From: Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [RFC] elf: Implement filtering of symbols historically defined in libpthread
Date: Tue, 04 May 2021 14:04:43 +0200 [thread overview]
Message-ID: <87k0oeln6s.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAMe9rOoO3yY3Z1jNU6rYr6uLrNrtUqaj2YbLAc6WFh78E8H1DA@mail.gmail.com> (H. J. Lu's message of "Tue, 4 May 2021 04:47:38 -0700")
* H. J. Lu:
> Since we want to detect the binaries which were linked against glibc
> older than 2.34, we should use the glibc version to check the old
> binaries.
The patch attempts to detect old main programs by looking for the
GLIBC_2.34 symbol version. Since we added __libc_start_main@GLIBC_2.34
(which is called from our version of _start), all standard main programs
linked with glibc 2.34 or later will have this symbol version.
> Of course, we should make a complete list of functions which are
> really implemented in libpthread.so and will be moved to libc.so in
> glibc 2.34.
I'm not sure if it is necessary to do this for *all* symbols. Formally,
a symbol added after glibc 2.0 is not suitable for detecting the
potential multi-threaded nature of a process because the application
could be built for an earlier glibc version, where the symbol is not
available, but pthread_create can still create new threads. The use of
pthread_mutexattr_gettype@@GLIBC_2.1 as the detection symbol does not
follow the rule, of course. With the explicit table approach (as in the
patch), we can add additional lookup symbols later, so I think we can
start out with the GLIBC_2.0 and GLIBC_2.1 symbols plus thrd_exit (the
latter is also used by gnulib for some reason).
Thanks,
Florian
next prev parent reply other threads:[~2021-05-04 12:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 18:01 [RFC] elf: Implement filtering of symbols historically defined in libpthread Florian Weimer via Libc-alpha
2021-05-04 6:55 ` Florian Weimer via Libc-alpha
2021-05-04 11:47 ` H.J. Lu via Libc-alpha
2021-05-04 12:04 ` Florian Weimer via Libc-alpha [this message]
2021-05-04 12:24 ` H.J. Lu via Libc-alpha
2021-05-04 12:27 ` Florian Weimer via Libc-alpha
2021-05-04 12:30 ` H.J. Lu via Libc-alpha
2021-05-04 12:33 ` Florian Weimer via Libc-alpha
2021-05-04 12:36 ` H.J. Lu via Libc-alpha
2021-05-04 12:43 ` Florian Weimer via Libc-alpha
2021-05-04 13:06 ` H.J. Lu via Libc-alpha
2021-05-04 13:13 ` Florian Weimer via Libc-alpha
2021-05-04 13:28 ` H.J. Lu via Libc-alpha
2021-05-04 12:59 ` Adhemerval Zanella via Libc-alpha
2021-05-04 21:08 ` Carlos O'Donell via Libc-alpha
2021-05-04 13:08 ` Andreas Schwab
2021-05-04 16:52 ` Florian Weimer via Libc-alpha
2021-05-04 21:28 ` Carlos O'Donell via Libc-alpha
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