syscall.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 4 */
 5
 6#include <linux/kernel.h>
 7#include <linux/ptrace.h>
 8#include <linux/seccomp.h>
 9#include <kern_util.h>
10#include <sysdep/ptrace.h>
11#include <sysdep/ptrace_user.h>
12#include <linux/time-internal.h>
13#include <asm/syscall.h>
14#include <asm/unistd.h>
15#include <asm/delay.h>
16
17void handle_syscall(struct uml_pt_regs *r)
18{
19	struct pt_regs *regs = container_of(r, struct pt_regs, regs);
20	int syscall;
21
22	/* Initialize the syscall number and default return value. */
23	UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
24	PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
25
26	if (syscall_trace_enter(regs))
27		goto out;
28
29	/* Do the seccomp check after ptrace; failures should be fast. */
30	if (secure_computing() == -1)
31		goto out;
32
33	syscall = UPT_SYSCALL_NR(r);
34
35	/*
36	 * If no time passes, then sched_yield may not actually yield, causing
37	 * broken spinlock implementations in userspace (ASAN) to hang for long
38	 * periods of time.
39	 */
40	if ((time_travel_mode == TT_MODE_INFCPU ||
41	     time_travel_mode == TT_MODE_EXTERNAL) &&
42	    syscall == __NR_sched_yield)
43		tt_extra_sched_jiffies += 1;
44
45	if (syscall >= 0 && syscall < __NR_syscalls) {
46		unsigned long ret;
47
48		ret = (*sys_call_table[syscall])(UPT_SYSCALL_ARG1(&regs->regs),
49						 UPT_SYSCALL_ARG2(&regs->regs),
50						 UPT_SYSCALL_ARG3(&regs->regs),
51						 UPT_SYSCALL_ARG4(&regs->regs),
52						 UPT_SYSCALL_ARG5(&regs->regs),
53						 UPT_SYSCALL_ARG6(&regs->regs));
54
55		PT_REGS_SET_SYSCALL_RETURN(regs, ret);
56
57		/*
58		 * An error value here can be some form of -ERESTARTSYS
59		 * and then we'd just loop. Make any error syscalls take
60		 * some time, so that it won't just loop if something is
61		 * not ready, and hopefully other things will make some
62		 * progress.
63		 */
64		if (IS_ERR_VALUE(ret) &&
65		    (time_travel_mode == TT_MODE_INFCPU ||
66		     time_travel_mode == TT_MODE_EXTERNAL)) {
67			um_udelay(1);
68			schedule();
69		}
70	}
71
72out:
73	syscall_trace_leave(regs);
74}