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 #include <asm/unistd.h>
  15
  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_syscall_max)
  45                 PT_REGS_SET_SYSCALL_RETURN(regs,
  46                                 EXECUTE_SYSCALL(syscall, regs));
  47
  48 out:
  49         syscall_trace_leave(regs);
  50 }