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rseq.h
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/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ #ifndef _LINUX_RSEQ_H #define _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), }; enum rseq_cs_flags_bit { 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, }; 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), }; /* * 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)))); /* * struct rseq is aligned on 4 * 8 bytes to ensure it is always * contained within a single cache-line. * * A single struct rseq 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. */ union { __u64 ptr64; #ifdef __LP64__ __u64 ptr; #else struct { #if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN) __u32 padding; /* Initialized to zero. */ __u32 ptr32; #else /* LITTLE */ __u32 ptr32; __u32 padding; /* Initialized to zero. */ #endif /* ENDIAN */ } ptr; #endif } rseq_cs; /* * Restartable sequences flags field. * * This field should only be updated by the thread which * registered this data structure. Read by the kernel. * Mainly used for single-stepping through rseq critical sections * with debuggers. * * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT * Inhibit instruction sequence block restart on preemption * for this thread. * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL * Inhibit instruction sequence block restart on signal * delivery for this thread. * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE * Inhibit instruction sequence block restart on migration for * this thread. */ __u32 flags; } __attribute__((aligned(4 * sizeof(__u64)))); #endif /* _LINUX_RSEQ_H */