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[Bug libc/16291] New: feature request: provide simpler ways to compute stack and tls boundaries
- From: "konstantin.s.serebryany at gmail dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Wed, 04 Dec 2013 04:49:50 +0000
- Subject: [Bug libc/16291] New: feature request: provide simpler ways to compute stack and tls boundaries
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=16291
Bug ID: 16291
Summary: feature request: provide simpler ways to compute stack
and tls boundaries
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: libc
Assignee: unassigned at sourceware dot org
Reporter: konstantin.s.serebryany at gmail dot com
CC: drepper.fsp at gmail dot com
This is both a feature request and a request for a suggestion.
We are developing dynamic testing tools like AddressSanitizer and
ThreadSanitizer
which are now part of both LLVM and GCC distributions.
The tools have a run-time library that needs to compute thread's stack and
tls boundaries. Right now it is done with a series of ugly hacks.
For non-main threads we get the stack boundaries by querying
pthread_getattr_np and pthread_attr_getstack. This works,
but is problematic because pthread_getattr_np calls malloc and we intercept
malloc.
For the main thread we get the stack boundaries by querying
getrlimit, /proc/self/maps, and an address of a local variable because at the
point when we need the info libpthread might not have initialized itself.
Getting TLS boundaries is even more involved.
Today we use the glibc's private symbol _dl_get_tls_static_info
and then subtract a magic constant (size of the glibc's thread descriptor).
Most of the code is here:
http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux_libcdep.cc?revision=195441
(GetThreadStackTopAndBottom and InitTlsSize)
This works for us on a system we are testing (Ubuntu 12.04),
but this is very fragile and is often broken on older Linux distros.
Is it possible to compute the stack and tls boundaries more reliably today?
If not, would it be possible to add some new functions to do that?
For every thread (including the main one) we need to know its stack and tls
boundaries and the functions that compute it for us should not call malloc
or any other public library functions. For the main thread, these functions
should
work reliably very early (in pre_init functions)
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