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
/*
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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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#undef NDEBUG
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#include <assert.h>
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#include <errno.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include "proc.h"
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static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
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{
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uint64_t val1, val2;
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char buf[64], *p;
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ssize_t rv;
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/* save "p < end" checks */
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memset(buf, 0, sizeof(buf));
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rv = pread(fd, buf, sizeof(buf), 0);
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assert(0 <= rv && rv <= sizeof(buf));
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buf[sizeof(buf) - 1] = '\0';
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p = buf;
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val1 = xstrtoull(p, &p);
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assert(p[0] == '.');
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assert('0' <= p[1] && p[1] <= '9');
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assert('0' <= p[2] && p[2] <= '9');
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assert(p[3] == ' ');
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val2 = (p[1] - '0') * 10 + p[2] - '0';
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*uptime = val1 * 100 + val2;
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p += 4;
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val1 = xstrtoull(p, &p);
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assert(p[0] == '.');
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assert('0' <= p[1] && p[1] <= '9');
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assert('0' <= p[2] && p[2] <= '9');
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assert(p[3] == '\n');
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val2 = (p[1] - '0') * 10 + p[2] - '0';
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*idle = val1 * 100 + val2;
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assert(p + 4 == buf + rv);
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}
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