include/asm-generic/syscall.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * Access to user system call parameters and results
0004  *
0005  * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
0006  *
0007  * This file is a stub providing documentation for what functions
0008  * asm-ARCH/syscall.h files need to define.  Most arch definitions
0009  * will be simple inlines.
0010  *
0011  * All of these functions expect to be called with no locks,
0012  * and only when the caller is sure that the task of interest
0013  * cannot return to user mode while we are looking at it.
0014  */
0015
0016 #ifndef _ASM_SYSCALL_H
0017 #define _ASM_SYSCALL_H  1
0018
0019 struct task_struct;
0020 struct pt_regs;
0021
0022 /**
0023  * syscall_get_nr - find what system call a task is executing
0024  * @task:   task of interest, must be blocked
0025  * @regs:   task_pt_regs() of @task
0026  *
0027  * If @task is executing a system call or is at system call
0028  * tracing about to attempt one, returns the system call number.
0029  * If @task is not executing a system call, i.e. it's blocked
0030  * inside the kernel for a fault or signal, returns -1.
0031  *
0032  * Note this returns int even on 64-bit machines.  Only 32 bits of
0033  * system call number can be meaningful.  If the actual arch value
0034  * is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
0035  *
0036  * It's only valid to call this when @task is known to be blocked.
0037  */
0038 int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
0039
0040 /**
0041  * syscall_rollback - roll back registers after an aborted system call
0042  * @task:   task of interest, must be in system call exit tracing
0043  * @regs:   task_pt_regs() of @task
0044  *
0045  * It's only valid to call this when @task is stopped for system
0046  * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or
0047  * %SYSCALL_WORK_SYSCALL_AUDIT), after ptrace_report_syscall_entry()
0048  * returned nonzero to prevent the system call from taking place.
0049  *
0050  * This rolls back the register state in @regs so it's as if the
0051  * system call instruction was a no-op.  The registers containing
0052  * the system call number and arguments are as they were before the
0053  * system call instruction.  This may not be the same as what the
0054  * register state looked like at system call entry tracing.
0055  */
0056 void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
0057
0058 /**
0059  * syscall_get_error - check result of traced system call
0060  * @task:   task of interest, must be blocked
0061  * @regs:   task_pt_regs() of @task
0062  *
0063  * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
0064  *
0065  * It's only valid to call this when @task is stopped for tracing on exit
0066  * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
0067  * %SYSCALL_WORK_SYSCALL_AUDIT.
0068  */
0069 long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
0070
0071 /**
0072  * syscall_get_return_value - get the return value of a traced system call
0073  * @task:   task of interest, must be blocked
0074  * @regs:   task_pt_regs() of @task
0075  *
0076  * Returns the return value of the successful system call.
0077  * This value is meaningless if syscall_get_error() returned nonzero.
0078  *
0079  * It's only valid to call this when @task is stopped for tracing on exit
0080  * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
0081  * %SYSCALL_WORK_SYSCALL_AUDIT.
0082  */
0083 long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
0084
0085 /**
0086  * syscall_set_return_value - change the return value of a traced system call
0087  * @task:   task of interest, must be blocked
0088  * @regs:   task_pt_regs() of @task
0089  * @error:  negative error code, or zero to indicate success
0090  * @val:    user return value if @error is zero
0091  *
0092  * This changes the results of the system call that user mode will see.
0093  * If @error is zero, the user sees a successful system call with a
0094  * return value of @val.  If @error is nonzero, it's a negated errno
0095  * code; the user sees a failed system call with this errno code.
0096  *
0097  * It's only valid to call this when @task is stopped for tracing on exit
0098  * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
0099  * %SYSCALL_WORK_SYSCALL_AUDIT.
0100  */
0101 void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
0102                   int error, long val);
0103
0104 /**
0105  * syscall_get_arguments - extract system call parameter values
0106  * @task:   task of interest, must be blocked
0107  * @regs:   task_pt_regs() of @task
0108  * @args:   array filled with argument values
0109  *
0110  * Fetches 6 arguments to the system call.  First argument is stored in
0111 *  @args[0], and so on.
0112  *
0113  * It's only valid to call this when @task is stopped for tracing on
0114  * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
0115  * %SYSCALL_WORK_SYSCALL_AUDIT.
0116  */
0117 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
0118                unsigned long *args);
0119
0120 /**
0121  * syscall_get_arch - return the AUDIT_ARCH for the current system call
0122  * @task:   task of interest, must be blocked
0123  *
0124  * Returns the AUDIT_ARCH_* based on the system call convention in use.
0125  *
0126  * It's only valid to call this when @task is stopped on entry to a system
0127  * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or
0128  * %SYSCALL_WORK_SECCOMP.
0129  *
0130  * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
0131  * provide an implementation of this.
0132  */
0133 int syscall_get_arch(struct task_struct *task);
0134 #endif  /* _ASM_SYSCALL_H */