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 %SYSCALL_WORK_SYSCALL_TRACE or 47 * %SYSCALL_WORK_SYSCALL_AUDIT), after tracehook_report_syscall_entry() 48 * returned nonzero to prevent 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 %SYSCALL_WORK_SYSCALL_TRACE or 67 * %SYSCALL_WORK_SYSCALL_AUDIT. 68 */ 69 long syscall_get_error(struct task_struct *task, struct pt_regs *regs); 70 71 /** 72 * syscall_get_return_value - get the return value of a traced system call 73 * @task: task of interest, must be blocked 74 * @regs: task_pt_regs() of @task 75 * 76 * Returns the return value of the successful system call. 77 * This value is meaningless if syscall_get_error() returned nonzero. 78 * 79 * It's only valid to call this when @task is stopped for tracing on exit 80 * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or 81 * %SYSCALL_WORK_SYSCALL_AUDIT. 82 */ 83 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs); 84 85 /** 86 * syscall_set_return_value - change the return value of a traced system call 87 * @task: task of interest, must be blocked 88 * @regs: task_pt_regs() of @task 89 * @error: negative error code, or zero to indicate success 90 * @val: user return value if @error is zero 91 * 92 * This changes the results of the system call that user mode will see. 93 * If @error is zero, the user sees a successful system call with a 94 * return value of @val. If @error is nonzero, it's a negated errno 95 * code; the user sees a failed system call with this errno code. 96 * 97 * It's only valid to call this when @task is stopped for tracing on exit 98 * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or 99 * %SYSCALL_WORK_SYSCALL_AUDIT. 100 */ 101 void 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 * @args: array filled with argument values 109 * 110 * Fetches 6 arguments to the system call. First argument is stored in 111 * @args[0], and so on. 112 * 113 * It's only valid to call this when @task is stopped for tracing on 114 * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or 115 * %SYSCALL_WORK_SYSCALL_AUDIT. 116 */ 117 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, 118 unsigned long *args); 119 120 /** 121 * syscall_get_arch - return the AUDIT_ARCH for the current system call 122 * @task: task of interest, must be blocked 123 * 124 * Returns the AUDIT_ARCH_* based on the system call convention in use. 125 * 126 * It's only valid to call this when @task is stopped on entry to a system 127 * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or 128 * %SYSCALL_WORK_SECCOMP. 129 * 130 * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must 131 * provide an implementation of this. 132 */ 133 int syscall_get_arch(struct task_struct *task); 134 #endif /* _ASM_SYSCALL_H */ 135