include/asm-generic/syscall.h

   1 /*
   2  * Access to user system call parameters and results
   3  *
   4  * Copyright (C) 2008 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
  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  *
  35  * It's only valid to call this when @task is known to be blocked.
  36  */
  37 long syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
  38
  39 /**
  40  * syscall_rollback - roll back registers after an aborted system call
  41  * @task:       task of interest, must be in system call exit tracing
  42  * @regs:       task_pt_regs() of @task
  43  *
  44  * It's only valid to call this when @task is stopped for system
  45  * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
  46  * after tracehook_report_syscall_entry() returned nonzero to prevent
  47  * the system call from taking place.
  48  *
  49  * This rolls back the register state in @regs so it's as if the
  50  * system call instruction was a no-op.  The registers containing
  51  * the system call number and arguments are as they were before the
  52  * system call instruction.  This may not be the same as what the
  53  * register state looked like at system call entry tracing.
  54  */
  55 void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
  56
  57 /**
  58  * syscall_get_error - check result of traced system call
  59  * @task:       task of interest, must be blocked
  60  * @regs:       task_pt_regs() of @task
  61  *
  62  * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
  63  *
  64  * It's only valid to call this when @task is stopped for tracing on exit
  65  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  66  */
  67 long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
  68
  69 /**
  70  * syscall_get_return_value - get the return value of a traced system call
  71  * @task:       task of interest, must be blocked
  72  * @regs:       task_pt_regs() of @task
  73  *
  74  * Returns the return value of the successful system call.
  75  * This value is meaningless if syscall_get_error() returned nonzero.
  76  *
  77  * It's only valid to call this when @task is stopped for tracing on exit
  78  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  79  */
  80 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
  81
  82 /**
  83  * syscall_set_return_value - change the return value of a traced system call
  84  * @task:       task of interest, must be blocked
  85  * @regs:       task_pt_regs() of @task
  86  * @error:      negative error code, or zero to indicate success
  87  * @val:        user return value if @error is zero
  88  *
  89  * This changes the results of the system call that user mode will see.
  90  * If @error is zero, the user sees a successful system call with a
  91  * return value of @val.  If @error is nonzero, it's a negated errno
  92  * code; the user sees a failed system call with this errno code.
  93  *
  94  * It's only valid to call this when @task is stopped for tracing on exit
  95  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  96  */
  97 void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  98                               int error, long val);
  99
 100 /**
 101  * syscall_get_arguments - extract system call parameter values
 102  * @task:       task of interest, must be blocked
 103  * @regs:       task_pt_regs() of @task
 104  * @i:          argument index [0,5]
 105  * @n:          number of arguments; n+i must be [1,6].
 106  * @args:       array filled with argument values
 107  *
 108  * Fetches @n arguments to the system call starting with the @i'th argument
 109  * (from 0 through 5).  Argument @i is stored in @args[0], and so on.
 110  * An arch inline version is probably optimal when @i and @n are constants.
 111  *
 112  * It's only valid to call this when @task is stopped for tracing on
 113  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
 114  * It's invalid to call this with @i + @n > 6; we only support system calls
 115  * taking up to 6 arguments.
 116  */
 117 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 118                            unsigned int i, unsigned int n, unsigned long *args);
 119
 120 /**
 121  * syscall_set_arguments - change system call parameter value
 122  * @task:       task of interest, must be in system call entry tracing
 123  * @regs:       task_pt_regs() of @task
 124  * @i:          argument index [0,5]
 125  * @n:          number of arguments; n+i must be [1,6].
 126  * @args:       array of argument values to store
 127  *
 128  * Changes @n arguments to the system call starting with the @i'th argument.
 129  * Argument @i gets value @args[0], and so on.
 130  * An arch inline version is probably optimal when @i and @n are constants.
 131  *
 132  * It's only valid to call this when @task is stopped for tracing on
 133  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
 134  * It's invalid to call this with @i + @n > 6; we only support system calls
 135  * taking up to 6 arguments.
 136  */
 137 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 138                            unsigned int i, unsigned int n,
 139                            const unsigned long *args);
 140
 141 #endif  /* _ASM_SYSCALL_H */