From: David Laight <David.Laight@ACULAB.COM>
To: 'Mathieu Desnoyers' <mathieu.desnoyers@efficios.com>,
Florian Weimer <fweimer@redhat.com>
Cc: carlos <carlos@redhat.com>,
Joseph Myers <joseph@codesourcery.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
libc-alpha <libc-alpha@sourceware.org>,
Thomas Gleixner <tglx@linutronix.de>, Ben Maurer <bmaurer@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Rich Felker <dalias@libc.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: RE: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)
Date: Fri, 14 Jun 2019 13:29:29 +0000 [thread overview]
Message-ID: <69a53ec2ce184af29c4cae58e0b2fb57@AcuMS.aculab.com> (raw)
In-Reply-To: <1085273942.3137.1560517301721.JavaMail.zimbra@efficios.com>
From: Mathieu Desnoyers
> Sent: 14 June 2019 14:02
...
> But my original issue remains: if I define a variable called __rseq_handled
> within either the main executable or the preloaded library, it overshadows
> the libc one:
1) That is the was elf symbol resolution is required to work.
Otherwise variables like 'errno' (non-thread safe form) wouldn't work.
2) Don't do it then :-)
Names starting with __ will be reserved (probably 'for the implementation').
The real 'fun' starts because, under some circumstances, looking up a symbol as:
foo = dlsym(lib_handle, "foo");
Can find the data item instead of the function!
Usually it works (even when foo is global data) because 'lib_handle' refers
to a different symbol table.
But it can go horribly wrong.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-06-14 13:29 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190503184219.19266-1-mathieu.desnoyers@efficios.com>
2019-05-03 18:42 ` Mathieu Desnoyers
2019-05-27 11:19 ` Florian Weimer
2019-05-27 19:27 ` Mathieu Desnoyers
2019-05-29 15:45 ` Mathieu Desnoyers
2019-05-30 20:56 ` Mathieu Desnoyers
2019-05-31 8:06 ` Florian Weimer
2019-05-31 14:48 ` Mathieu Desnoyers
2019-05-31 15:46 ` Florian Weimer
2019-05-31 18:10 ` Mathieu Desnoyers
2019-06-04 11:46 ` Florian Weimer
2019-06-04 15:57 ` Mathieu Desnoyers
2019-06-06 11:57 ` Florian Weimer
2019-06-10 14:43 ` Carlos O'Donell
2019-06-12 14:00 ` Mathieu Desnoyers
2019-06-14 10:03 ` Mathieu Desnoyers
2019-06-14 10:06 ` Florian Weimer
2019-06-14 10:14 ` Mathieu Desnoyers
2019-06-14 11:35 ` Florian Weimer
2019-06-14 12:55 ` Mathieu Desnoyers
2019-06-14 13:01 ` Mathieu Desnoyers
2019-06-14 13:09 ` Florian Weimer
2019-06-14 13:18 ` Mathieu Desnoyers
2019-06-14 13:24 ` Florian Weimer
2019-06-14 13:34 ` Mathieu Desnoyers
2019-06-14 13:42 ` Florian Weimer
2019-06-14 13:47 ` Mathieu Desnoyers
2019-06-14 13:53 ` Florian Weimer
2019-06-14 13:59 ` Mathieu Desnoyers
2019-06-14 13:29 ` David Laight [this message]
2019-06-14 13:39 ` Mathieu Desnoyers
2019-06-12 14:16 ` Mathieu Desnoyers
2019-06-12 14:22 ` Florian Weimer
2019-06-12 14:36 ` Mathieu Desnoyers
2019-06-12 14:43 ` Florian Weimer
2019-05-03 18:42 ` [PATCH 2/5] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux (v4) Mathieu Desnoyers
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