proc: test /proc/thread-self symlink

2018-08-22T17:52:45+00:00

Same story: I have WIP patch to make it faster, so better have a test as well. Link: http://lkml.kernel.org/r/20180627195209.GC18113@avx2 Signed-off-by: Alexey Dobriyan Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: test /proc/self symlink

2018-08-22T17:52:45+00:00

There are plans to change how /proc/self result is calculated, for that a test is necessary. Use direct system call because of this whole getpid caching story. Link: http://lkml.kernel.org/r/20180627195103.GB18113@avx2 Signed-off-by: Alexey Dobriyan Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

tools/testing/selftests/proc: test /proc/*/fd a bit (+ PF_KTHREAD is ABI!)

2018-06-08T00:34:38+00:00

* 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/linux.git/tools/testing/selftests/proc/proc.h, branch v6.19.11

proc: test /proc/thread-self symlink

proc: test /proc/self symlink

tools/testing/selftests/proc: test /proc/*/fd a bit (+ PF_KTHREAD is ABI!)