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