mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-25 20:14:25 +08:00
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>
61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
/*
|
|
* 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.
|
|
*/
|
|
#undef NDEBUG
|
|
#include <assert.h>
|
|
#include <errno.h>
|
|
#include <string.h>
|
|
#include <stdlib.h>
|
|
#include <unistd.h>
|
|
|
|
#include "proc.h"
|
|
|
|
static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
|
|
{
|
|
uint64_t val1, val2;
|
|
char buf[64], *p;
|
|
ssize_t rv;
|
|
|
|
/* save "p < end" checks */
|
|
memset(buf, 0, sizeof(buf));
|
|
rv = pread(fd, buf, sizeof(buf), 0);
|
|
assert(0 <= rv && rv <= sizeof(buf));
|
|
buf[sizeof(buf) - 1] = '\0';
|
|
|
|
p = buf;
|
|
|
|
val1 = xstrtoull(p, &p);
|
|
assert(p[0] == '.');
|
|
assert('0' <= p[1] && p[1] <= '9');
|
|
assert('0' <= p[2] && p[2] <= '9');
|
|
assert(p[3] == ' ');
|
|
|
|
val2 = (p[1] - '0') * 10 + p[2] - '0';
|
|
*uptime = val1 * 100 + val2;
|
|
|
|
p += 4;
|
|
|
|
val1 = xstrtoull(p, &p);
|
|
assert(p[0] == '.');
|
|
assert('0' <= p[1] && p[1] <= '9');
|
|
assert('0' <= p[2] && p[2] <= '9');
|
|
assert(p[3] == '\n');
|
|
|
|
val2 = (p[1] - '0') * 10 + p[2] - '0';
|
|
*idle = val1 * 100 + val2;
|
|
|
|
assert(p + 4 == buf + rv);
|
|
}
|