Orange Pi5 kernel

/*
 * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
// Test that /proc/$KERNEL_THREAD/fd/ is empty.
 
#undef NDEBUG
#include <sys/syscall.h>
#include <assert.h>
#include <dirent.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
 
#include "proc.h"
 
#define PF_KHTREAD 0x00200000
 
/*
 * Test for kernel threadness atomically with openat().
 *
 * Return /proc/$PID/fd descriptor if process is kernel thread.
 * Return -1 if a process is userspace process.
 */
static int kernel_thread_fd(unsigned int pid)
{
<------>unsigned int flags = 0;
<------>char buf[4096];
<------>int dir_fd, fd;
<------>ssize_t rv;
 
<------>snprintf(buf, sizeof(buf), "/proc/%u", pid);
<------>dir_fd = open(buf, O_RDONLY|O_DIRECTORY);
<------>if (dir_fd == -1)
<------><------>return -1;
 
<------>/*
<------> * Believe it or not, struct task_struct::flags is directly exposed
<------> * to userspace!
<------> */
<------>fd = openat(dir_fd, "stat", O_RDONLY);
<------>if (fd == -1) {
<------><------>close(dir_fd);
<------><------>return -1;
<------>}
<------>rv = read(fd, buf, sizeof(buf));
<------>close(fd);
<------>if (0 < rv && rv <= sizeof(buf)) {
<------><------>unsigned long long flags_ull;
<------><------>char *p, *end;
<------><------>int i;
 
<------><------>assert(buf[rv - 1] == '\n');
<------><------>buf[rv - 1] = '\0';
 
<------><------>/* Search backwards: ->comm can contain whitespace and ')'. */
<------><------>for (i = 0; i < 43; i++) {
<------><------><------>p = strrchr(buf, ' ');
<------><------><------>assert(p);
<------><------><------>*p = '\0';
<------><------>}
 
<------><------>p = strrchr(buf, ' ');
<------><------>assert(p);
 
<------><------>flags_ull = xstrtoull(p + 1, &end);
<------><------>assert(*end == '\0');
<------><------>assert(flags_ull == (unsigned int)flags_ull);
 
<------><------>flags = flags_ull;
<------>}
 
<------>fd = -1;
<------>if (flags & PF_KHTREAD) {
<------><------>fd = openat(dir_fd, "fd", O_RDONLY|O_DIRECTORY);
<------>}
<------>close(dir_fd);
<------>return fd;
}
 
static void test_readdir(int fd)
{
<------>DIR *d;
<------>struct dirent *de;
 
<------>d = fdopendir(fd);
<------>assert(d);
 
<------>de = xreaddir(d);
<------>assert(streq(de->d_name, "."));
<------>assert(de->d_type == DT_DIR);
 
<------>de = xreaddir(d);
<------>assert(streq(de->d_name, ".."));
<------>assert(de->d_type == DT_DIR);
 
<------>de = xreaddir(d);
<------>assert(!de);
}
 
static inline int sys_statx(int dirfd, const char *pathname, int flags,
<------><------><------>    unsigned int mask, void *stx)
{
<------>return syscall(SYS_statx, dirfd, pathname, flags, mask, stx);
}
 
static void test_lookup_fail(int fd, const char *pathname)
{
<------>char stx[256] __attribute__((aligned(8)));
<------>int rv;
 
<------>rv = sys_statx(fd, pathname, AT_SYMLINK_NOFOLLOW, 0, (void *)stx);
<------>assert(rv == -1 && errno == ENOENT);
}
 
static void test_lookup(int fd)
{
<------>char buf[64];
<------>unsigned int u;
<------>int i;
 
<------>for (i = INT_MIN; i < INT_MIN + 1024; i++) {
<------><------>snprintf(buf, sizeof(buf), "%d", i);
<------><------>test_lookup_fail(fd, buf);
<------>}
<------>for (i = -1024; i < 1024; i++) {
<------><------>snprintf(buf, sizeof(buf), "%d", i);
<------><------>test_lookup_fail(fd, buf);
<------>}
<------>for (u = INT_MAX - 1024; u < (unsigned int)INT_MAX + 1024; u++) {
<------><------>snprintf(buf, sizeof(buf), "%u", u);
<------><------>test_lookup_fail(fd, buf);
<------>}
<------>for (u = UINT_MAX - 1024; u != 0; u++) {
<------><------>snprintf(buf, sizeof(buf), "%u", u);
<------><------>test_lookup_fail(fd, buf);
<------>}
}
 
int main(void)
{
<------>unsigned int pid;
<------>int fd;
 
<------>/*
<------> * In theory this will loop indefinitely if kernel threads are exiled
<------> * from /proc.
<------> *
<------> * Start with kthreadd.
<------> */
<------>pid = 2;
<------>while ((fd = kernel_thread_fd(pid)) == -1 && pid < 1024) {
<------><------>pid++;
<------>}
<------>/* EACCES if run as non-root. */
<------>if (pid >= 1024)
<------><------>return 1;
 
<------>test_readdir(fd);
<------>test_lookup(fd);
 
<------>return 0;
}