1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Access to user system call parameters and results 4 * 5 * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. 6 * 7 * This file is a stub providing documentation for what functions 8 * asm-ARCH/syscall.h files need to define. Most arch definitions 9 * will be simple inlines. 10 * 11 * All of these functions expect to be called with no locks, 12 * and only when the caller is sure that the task of interest 13 * cannot return to user mode while we are looking at it. 14 */ 15 16 #ifndef _ASM_SYSCALL_H 17 #define _ASM_SYSCALL_H 1 18 19 struct task_struct; 20 struct pt_regs; 21 22 /** 23 * syscall_get_nr - find what system call a task is executing 24 * @task: task of interest, must be blocked 25 * @regs: task_pt_regs() of @task 26 * 27 * If @task is executing a system call or is at system call 28 * tracing about to attempt one, returns the system call number. 29 * If @task is not executing a system call, i.e. it's blocked 30 * inside the kernel for a fault or signal, returns -1. 31 * 32 * Note this returns int even on 64-bit machines. Only 32 bits of 33 * system call number can be meaningful. If the actual arch value 34 * is 64 bits, this truncates to 32 bits so 0xffffffff means -1. 35 * 36 * It's only valid to call this when @task is known to be blocked. 37 */ 38 int syscall_get_nr(struct task_struct *task, struct pt_regs *regs); 39 40 /** 41 * syscall_rollback - roll back registers after an aborted system call 42 * @task: task of interest, must be in system call exit tracing 43 * @regs: task_pt_regs() of @task 44 * 45 * It's only valid to call this when @task is stopped for system 46 * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT), 47 * after tracehook_report_syscall_entry() returned nonzero to prevent 48 * the system call from taking place. 49 * 50 * This rolls back the register state in @regs so it's as if the 51 * system call instruction was a no-op. The registers containing 52 * the system call number and arguments are as they were before the 53 * system call instruction. This may not be the same as what the 54 * register state looked like at system call entry tracing. 55 */ 56 void syscall_rollback(struct task_struct *task, struct pt_regs *regs); 57 58 /** 59 * syscall_get_error - check result of traced system call 60 * @task: task of interest, must be blocked 61 * @regs: task_pt_regs() of @task 62 * 63 * Returns 0 if the system call succeeded, or -ERRORCODE if it failed. 64 * 65 * It's only valid to call this when @task is stopped for tracing on exit 66 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 67 */ 68 long syscall_get_error(struct task_struct *task, struct pt_regs *regs); 69 70 /** 71 * syscall_get_return_value - get the return value of a traced system call 72 * @task: task of interest, must be blocked 73 * @regs: task_pt_regs() of @task 74 * 75 * Returns the return value of the successful system call. 76 * This value is meaningless if syscall_get_error() returned nonzero. 77 * 78 * It's only valid to call this when @task is stopped for tracing on exit 79 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 80 */ 81 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs); 82 83 /** 84 * syscall_set_return_value - change the return value of a traced system call 85 * @task: task of interest, must be blocked 86 * @regs: task_pt_regs() of @task 87 * @error: negative error code, or zero to indicate success 88 * @val: user return value if @error is zero 89 * 90 * This changes the results of the system call that user mode will see. 91 * If @error is zero, the user sees a successful system call with a 92 * return value of @val. If @error is nonzero, it's a negated errno 93 * code; the user sees a failed system call with this errno code. 94 * 95 * It's only valid to call this when @task is stopped for tracing on exit 96 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 97 */ 98 void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs, 99 int error, long val); 100 101 /** 102 * syscall_get_arguments - extract system call parameter values 103 * @task: task of interest, must be blocked 104 * @regs: task_pt_regs() of @task 105 * @args: array filled with argument values 106 * 107 * Fetches 6 arguments to the system call. First argument is stored in 108 * @args[0], and so on. 109 * 110 * It's only valid to call this when @task is stopped for tracing on 111 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 112 */ 113 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, 114 unsigned long *args); 115 116 /** 117 * syscall_set_arguments - change system call parameter value 118 * @task: task of interest, must be in system call entry tracing 119 * @regs: task_pt_regs() of @task 120 * @args: array of argument values to store 121 * 122 * Changes 6 arguments to the system call. 123 * The first argument gets value @args[0], and so on. 124 * 125 * It's only valid to call this when @task is stopped for tracing on 126 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 127 */ 128 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs, 129 const unsigned long *args); 130 131 /** 132 * syscall_get_arch - return the AUDIT_ARCH for the current system call 133 * @task: task of interest, must be blocked 134 * 135 * Returns the AUDIT_ARCH_* based on the system call convention in use. 136 * 137 * It's only valid to call this when @task is stopped on entry to a system 138 * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP. 139 * 140 * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must 141 * provide an implementation of this. 142 */ 143 int syscall_get_arch(struct task_struct *task); 144 #endif /* _ASM_SYSCALL_H */