| 1 | |
| 2 | * Access to user system call parameters and results
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| 3 | *
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| 4 | * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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| 5 | *
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| 6 | * This copyrighted material is made available to anyone wishing to use,
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| 7 | * modify, copy, or redistribute it subject to the terms and conditions
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| 8 | * of the GNU General Public License v.2.
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| 9 | *
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| 10 | * This file is a stub providing documentation for what functions
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| 11 | * asm-ARCH/syscall.h files need to define. Most arch definitions
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| 12 | * will be simple inlines.
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| 13 | *
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| 14 | * All of these functions expect to be called with no locks,
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| 15 | * and only when the caller is sure that the task of interest
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| 16 | * cannot return to user mode while we are looking at it.
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| 17 |
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| 18 |
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| 19 | #ifndef _ASM_SYSCALL_H
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| 20 | #define _ASM_SYSCALL_H 1
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| 21 |
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| 22 | struct task_struct;
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| 23 | struct pt_regs;
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| 24 |
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| 25 | |
| 26 | * syscall_get_nr - find what system call a task is executing
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| 27 | * @task: task of interest, must be blocked
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| 28 | * @regs: task_pt_regs() of @task
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| 29 | *
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| 30 | * If @task is executing a system call or is at system call
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| 31 | * tracing about to attempt one, returns the system call number.
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| 32 | * If @task is not executing a system call, i.e. it's blocked
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| 33 | * inside the kernel for a fault or signal, returns -1.
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| 34 | *
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| 35 | * Note this returns int even on 64-bit machines. Only 32 bits of
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| 36 | * system call number can be meaningful. If the actual arch value
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| 37 | * is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
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| 38 | *
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| 39 | * It's only valid to call this when @task is known to be blocked.
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| 40 |
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| 41 | int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
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| 42 |
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| 43 | |
| 44 | * syscall_rollback - roll back registers after an aborted system call
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| 45 | * @task: task of interest, must be in system call exit tracing
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| 46 | * @regs: task_pt_regs() of @task
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| 47 | *
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| 48 | * It's only valid to call this when @task is stopped for system
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| 49 | * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
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| 50 | * after tracehook_report_syscall_entry() returned nonzero to prevent
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| 51 | * the system call from taking place.
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| 52 | *
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| 53 | * This rolls back the register state in @regs so it's as if the
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| 54 | * system call instruction was a no-op. The registers containing
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| 55 | * the system call number and arguments are as they were before the
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| 56 | * system call instruction. This may not be the same as what the
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| 57 | * register state looked like at system call entry tracing.
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| 58 |
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| 59 | void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
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| 60 |
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| 61 | |
| 62 | * syscall_get_error - check result of traced system call
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| 63 | * @task: task of interest, must be blocked
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| 64 | * @regs: task_pt_regs() of @task
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| 65 | *
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| 66 | * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
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| 67 | *
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| 68 | * It's only valid to call this when @task is stopped for tracing on exit
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| 69 | * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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| 70 |
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| 71 | long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
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| 72 |
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| 73 | |
| 74 | * syscall_get_return_value - get the return value of a traced system call
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| 75 | * @task: task of interest, must be blocked
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| 76 | * @regs: task_pt_regs() of @task
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| 77 | *
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| 78 | * Returns the return value of the successful system call.
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| 79 | * This value is meaningless if syscall_get_error() returned nonzero.
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| 80 | *
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| 81 | * It's only valid to call this when @task is stopped for tracing on exit
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| 82 | * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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| 83 |
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| 84 | long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
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| 85 |
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| 86 | |
| 87 | * syscall_set_return_value - change the return value of a traced system call
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| 88 | * @task: task of interest, must be blocked
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| 89 | * @regs: task_pt_regs() of @task
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| 90 | * @error: negative error code, or zero to indicate success
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| 91 | * @val: user return value if @error is zero
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| 92 | *
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| 93 | * This changes the results of the system call that user mode will see.
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| 94 | * If @error is zero, the user sees a successful system call with a
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| 95 | * return value of @val. If @error is nonzero, it's a negated errno
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| 96 | * code; the user sees a failed system call with this errno code.
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| 97 | *
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| 98 | * It's only valid to call this when @task is stopped for tracing on exit
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| 99 | * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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| 100 |
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| 101 | void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
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| 102 | int error, long val);
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| 103 |
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| 104 | |
| 105 | * syscall_get_arguments - extract system call parameter values
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| 106 | * @task: task of interest, must be blocked
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| 107 | * @regs: task_pt_regs() of @task
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| 108 | * @i: argument index [0,5]
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| 109 | * @n: number of arguments; n+i must be [1,6].
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| 110 | * @args: array filled with argument values
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| 111 | *
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| 112 | * Fetches @n arguments to the system call starting with the @i'th argument
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| 113 | * (from 0 through 5). Argument @i is stored in @args[0], and so on.
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| 114 | * An arch inline version is probably optimal when @i and @n are constants.
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| 115 | *
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| 116 | * It's only valid to call this when @task is stopped for tracing on
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| 117 | * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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| 118 | * It's invalid to call this with @i + @n > 6; we only support system calls
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| 119 | * taking up to 6 arguments.
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| 120 |
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| 121 | void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
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| 122 | unsigned int i, unsigned int n, unsigned long *args);
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| 123 |
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| 124 | |
| 125 | * syscall_set_arguments - change system call parameter value
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| 126 | * @task: task of interest, must be in system call entry tracing
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| 127 | * @regs: task_pt_regs() of @task
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| 128 | * @i: argument index [0,5]
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| 129 | * @n: number of arguments; n+i must be [1,6].
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| 130 | * @args: array of argument values to store
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| 131 | *
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| 132 | * Changes @n arguments to the system call starting with the @i'th argument.
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| 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.
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| 135 | *
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| 136 | * It's only valid to call this when @task is stopped for tracing on
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| 137 | * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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| 138 | * It's invalid to call this with @i + @n > 6; we only support system calls
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| 139 | * taking up to 6 arguments.
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| 140 |
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| 141 | void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
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| 142 | unsigned int i, unsigned int n,
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| 143 | const unsigned long *args);
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| 144 |
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| 145 | #endif
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