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 ptrace_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