (1U << RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT), + RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE = + (1U << RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT), + + RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE = + (1U << RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE_BIT), + RSEQ_CS_FLAG_SLICE_EXT_ENABLED = + (1U << RSEQ_CS_FLAG_SLICE_EXT_ENABLED_BIT), +}; + +/* + * struct rseq_cs is aligned on 4 * 8 bytes to ensure it is always + * contained within a single cache-line. It is usually declared as + * link-time constant data. + */ +struct rseq_cs { + /* Version of this structure. */ + __u32 version; + /* enum rseq_cs_flags */ + __u32 flags; + __u64 start_ip; + /* Offset from start_ip. */ + __u64 post_commit_offset; + __u64 abort_ip; +} __attribute__((aligned(4 * sizeof(__u64)))); + +/** + * rseq_slice_ctrl - Time slice extension control structure + * @all: Compound value + * @request: Request for a time slice extension + * @granted: Granted time slice extension + * + * @request is set by user space and can be cleared by user space or kernel + * space. @granted is set and cleared by the kernel and must only be read + * by user space. + */ +struct rseq_slice_ctrl { + union { + __u32 all; + struct { + __u8 request; + __u8 granted; + __u16 __reserved; + }; + }; +}; + +/* + * The original size and alignment of the allocation for struct rseq is + * 32 bytes. + * + * The allocation size needs to be greater or equal to + * max(getauxval(AT_RSEQ_FEATURE_SIZE), 32), and the allocation needs to + * be aligned on max(getauxval(AT_RSEQ_ALIGN), 32). + * + * As an alternative, userspace is allowed to use both the original size + * and alignment of 32 bytes for backward compatibility. + * + * A single active struct rseq registration per thread is allowed. + */ +struct rseq { + /* + * Restartable sequences cpu_id_start field. Updated by the + * kernel. Read by user-space with single-copy atomicity + * semantics. This field should only be read by the thread which + * registered this data structure. Aligned on 32-bit. Always + * contains a value in the range of possible CPUs, although the + * value may not be the actual current CPU (e.g. if rseq is not + * initialized). This CPU number value should always be compared + * against the value of the cpu_id field before performing a rseq + * commit or returning a value read from a data structure indexed + * using the cpu_id_start value. + */ + __u32 cpu_id_start; + /* + * Restartable sequences cpu_id field. Updated by the kernel. + * Read by user-space with single-copy atomicity semantics. This + * field should only be read by the thread which registered this + * data structure. Aligned on 32-bit. Values + * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED + * have a special semantic: the former means "rseq uninitialized", + * and latter means "rseq initialization failed". This value is + * meant to be read within rseq critical sections and compared + * with the cpu_id_start value previously read, before performing + * the commit instruction, or read and compared with the + * cpu_id_start value before returning a value loaded from a data + * structure indexed using the cpu_id_start value. + */ + __u32 cpu_id; + /* + * Restartable sequences rseq_cs field. + * + * Contains NULL when no critical section is active for the current + * thread, or holds a pointer to the currently active struct rseq_cs. + * + * Updated by user-space, which sets the address of the currently + * active rseq_cs at the beginning of assembly instruction sequence + * block, and set to NULL by the kernel when it restarts an assembly + * instruction sequence block, as well as when the kernel detects that + * it is preempting or delivering a signal outside of the range + * targeted by the rseq_cs. Also needs to be set to NULL by user-space + * before reclaiming memory that contains the targeted struct rseq_cs. + * + * Read and set by the kernel. Set by user-space with single-copy + * atomicity semantics. This field should only be updated by the + * thread which registered this data structure. Aligned on 64-bit. + * + * 32-bit architectures should update the low order bits of the + * rseq_cs field, leaving the high order bits initialized to 0. + */ + __u64 rseq_cs; + + /* + * Restartable sequences flags field. + * + * This field was initially intended to allow event masking for + * single-stepping through rseq critical sections with debuggers. + * The kernel does not support this anymore and the relevant bits + * are checked for being always false: + * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT + * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL + * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE + * + * It is now used for feature status advertisement by the kernel. + * See: enum rseq_cs_flags_bit for further information. + */ + __u32 flags; + + /* + * Restartable sequences node_id field. Updated by the kernel. Read by + * user-space with single-copy atomicity semantics. This field should + * only be read by the thread which registered this data structure. + * Aligned on 32-bit. Contains the current NUMA node ID. + */ + __u32 node_id; + + /* + * Restartable sequences mm_cid field. Updated by the kernel. Read by + * user-space with single-copy atomicity semantics. This field should + * only be read by the thread which registered this data structure. + * Aligned on 32-bit. Contains the current thread's concurrency ID + * (allocated uniquely within a memory map). + */ + __u32 mm_cid; + + /* + * Time slice extension control structure. CPU local updates from + * kernel and user space. + */ + struct rseq_slice_ctrl slice_ctrl; + + /* + * Before rseq became extensible, its original size was 32 bytes even + * though the active rseq area was only 20 bytes. + * Exposing a 32 bytes feature size would make life needlessly painful + * for userspace. Therefore, add a reserved byte after byte 32 + * to bump the rseq feature size from 32 to 33. + * The next field to be added to the rseq area will be larger + * than one byte, and will replace this reserved byte. + */ + __u8 __reserved; + + /* + * Flexible array member at end of structure, after last feature field. + */ + char end[]; +} __attribute__((aligned(32))); + +#endif /* _UAPI_LINUX_RSEQ_H */ |