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1 | /* |
2 | * Access to user system call parameters and results | |
3 | * | |
268e4671 | 4 | * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. |
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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 | ||
22 | struct task_struct; | |
23 | struct 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 | * | |
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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 | * | |
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39 | * It's only valid to call this when @task is known to be blocked. |
40 | */ | |
268e4671 | 41 | int syscall_get_nr(struct task_struct *task, struct pt_regs *regs); |
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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 | */ | |
59 | void 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 | */ | |
71 | long 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 | */ | |
84 | long 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 | */ | |
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 | * @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 | */ | |
121 | void 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. | |
22f30168 | 133 | * Argument @i gets value @args[0], and so on. |
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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 | */ | |
141 | void 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 */ |