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