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pidfd-util: introduce pidfd_info_mask_is_supported() helper function

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Since kernel v6.19, ioctl(PIDFD_GET_INFO) can return the set of
supported flags when PIDFD_INFO_SUPPORTED_MASK is specified.

This allows checking whether, e.g., PIDFD_INFO_COREDUMP_SIGNAL is
supported by the running kernel.
This commit is contained in:
Yu Watanabe
2026-08-15 01:35:23 +09:00
parent 73e67f5fb1
commit 7ae2bc9199
3 changed files with 84 additions and 0 deletions
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src/test/test-pidfd-util.c
+41
View File
@@ -21,4 +21,45 @@ TEST(pidfd_get_inode_id_self_cached) {
}
}
TEST(pidfd_info_mask_is_supported) {
int r;
r = pidfd_info_mask_is_supported(PIDFD_INFO_PID | PIDFD_INFO_CREDS | PIDFD_INFO_CGROUPID);
if (r > 0)
log_info("PIDFD_INFO_PID, PIDFD_INFO_CREDS, and PIDFD_INFO_CGROUPID are supported.");
else {
ASSERT_ERROR(r, EOPNOTSUPP);
log_info("ioctl(PIDFD_GET_INFO) is not supported. Maybe the kernel is older than v6.13.");
}
/* The flag PIDFD_INFO_EXIT itself is supported since v6.15, but we have no way to check if it is
* supported without PIDFD_INFO_SUPPORTED_MASK (since v6.19) (or, of course, we can check it by
* terminating a process...). */
if (ASSERT_OK_OR(pidfd_info_mask_is_supported(PIDFD_INFO_EXIT), -EOPNOTSUPP) > 0)
log_info("PIDFD_INFO_EXIT is supported.");
else
log_info("PIDFD_INFO_EXIT is not supported. Maybe the kernel is older than v6.19.");
/* Similar here. The flag PIDFD_INFO_COREDUMP itself is supported since v6.16. */
if (ASSERT_OK_OR(pidfd_info_mask_is_supported(PIDFD_INFO_COREDUMP), -EOPNOTSUPP) > 0)
log_info("PIDFD_INFO_COREDUMP is supported.");
else
log_info("PIDFD_INFO_COREDUMP is not supported. Maybe the kernel is older than v6.19.");
if (ASSERT_OK_OR(pidfd_info_mask_is_supported(PIDFD_INFO_SUPPORTED_MASK), -EOPNOTSUPP) > 0)
log_info("PIDFD_INFO_SUPPORTED_MASK is supported.");
else
log_info("PIDFD_INFO_SUPPORTED_MASK is not supported. Maybe the kernel is older than v6.19.");
if (ASSERT_OK_OR(pidfd_info_mask_is_supported(PIDFD_INFO_COREDUMP_SIGNAL), -EOPNOTSUPP) > 0)
log_info("PIDFD_INFO_COREDUMP_SIGNAL is supported.");
else
log_info("PIDFD_INFO_COREDUMP_SIGNAL is not supported. Maybe the kernel is older than v6.19.");
if (ASSERT_OK_OR(pidfd_info_mask_is_supported(PIDFD_INFO_COREDUMP_CODE), -EOPNOTSUPP) > 0)
log_info("PIDFD_INFO_COREDUMP_CODE is supported.");
else
log_info("PIDFD_INFO_COREDUMP_CODE is not supported. Maybe the kernel is older than v7.1.");
}
DEFINE_TEST_MAIN(LOG_DEBUG);