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b2f5de0334
* Test lookup in /proc/self/fd. "map_files" lookup story showed that lookup is not that simple. * Test that all those symlinks open the same file. Check with (st_dev, st_info). * Test that kernel threads do not have anything in their /proc/*/fd/ directory. Now this is where things get interesting. First, kernel threads aren't pinned by /proc/self or equivalent, thus some "atomicity" is required. Second, ->comm can contain whitespace and ')'. No, they are not escaped. Third, the only reliable way to check if process is kernel thread appears to be field #9 in /proc/*/stat. This field is struct task_struct::flags in decimal! Check is done by testing PF_KTHREAD flags like we do in kernel. PF_KTREAD value is a part of userspace ABI !!! Other methods for determining kernel threadness are not reliable: * RSS can be 0 if everything is swapped, even while reading from /proc/self. * ->total_vm CAN BE ZERO if process is finishing munmap(NULL, whole address space); * /proc/*/maps and similar files can be empty because unmapping everything works. Read returning 0 can't distinguish between kernel thread and such suicide process. Link: http://lkml.kernel.org/r/20180505000414.GA15090@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
133 lines
3.1 KiB
C
133 lines
3.1 KiB
C
/*
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* Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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// Test
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// 1) read of every file in /proc
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// 2) readlink of every symlink in /proc
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// 3) recursively (1) + (2) for every directory in /proc
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// 4) write to /proc/*/clear_refs and /proc/*/task/*/clear_refs
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// 5) write to /proc/sysrq-trigger
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#undef NDEBUG
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#include <assert.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <dirent.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include "proc.h"
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static void f_reg(DIR *d, const char *filename)
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{
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char buf[4096];
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int fd;
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ssize_t rv;
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/* read from /proc/kmsg can block */
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fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
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if (fd == -1)
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return;
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rv = read(fd, buf, sizeof(buf));
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assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
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close(fd);
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}
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static void f_reg_write(DIR *d, const char *filename, const char *buf, size_t len)
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{
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int fd;
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ssize_t rv;
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fd = openat(dirfd(d), filename, O_WRONLY);
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if (fd == -1)
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return;
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rv = write(fd, buf, len);
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assert((0 <= rv && rv <= len) || rv == -1);
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close(fd);
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}
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static void f_lnk(DIR *d, const char *filename)
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{
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char buf[4096];
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ssize_t rv;
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rv = readlinkat(dirfd(d), filename, buf, sizeof(buf));
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assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
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}
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static void f(DIR *d, unsigned int level)
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{
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struct dirent *de;
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de = xreaddir(d);
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assert(de->d_type == DT_DIR);
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assert(streq(de->d_name, "."));
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de = xreaddir(d);
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assert(de->d_type == DT_DIR);
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assert(streq(de->d_name, ".."));
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while ((de = xreaddir(d))) {
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assert(!streq(de->d_name, "."));
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assert(!streq(de->d_name, ".."));
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switch (de->d_type) {
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DIR *dd;
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int fd;
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case DT_REG:
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if (level == 0 && streq(de->d_name, "sysrq-trigger")) {
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f_reg_write(d, de->d_name, "h", 1);
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} else if (level == 1 && streq(de->d_name, "clear_refs")) {
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f_reg_write(d, de->d_name, "1", 1);
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} else if (level == 3 && streq(de->d_name, "clear_refs")) {
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f_reg_write(d, de->d_name, "1", 1);
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} else {
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f_reg(d, de->d_name);
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}
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break;
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case DT_DIR:
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fd = openat(dirfd(d), de->d_name, O_DIRECTORY|O_RDONLY);
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if (fd == -1)
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continue;
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dd = fdopendir(fd);
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if (!dd)
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continue;
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f(dd, level + 1);
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closedir(dd);
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break;
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case DT_LNK:
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f_lnk(d, de->d_name);
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break;
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default:
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assert(0);
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}
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}
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}
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int main(void)
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{
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DIR *d;
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d = opendir("/proc");
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if (!d)
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return 2;
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f(d, 0);
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return 0;
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}
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