1/* 2 * Access to user system call parameters and results 3 * 4 * Copyright (C) 2008-2009 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 * Note this returns int even on 64-bit machines. Only 32 bits of 36 * system call number can be meaningful. If the actual arch value 37 * is 64 bits, this truncates to 32 bits so 0xffffffff means -1. 38 * 39 * It's only valid to call this when @task is known to be blocked. 40 */ 41int syscall_get_nr(struct task_struct *task, struct pt_regs *regs); 42 43/** 44 * syscall_rollback - roll back registers after an aborted system call 45 * @task: task of interest, must be in system call exit tracing 46 * @regs: task_pt_regs() of @task 47 * 48 * It's only valid to call this when @task is stopped for system 49 * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT), 50 * after tracehook_report_syscall_entry() returned nonzero to prevent 51 * the system call from taking place. 52 * 53 * This rolls back the register state in @regs so it's as if the 54 * system call instruction was a no-op. The registers containing 55 * the system call number and arguments are as they were before the 56 * system call instruction. This may not be the same as what the 57 * register state looked like at system call entry tracing. 58 */ 59void syscall_rollback(struct task_struct *task, struct pt_regs *regs); 60 61/** 62 * syscall_get_error - check result of traced system call 63 * @task: task of interest, must be blocked 64 * @regs: task_pt_regs() of @task 65 * 66 * Returns 0 if the system call succeeded, or -ERRORCODE if it failed. 67 * 68 * It's only valid to call this when @task is stopped for tracing on exit 69 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 70 */ 71long syscall_get_error(struct task_struct *task, struct pt_regs *regs); 72 73/** 74 * syscall_get_return_value - get the return value of a traced system call 75 * @task: task of interest, must be blocked 76 * @regs: task_pt_regs() of @task 77 * 78 * Returns the return value of the successful system call. 79 * This value is meaningless if syscall_get_error() returned nonzero. 80 * 81 * It's only valid to call this when @task is stopped for tracing on exit 82 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 83 */ 84long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs); 85 86/** 87 * syscall_set_return_value - change the return value of a traced system call 88 * @task: task of interest, must be blocked 89 * @regs: task_pt_regs() of @task 90 * @error: negative error code, or zero to indicate success 91 * @val: user return value if @error is zero 92 * 93 * This changes the results of the system call that user mode will see. 94 * If @error is zero, the user sees a successful system call with a 95 * return value of @val. If @error is nonzero, it's a negated errno 96 * code; the user sees a failed system call with this errno code. 97 * 98 * It's only valid to call this when @task is stopped for tracing on exit 99 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 100 */ 101void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs, 102 int error, long val); 103 104/** 105 * syscall_get_arguments - extract system call parameter values 106 * @task: task of interest, must be blocked 107 * @regs: task_pt_regs() of @task 108 * @i: argument index [0,5] 109 * @n: number of arguments; n+i must be [1,6]. 110 * @args: array filled with argument values 111 * 112 * Fetches @n arguments to the system call starting with the @i'th argument 113 * (from 0 through 5). Argument @i is stored in @args[0], and so on. 114 * An arch inline version is probably optimal when @i and @n are constants. 115 * 116 * It's only valid to call this when @task is stopped for tracing on 117 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 118 * It's invalid to call this with @i + @n > 6; we only support system calls 119 * taking up to 6 arguments. 120 */ 121void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, 122 unsigned int i, unsigned int n, unsigned long *args); 123 124/** 125 * syscall_set_arguments - change system call parameter value 126 * @task: task of interest, must be in system call entry tracing 127 * @regs: task_pt_regs() of @task 128 * @i: argument index [0,5] 129 * @n: number of arguments; n+i must be [1,6]. 130 * @args: array of argument values to store 131 * 132 * Changes @n arguments to the system call starting with the @i'th argument. 133 * Argument @i gets value @args[0], and so on. 134 * An arch inline version is probably optimal when @i and @n are constants. 135 * 136 * It's only valid to call this when @task is stopped for tracing on 137 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT. 138 * It's invalid to call this with @i + @n > 6; we only support system calls 139 * taking up to 6 arguments. 140 */ 141void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs, 142 unsigned int i, unsigned int n, 143 const unsigned long *args); 144 145#endif /* _ASM_SYSCALL_H */ 146