syscall.c

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#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/export.h>
#include <asm/syscall.h>

static int collect_syscall(struct task_struct *target, long *callno,
               unsigned long args[6], unsigned int maxargs,
               unsigned long *sp, unsigned long *pc)
{
    struct pt_regs *regs = task_pt_regs(target);
    if (unlikely(!regs))
        return -EAGAIN;

    *sp = user_stack_pointer(regs);
    *pc = instruction_pointer(regs);

    *callno = syscall_get_nr(target, regs);
    if (*callno != -1L && maxargs > 0)
        syscall_get_arguments(target, regs, 0, maxargs, args);

    return 0;
}

int task_current_syscall(struct task_struct *target, long *callno,
             unsigned long args[6], unsigned int maxargs,
             unsigned long *sp, unsigned long *pc)
{
    long state;
    unsigned long ncsw;

    if (unlikely(maxargs > 6))
        return -EINVAL;

    if (target == current)
        return collect_syscall(target, callno, args, maxargs, sp, pc);

    state = target->state;
    if (unlikely(!state))
        return -EAGAIN;

    ncsw = wait_task_inactive(target, state);
    if (unlikely(!ncsw) ||
        unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
        unlikely(wait_task_inactive(target, state) != ncsw))
        return -EAGAIN;

    return 0;
}
EXPORT_SYMBOL_GPL(task_current_syscall);