include/asm-generic/syscall.h

   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
  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  * 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  */
  41 int 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  */
  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.
 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  */
 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 */