From: Zev Weiss <zev@bewilderbeest.net>
To: libc-alpha@sourceware.org
Cc: openbmc@lists.ozlabs.org, Wayne Tung <wayne.tung@ui.com>
Subject: nscd time_t size mismatch problem
Date: Tue, 25 Oct 2022 12:54:51 -0700 [thread overview]
Message-ID: <Y1g/C4pinQ1tutC4@hatter.bewilderbeest.net> (raw)
Hello glibc devs,
We've recently been seeing some misbehavior from nscd in OpenBMC. It
manifests as lots of log messages like:
disabled inotify-based monitoring for file /passwd': No such file or directory
stat failed for file /passwd'; will try again later: No such file or directory
disabled inotify-based monitoring for file /group': No such file or directory
stat failed for file /group'; will try again later: No such file or directory
disabled inotify-based monitoring for file /hosts': No such file or directory
stat failed for file /hosts'; will try again later: No such file or directory
disabled inotify-based monitoring for file /resolv.conf': No such file or directory
stat failed for file /resolv.conf'; will try again later: No such file or directory
and so forth. I initially assumed it was a configure-time --sysconfdir
mixup, but after digging into it I found that it actually stems from a
time_t size mismatch (this is a 32-bit ARM gnueabi target):
$ gdb -batch -ex 'pt time_t' -ex 'p sizeof(time_t)' time/time.o
type = long
$1 = 4
$ gdb -batch -ex 'pt time_t' -ex 'p sizeof(time_t)' nscd/nscd.o
type = long long
$1 = 8
The confusing log messages are thus just the result of the coincidence
that sizeof(long long) - sizeof(long) == strlen("/etc"), which causes
the disagreement in the layout of struct traced_file to make it look
like the 'fname' member just had its directory prefix chopped off.
In the discussion of the bug in the OpenBMC issue tracker [0], Wayne
Tung (CCed) came up with the patch below, which does seem to solve the
immediate problem, but if I'm understanding things right does so by just
reverting nscd to a 32-bit time_t, and so I'd expect probably wouldn't
be considered the "right" fix -- however I don't presently know enough
about the 32/64-bit time_t transition and ensuing compatibility concerns
to know what the right fix really is. Should nscd perhaps be using
__time64_t or something instead of time_t?
Thanks,
Zev Weiss
[0] https://github.com/openbmc/openbmc/issues/3881
From 0fda9faf757abd4f5469e6d9207499e97f79a663 Mon Sep 17 00:00:00 2001
From: Wayne Tung <wayne.tung@ui.com>
Date: Thu, 13 Oct 2022 13:10:21 +0800
Subject: [PATCH] Use 32 bits time_t for ncsd
---
Makeconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Makeconfig b/Makeconfig
index 47db08d6ae..f78f7cc74a 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -869,7 +869,7 @@ endif
+extra-math-flags = $(if $(filter libm,$(in-module)),-fno-math-errno,-fmath-errno)
# Use 64 bit time_t support for installed programs
-installed-modules = nonlib nscd lddlibc4 ldconfig locale_programs \
+installed-modules = nonlib lddlibc4 ldconfig locale_programs \
iconvprogs libnss_files libnss_compat libnss_db libnss_hesiod \
libutil libpcprofile libSegFault
+extra-time-flags = $(if $(filter $(installed-modules),\
--
next reply other threads:[~2022-10-25 19:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 19:54 Zev Weiss [this message]
2022-10-25 21:13 ` Adhemerval Zanella Netto
2022-10-26 1:04 ` Zev Weiss
2022-10-26 11:31 ` Adhemerval Zanella Netto
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