process.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015 Thomas Meyer ([email protected])
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <asm/unistd.h>
#include <init.h>
#include <longjmp.h>
#include <os.h>
#include <skas/skas.h>

void os_alarm_process(int pid)
{
	if (pid <= 0)
		return;

	kill(pid, SIGALRM);
}

void os_kill_process(int pid, int reap_child)
{
	if (pid <= 0)
		return;

	/* Block signals until child is reaped */
	block_signals();

	kill(pid, SIGKILL);
	if (reap_child)
		CATCH_EINTR(waitpid(pid, NULL, __WALL));

	unblock_signals();
}

/* Kill off a ptraced child by all means available.  kill it normally first,
 * then PTRACE_KILL it, then PTRACE_CONT it in case it's in a run state from
 * which it can't exit directly.
 */

void os_kill_ptraced_process(int pid, int reap_child)
{
	if (pid <= 0)
		return;

	/* Block signals until child is reaped */
	block_signals();

	kill(pid, SIGKILL);
	ptrace(PTRACE_KILL, pid);
	ptrace(PTRACE_CONT, pid);
	if (reap_child)
		CATCH_EINTR(waitpid(pid, NULL, __WALL));

	unblock_signals();
}

pid_t os_reap_child(void)
{
	int status;

	/* Try to reap a child */
	return waitpid(-1, &status, WNOHANG);
}

/* Don't use the glibc version, which caches the result in TLS. It misses some
 * syscalls, and also breaks with clone(), which does not unshare the TLS.
 */

int os_getpid(void)
{
	return syscall(__NR_getpid);
}

int os_map_memory(void *virt, int fd, unsigned long long off, unsigned long len,
		  int r, int w, int x)
{
	void *loc;
	int prot;

	prot = (r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) |
		(x ? PROT_EXEC : 0);

	loc = mmap64((void *) virt, len, prot, MAP_SHARED | MAP_FIXED,
		     fd, off);
	if (loc == MAP_FAILED)
		return -errno;
	return 0;
}

int os_protect_memory(void *addr, unsigned long len, int r, int w, int x)
{
	int prot = ((r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) |
		    (x ? PROT_EXEC : 0));

	if (mprotect(addr, len, prot) < 0)
		return -errno;

	return 0;
}

int os_unmap_memory(void *addr, int len)
{
	int err;

	err = munmap(addr, len);
	if (err < 0)
		return -errno;
	return 0;
}

#ifndef MADV_REMOVE
#define MADV_REMOVE KERNEL_MADV_REMOVE
#endif

int os_drop_memory(void *addr, int length)
{
	int err;

	err = madvise(addr, length, MADV_REMOVE);
	if (err < 0)
		err = -errno;
	return err;
}

int __init can_drop_memory(void)
{
	void *addr;
	int fd, ok = 0;

	printk(UM_KERN_INFO "Checking host MADV_REMOVE support...");
	fd = create_mem_file(UM_KERN_PAGE_SIZE);
	if (fd < 0) {
		printk(UM_KERN_ERR "Creating test memory file failed, "
		       "err = %d\n", -fd);
		goto out;
	}

	addr = mmap64(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
		      MAP_SHARED, fd, 0);
	if (addr == MAP_FAILED) {
		printk(UM_KERN_ERR "Mapping test memory file failed, "
		       "err = %d\n", -errno);
		goto out_close;
	}

	if (madvise(addr, UM_KERN_PAGE_SIZE, MADV_REMOVE) != 0) {
		printk(UM_KERN_ERR "MADV_REMOVE failed, err = %d\n", -errno);
		goto out_unmap;
	}

	printk(UM_KERN_CONT "OK\n");
	ok = 1;

out_unmap:
	munmap(addr, UM_KERN_PAGE_SIZE);
out_close:
	close(fd);
out:
	return ok;
}

void init_new_thread_signals(void)
{
	set_handler(SIGSEGV);
	set_handler(SIGTRAP);
	set_handler(SIGFPE);
	set_handler(SIGILL);
	set_handler(SIGBUS);
	signal(SIGHUP, SIG_IGN);
	set_handler(SIGIO);
	/* We (currently) only use the child reaper IRQ in seccomp mode */
	if (using_seccomp)
		set_handler(SIGCHLD);
	signal(SIGWINCH, SIG_IGN);
}

void os_set_pdeathsig(void)
{
	prctl(PR_SET_PDEATHSIG, SIGKILL);
}