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 %SYSCALL_WORK_SYSCALL_TRACE or
  47  * %SYSCALL_WORK_SYSCALL_AUDIT), after tracehook_report_syscall_entry()
  48  * returned nonzero to prevent 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 %SYSCALL_WORK_SYSCALL_TRACE or
  67  * %SYSCALL_WORK_SYSCALL_AUDIT.
  68  */
  69 long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
  70
  71 /**
  72  * syscall_get_return_value - get the return value of a traced system call
  73  * @task:       task of interest, must be blocked
  74  * @regs:       task_pt_regs() of @task
  75  *
  76  * Returns the return value of the successful system call.
  77  * This value is meaningless if syscall_get_error() returned nonzero.
  78  *
  79  * It's only valid to call this when @task is stopped for tracing on exit
  80  * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
  81  * %SYSCALL_WORK_SYSCALL_AUDIT.
  82  */
  83 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
  84
  85 /**
  86  * syscall_set_return_value - change the return value of a traced system call
  87  * @task:       task of interest, must be blocked
  88  * @regs:       task_pt_regs() of @task
  89  * @error:      negative error code, or zero to indicate success
  90  * @val:        user return value if @error is zero
  91  *
  92  * This changes the results of the system call that user mode will see.
  93  * If @error is zero, the user sees a successful system call with a
  94  * return value of @val.  If @error is nonzero, it's a negated errno
  95  * code; the user sees a failed system call with this errno code.
  96  *
  97  * It's only valid to call this when @task is stopped for tracing on exit
  98  * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
  99  * %SYSCALL_WORK_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  * @args:       array filled with argument values
 109  *
 110  * Fetches 6 arguments to the system call.  First argument is stored in
 111 *  @args[0], and so on.
 112  *
 113  * It's only valid to call this when @task is stopped for tracing on
 114  * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
 115  * %SYSCALL_WORK_SYSCALL_AUDIT.
 116  */
 117 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 118                            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  * @args:       array of argument values to store
 125  *
 126  * Changes 6 arguments to the system call.
 127  * The first argument gets value @args[0], and so on.
 128  *
 129  * It's only valid to call this when @task is stopped for tracing on
 130  * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
 131  * %SYSCALL_WORK_SYSCALL_AUDIT.
 132  */
 133 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
 134                            const unsigned long *args);
 135
 136 /**
 137  * syscall_get_arch - return the AUDIT_ARCH for the current system call
 138  * @task:       task of interest, must be blocked
 139  *
 140  * Returns the AUDIT_ARCH_* based on the system call convention in use.
 141  *
 142  * It's only valid to call this when @task is stopped on entry to a system
 143  * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or
 144  * %SYSCALL_WORK_SECCOMP.
 145  *
 146  * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
 147  * provide an implementation of this.
 148  */
 149 int syscall_get_arch(struct task_struct *task);
 150 #endif  /* _ASM_SYSCALL_H */