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 <sysdep/syscalls.h>
13 #include <linux/time-internal.h>
14 #include <asm/unistd.h>
15 
handle_syscall(struct uml_pt_regs * r)16 void handle_syscall(struct uml_pt_regs *r)
17 {
18 	struct pt_regs *regs = container_of(r, struct pt_regs, regs);
19 	int syscall;
20 
21 	/*
22 	 * If we have infinite CPU resources, then make every syscall also a
23 	 * preemption point, since we don't have any other preemption in this
24 	 * case, and kernel threads would basically never run until userspace
25 	 * went to sleep, even if said userspace interacts with the kernel in
26 	 * various ways.
27 	 */
28 	if (time_travel_mode == TT_MODE_INFCPU ||
29 	    time_travel_mode == TT_MODE_EXTERNAL)
30 		schedule();
31 
32 	/* Initialize the syscall number and default return value. */
33 	UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
34 	PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
35 
36 	if (syscall_trace_enter(regs))
37 		goto out;
38 
39 	/* Do the seccomp check after ptrace; failures should be fast. */
40 	if (secure_computing() == -1)
41 		goto out;
42 
43 	syscall = UPT_SYSCALL_NR(r);
44 	if (syscall >= 0 && syscall < __NR_syscalls)
45 		PT_REGS_SET_SYSCALL_RETURN(regs,
46 				EXECUTE_SYSCALL(syscall, regs));
47 
48 out:
49 	syscall_trace_leave(regs);
50 }
51