linux/include/asm-generic/syscall.h
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   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/**
 146 * syscall_get_arch - return the AUDIT_ARCH for the current system call
 147 * @task:       task of interest, must be in system call entry tracing
 148 * @regs:       task_pt_regs() of @task
 149 *
 150 * Returns the AUDIT_ARCH_* based on the system call convention in use.
 151 *
 152 * It's only valid to call this when @task is stopped on entry to a system
 153 * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
 154 *
 155 * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
 156 * provide an implementation of this.
 157 */
 158int syscall_get_arch(struct task_struct *task, struct pt_regs *regs);
 159#endif  /* _ASM_SYSCALL_H */
 160
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