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kernel/linux-imx6_3.14.28/include/asm-generic/syscall.h 6.31 KB
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  /*
   * Access to user system call parameters and results
   *
   * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions
   * of the GNU General Public License v.2.
   *
   * This file is a stub providing documentation for what functions
   * asm-ARCH/syscall.h files need to define.  Most arch definitions
   * will be simple inlines.
   *
   * All of these functions expect to be called with no locks,
   * and only when the caller is sure that the task of interest
   * cannot return to user mode while we are looking at it.
   */
  
  #ifndef _ASM_SYSCALL_H
  #define _ASM_SYSCALL_H	1
  
  struct task_struct;
  struct pt_regs;
  
  /**
   * syscall_get_nr - find what system call a task is executing
   * @task:	task of interest, must be blocked
   * @regs:	task_pt_regs() of @task
   *
   * If @task is executing a system call or is at system call
   * tracing about to attempt one, returns the system call number.
   * If @task is not executing a system call, i.e. it's blocked
   * inside the kernel for a fault or signal, returns -1.
   *
   * Note this returns int even on 64-bit machines.  Only 32 bits of
   * system call number can be meaningful.  If the actual arch value
   * is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
   *
   * It's only valid to call this when @task is known to be blocked.
   */
  int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
  
  /**
   * syscall_rollback - roll back registers after an aborted system call
   * @task:	task of interest, must be in system call exit tracing
   * @regs:	task_pt_regs() of @task
   *
   * It's only valid to call this when @task is stopped for system
   * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
   * after tracehook_report_syscall_entry() returned nonzero to prevent
   * the system call from taking place.
   *
   * This rolls back the register state in @regs so it's as if the
   * system call instruction was a no-op.  The registers containing
   * the system call number and arguments are as they were before the
   * system call instruction.  This may not be the same as what the
   * register state looked like at system call entry tracing.
   */
  void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
  
  /**
   * syscall_get_error - check result of traced system call
   * @task:	task of interest, must be blocked
   * @regs:	task_pt_regs() of @task
   *
   * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
   *
   * It's only valid to call this when @task is stopped for tracing on exit
   * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
   */
  long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
  
  /**
   * syscall_get_return_value - get the return value of a traced system call
   * @task:	task of interest, must be blocked
   * @regs:	task_pt_regs() of @task
   *
   * Returns the return value of the successful system call.
   * This value is meaningless if syscall_get_error() returned nonzero.
   *
   * It's only valid to call this when @task is stopped for tracing on exit
   * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
   */
  long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
  
  /**
   * syscall_set_return_value - change the return value of a traced system call
   * @task:	task of interest, must be blocked
   * @regs:	task_pt_regs() of @task
   * @error:	negative error code, or zero to indicate success
   * @val:	user return value if @error is zero
   *
   * This changes the results of the system call that user mode will see.
   * If @error is zero, the user sees a successful system call with a
   * return value of @val.  If @error is nonzero, it's a negated errno
   * code; the user sees a failed system call with this errno code.
   *
   * It's only valid to call this when @task is stopped for tracing on exit
   * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
   */
  void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  			      int error, long val);
  
  /**
   * syscall_get_arguments - extract system call parameter values
   * @task:	task of interest, must be blocked
   * @regs:	task_pt_regs() of @task
   * @i:		argument index [0,5]
   * @n:		number of arguments; n+i must be [1,6].
   * @args:	array filled with argument values
   *
   * Fetches @n arguments to the system call starting with the @i'th argument
   * (from 0 through 5).  Argument @i is stored in @args[0], and so on.
   * An arch inline version is probably optimal when @i and @n are constants.
   *
   * It's only valid to call this when @task is stopped for tracing on
   * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
   * It's invalid to call this with @i + @n > 6; we only support system calls
   * taking up to 6 arguments.
   */
  void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  			   unsigned int i, unsigned int n, unsigned long *args);
  
  /**
   * syscall_set_arguments - change system call parameter value
   * @task:	task of interest, must be in system call entry tracing
   * @regs:	task_pt_regs() of @task
   * @i:		argument index [0,5]
   * @n:		number of arguments; n+i must be [1,6].
   * @args:	array of argument values to store
   *
   * Changes @n arguments to the system call starting with the @i'th argument.
   * Argument @i gets value @args[0], and so on.
   * An arch inline version is probably optimal when @i and @n are constants.
   *
   * It's only valid to call this when @task is stopped for tracing on
   * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
   * It's invalid to call this with @i + @n > 6; we only support system calls
   * taking up to 6 arguments.
   */
  void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
  			   unsigned int i, unsigned int n,
  			   const unsigned long *args);
  
  /**
   * syscall_get_arch - return the AUDIT_ARCH for the current system call
   * @task:	task of interest, must be in system call entry tracing
   * @regs:	task_pt_regs() of @task
   *
   * Returns the AUDIT_ARCH_* based on the system call convention in use.
   *
   * It's only valid to call this when @task is stopped on entry to a system
   * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
   *
   * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
   * provide an implementation of this.
   */
  int syscall_get_arch(struct task_struct *task, struct pt_regs *regs);
  #endif	/* _ASM_SYSCALL_H */