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}
75

source code of linux/arch/um/kernel/skas/syscall.c