include/asm-generic/syscall.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Access to user system call parameters and results
   4  *
   5  * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
   6  *
   7  * This file is a stub providing documentation for what functions
   8  * asm-ARCH/syscall.h files need to define.  Most arch definitions
   9  * will be simple inlines.
  10  *
  11  * All of these functions expect to be called with no locks,
  12  * and only when the caller is sure that the task of interest
  13  * cannot return to user mode while we are looking at it.
  14  */
  15
  16 #ifndef _ASM_SYSCALL_H
  17 #define _ASM_SYSCALL_H  1
  18
  19 struct task_struct;
  20 struct pt_regs;
  21
  22 /**
  23  * syscall_get_nr - find what system call a task is executing
  24  * @task:       task of interest, must be blocked
  25  * @regs:       task_pt_regs() of @task
  26  *
  27  * If @task is executing a system call or is at system call
  28  * tracing about to attempt one, returns the system call number.
  29  * If @task is not executing a system call, i.e. it's blocked
  30  * inside the kernel for a fault or signal, returns -1.
  31  *
  32  * Note this returns int even on 64-bit machines.  Only 32 bits of
  33  * system call number can be meaningful.  If the actual arch value
  34  * is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
  35  *
  36  * It's only valid to call this when @task is known to be blocked.
  37  */
  38 int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
  39
  40 /**
  41  * syscall_rollback - roll back registers after an aborted system call
  42  * @task:       task of interest, must be in system call exit tracing
  43  * @regs:       task_pt_regs() of @task
  44  *
  45  * It's only valid to call this when @task is stopped for system
  46  * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
  47  * after tracehook_report_syscall_entry() returned nonzero to prevent
  48  * the system call from taking place.
  49  *
  50  * This rolls back the register state in @regs so it's as if the
  51  * system call instruction was a no-op.  The registers containing
  52  * the system call number and arguments are as they were before the
  53  * system call instruction.  This may not be the same as what the
  54  * register state looked like at system call entry tracing.
  55  */
  56 void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
  57
  58 /**
  59  * syscall_get_error - check result of traced system call
  60  * @task:       task of interest, must be blocked
  61  * @regs:       task_pt_regs() of @task
  62  *
  63  * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
  64  *
  65  * It's only valid to call this when @task is stopped for tracing on exit
  66  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  67  */
  68 long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
  69
  70 /**
  71  * syscall_get_return_value - get the return value of a traced system call
  72  * @task:       task of interest, must be blocked
  73  * @regs:       task_pt_regs() of @task
  74  *
  75  * Returns the return value of the successful system call.
  76  * This value is meaningless if syscall_get_error() returned nonzero.
  77  *
  78  * It's only valid to call this when @task is stopped for tracing on exit
  79  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  80  */
  81 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
  82
  83 /**
  84  * syscall_set_return_value - change the return value of a traced system call
  85  * @task:       task of interest, must be blocked
  86  * @regs:       task_pt_regs() of @task
  87  * @error:      negative error code, or zero to indicate success
  88  * @val:        user return value if @error is zero
  89  *
  90  * This changes the results of the system call that user mode will see.
  91  * If @error is zero, the user sees a successful system call with a
  92  * return value of @val.  If @error is nonzero, it's a negated errno
  93  * code; the user sees a failed system call with this errno code.
  94  *
  95  * It's only valid to call this when @task is stopped for tracing on exit
  96  * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
  97  */
  98 void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  99                               int error, long val);
 100
 101 /**
 102  * syscall_get_arguments - extract system call parameter values
 103  * @task:       task of interest, must be blocked
 104  * @regs:       task_pt_regs() of @task
 105  * @args:       array filled with argument values
 106  *
 107  * Fetches 6 arguments to the system call.  First argument is stored in
 108 *  @args[0], and so on.
 109  *
 110  * It's only valid to call this when @task is stopped for tracing on
 111  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
 112  */
 113 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 114                            unsigned long *args);
 115
 116 /**
 117  * syscall_set_arguments - change system call parameter value
 118  * @task:       task of interest, must be in system call entry tracing
 119  * @regs:       task_pt_regs() of @task
 120  * @args:       array of argument values to store
 121  *
 122  * Changes 6 arguments to the system call.
 123  * The first argument gets value @args[0], and so on.
 124  *
 125  * It's only valid to call this when @task is stopped for tracing on
 126  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
 127  */
 128 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 129                            const unsigned long *args);
 130
 131 /**
 132  * syscall_get_arch - return the AUDIT_ARCH for the current system call
 133  * @task:       task of interest, must be blocked
 134  *
 135  * Returns the AUDIT_ARCH_* based on the system call convention in use.
 136  *
 137  * It's only valid to call this when @task is stopped on entry to a system
 138  * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP.
 139  *
 140  * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
 141  * provide an implementation of this.
 142  */
 143 int syscall_get_arch(struct task_struct *task);
 144 #endif  /* _ASM_SYSCALL_H */