linux/lib/syscall.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/export.h>
#include <asm/syscall.h>

static int collect_syscall(struct task_struct *target, struct syscall_info *info)
{ … }

/**
 * task_current_syscall - Discover what a blocked task is doing.
 * @target:		thread to examine
 * @info:		structure with the following fields:
 *			 .sp        - filled with user stack pointer
 *			 .data.nr   - filled with system call number or -1
 *			 .data.args - filled with @maxargs system call arguments
 *			 .data.instruction_pointer - filled with user PC
 *
 * If @target is blocked in a system call, returns zero with @info.data.nr
 * set to the call's number and @info.data.args filled in with its
 * arguments. Registers not used for system call arguments may not be available
 * and it is not kosher to use &struct user_regset calls while the system
 * call is still in progress.  Note we may get this result if @target
 * has finished its system call but not yet returned to user mode, such
 * as when it's stopped for signal handling or syscall exit tracing.
 *
 * If @target is blocked in the kernel during a fault or exception,
 * returns zero with *@info.data.nr set to -1 and does not fill in
 * @info.data.args. If so, it's now safe to examine @target using
 * &struct user_regset get() calls as long as we're sure @target won't return
 * to user mode.
 *
 * Returns -%EAGAIN if @target does not remain blocked.
 */
int task_current_syscall(struct task_struct *target, struct syscall_info *info)
{ … }