LXR linux/tools/testing/selftests/proc/read.c

   1/*
   2 * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
   3 *
   4 * Permission to use, copy, modify, and distribute this software for any
   5 * purpose with or without fee is hereby granted, provided that the above
   6 * copyright notice and this permission notice appear in all copies.
   7 *
   8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15 */
  16// Test
  17// 1) read of every file in /proc
  18// 2) readlink of every symlink in /proc
  19// 3) recursively (1) + (2) for every directory in /proc
  20// 4) write to /proc/*/clear_refs and /proc/*/task/*/clear_refs
  21// 5) write to /proc/sysrq-trigger
  22#undef NDEBUG
  23#include <assert.h>
  24#include <errno.h>
  25#include <sys/types.h>
  26#include <dirent.h>
  27#include <stdbool.h>
  28#include <stdlib.h>
  29#include <stdio.h>
  30#include <string.h>
  31#include <sys/stat.h>
  32#include <sys/vfs.h>
  33#include <fcntl.h>
  34#include <unistd.h>
  35
  36#include "proc.h"
  37
  38static void f_reg(DIR *d, const char *filename)
  39{
  40        char buf[4096];
  41        int fd;
  42        ssize_t rv;
  43
  44        /* read from /proc/kmsg can block */
  45        fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
  46        if (fd == -1)
  47                return;
  48        rv = read(fd, buf, sizeof(buf));
  49        assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
  50        close(fd);
  51}
  52
  53static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
  54{
  55        int fd;
  56        ssize_t rv;
  57
  58        fd = openat(dirfd(d), filename, O_WRONLY);
  59        if (fd == -1)
  60                return;
  61        rv = write(fd, buf, len);
  62        assert((0 <= rv && rv <= len) || rv == -1);
  63        close(fd);
  64}
  65
  66static void f_lnk(DIR *d, const char *filename)
  67{
  68        char buf[4096];
  69        ssize_t rv;
  70
  71        rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
  72        assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
  73}
  74
  75static void f(DIR *d, unsigned int level)
  76{
  77        struct dirent *de;
  78
  79        de = xreaddir(d);
  80        assert(de->d_type == DT_DIR);
  81        assert(streq(de->d_name, "."));
  82
  83        de = xreaddir(d);
  84        assert(de->d_type == DT_DIR);
  85        assert(streq(de->d_name, ".."));
  86
  87        while ((de = xreaddir(d))) {
  88                assert(!streq(de->d_name, "."));
  89                assert(!streq(de->d_name, ".."));
  90
  91                switch (de->d_type) {
  92                        DIR *dd;
  93                        int fd;
  94
  95                case DT_REG:
  96                        if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
  97                                f_reg_write(d, de->d_name, "h", 1);
  98                        } else if (level == 1 && streq(de->d_name, "clear_refs")) {
  99                                f_reg_write(d, de->d_name, "1", 1);
 100                        } else if (level == 3 && streq(de->d_name, "clear_refs")) {
 101                                f_reg_write(d, de->d_name, "1", 1);
 102                        } else {
 103                                f_reg(d, de->d_name);
 104                        }
 105                        break;
 106                case DT_DIR:
 107                        fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
 108                        if (fd == -1)
 109                                continue;
 110                        dd = fdopendir(fd);
 111                        if (!dd)
 112                                continue;
 113                        f(dd, level + 1);
 114                        closedir(dd);
 115                        break;
 116                case DT_LNK:
 117                        f_lnk(d, de->d_name);
 118                        break;
 119                default:
 120                        assert(0);
 121                }
 122        }
 123}
 124
 125int main(void)
 126{
 127        DIR *d;
 128        struct statfs sfs;
 129
 130        d = opendir("/proc");
 131        if (!d)
 132                return 4;
 133
 134        /* Ensure /proc is proc. */
 135        if (fstatfs(dirfd(d), &sfs) == -1) {
 136                return 1;
 137        }
 138        if (sfs.f_type != 0x9fa0) {
 139                fprintf(stderr, "error: unexpected f_type %lx\n", (long)sfs.f_type);
 140                return 2;
 141        }
 142
 143        f(d, 0);
 144
 145        return 0;
 146}
 147