This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)
- From: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: carlos <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, Rich Felker <dalias at libc dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Mon, 14 Jan 2019 15:27:28 -0500 (EST)
- Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)
- Dkim-filter: OpenDKIM Filter v2.10.3 mail.efficios.com 32687B0F93
- References: <20181204192141.4684-1-mathieu.desnoyers@efficios.com> <87h8fkz6qx.fsf@oldenburg2.str.redhat.com> <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com> <87fttv9iic.fsf@oldenburg2.str.redhat.com> <394676913.486.1547493757710.JavaMail.zimbra@efficios.com> <87y37n8202.fsf@oldenburg2.str.redhat.com>
----- On Jan 14, 2019, at 2:37 PM, Florian Weimer fweimer@redhat.com wrote:
> * Mathieu Desnoyers:
>
>> ----- On Jan 14, 2019, at 10:55 AM, Florian Weimer fweimer@redhat.com wrote:
>>
>>> * Mathieu Desnoyers:
>>>
>>>> Therefore, both symbols will end up in
>>>> sysdeps/unix/sysv/linux/Versions.
>>>
>>> I'm not sure what you mean by that. The physical location in the
>>> directory tree has little effect on which shared object the symbol is
>>> placed in; that will need other changes.
>>
>> I'm currently moving the symbol definitions to csu/rseq-sym.c. On Linux,
>> its content is overridden by a new sysdeps/unix/sysv/linux/rseq-sym.c
>> which contains both __rseq_abi and __rseq_refcount symbols. On other
>> platforms, it is a stub file.
>
> You don't need a stub file if you use the “ifeq ($(subdir),csu)”
> construct.
OK
>
> The other question is whether this belongs into the csu subdirectory.
> Since TLS is not available in ld.so, the initialization would have to
> happen rather late, after relocation, but before ELF constructors are
> run.
>
> (A side effect is that the rseq area would not be usable from IFUNC
> resolvers.)
Do you have a specific directory location in mind where we should put
the built object ? e.g. "ifeq ($(subdir),posix)" or
"ifeq ($(subdir),misc)" ?
Moreover, from where should we call the rseq initialization ? I'm having
trouble with invalid system calls parameters if I place it in
LIBC_START_MAIN() just before or after the call to __pthread_initialize_minimal.
I get what appears to be invalid parameters to sys_rseq, possibly due to
stack corruption (?). I'm investigating at the moment. But if you prefer
we call the rseq init from elsewhere, please let me know.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com