From b2f5de0334f03e90ae7dee72a7fc597ef555a9a8 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Thu, 7 Jun 2018 17:10:20 -0700 Subject: tools/testing/selftests/proc: test /proc/*/fd a bit (+ PF_KTHREAD is ABI!) * 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 --- tools/testing/selftests/proc/read.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-) (limited to 'tools/testing/selftests/proc/read.c') diff --git a/tools/testing/selftests/proc/read.c b/tools/testing/selftests/proc/read.c index 1e73c2232097..563e752e6eba 100644 --- a/tools/testing/selftests/proc/read.c +++ b/tools/testing/selftests/proc/read.c @@ -31,22 +31,7 @@ #include #include -static inline bool streq(const char *s1, const char *s2) -{ - return strcmp(s1, s2) == 0; -} - -static struct dirent *xreaddir(DIR *d) -{ - struct dirent *de; - - errno = 0; - de = readdir(d); - if (!de && errno != 0) { - exit(1); - } - return de; -} +#include "proc.h" static void f_reg(DIR *d, const char *filename) { -- cgit v1.2.3