Commit Graph

10 Commits

Author SHA1 Message Date
Matthew Dillon
b08440e568 Correct a bug in the last commit. The whole point of creating a 'done:'
goto target was so the cache could be freed.  So free the cache after
done: rather then before done: (!)

Submitted by:	Gavin Atkinson <gavin@ury.york.ac.uk>
2002-06-10 21:15:50 +00:00
Matthew Dillon
b603db3019 In tracking down an installation seg fault with then openoffice port
Martin Blapp determined that the elf dynamic loader was at fault.  In
particular, the loader uses alloca() to allocate a symbol cache on the
stack.  Normally this would work just fine, but if the loader is called
from a threaded program and the object being loaded is fairly large the
alloca() can blow away the thread stack and effect other nearby thread
stacks as well.  My testing showed that the symbol cache can be as large
as 250KBytes during the openoffice port build and install sequence.  Martin
was able to work around the problem by disabling the symbol cache
(cache = NULL;).  However, this solution is not adequate for commit because
it can cause an enormous cpu burden for applications which do a lot of
dynamic loading (e.g. like konqueror).

The solution is to use anonymous mmap() to temporarily allocate space to
hold the symbol cache.  In testing I found that replacing the alloca()
with mmap() has no observable degredation in performance.

It should be noted that this bug does not necessarily cause an immediate
crash but can instead result in long term corruption and instability in
applications that load modules from threads.  The bug is almost certainly
responsible for some of the instabilities found in konqueror, for example,
and possibly netscape too.

Sleuthing work by: Martin Blapp <mb@imp.ch>
X-MFC after:	Before or after the 4.6 release depending on the release engineers
2002-06-10 18:52:31 +00:00
Doug Rabson
b5393d9f78 Add ia64 support. Various adjustments were made to existing targets to
cope with a few interface changes required by the ia64. In particular,
function pointers on ia64 need special treatment in rtld.
2001-10-15 18:48:42 +00:00
John Polstra
c15e7faad5 Performance improvements for the ELF dynamic linker. These
particularly help programs which load many shared libraries with
a lot of relocations.  Large C++ programs such as are found in KDE
are a prime example.

While relocating a shared object, maintain a vector of symbols
which have already been looked up, directly indexed by symbol
number.  Typically, symbols which are referenced by a relocation
entry are referenced by many of them.  This is the same optimization
I made to the a.out dynamic linker in 1995 (rtld.c revision 1.30).

Also, compare the first character of a sought-after symbol with its
symbol table entry before calling strcmp().

On a PII/400 these changes reduce the start-up time of a typical
KDE program from 833 msec (elapsed) to 370 msec.

MFC after:	5 days
2001-05-05 23:21:05 +00:00
John Polstra
7dbe16fbee When a threads package registers locking methods with dllockinit(),
figure out which shared object(s) contain the the locking methods
and fully bind those objects as if they had been loaded with
LD_BIND_NOW=1.  The goal is to keep the locking methods from
requiring any lazy binding.  Otherwise infinite recursion occurs
in _rtld_bind.

This fixes the infinite recursion problem in the linuxthreads port.
2000-01-29 01:27:04 +00:00
John Polstra
d3980376e8 Add a new function dllockinit() for registering thread locking
functions to be used by the dynamic linker.  This can be called by
threads packages at start-up time.  I will add the call to libc_r
soon.

Also add a default locking method that is used up until dllockinit()
is called.  The default method works by blocking SIGVTALRM, SIGPROF,
and SIGALRM in critical sections.  It is based on the observation
that most user-space threads packages implement thread preemption
with one of these signals (usually SIGVTALRM).

The dynamic linker has never been reentrant, but it became less
reentrant in revision 1.34 of "src/libexec/rtld-elf/rtld.c".
Starting with that revision, multiple threads each doing lazy
binding could interfere with each other.  The usual symptom was
that a symbol was falsely reported as undefined at start-up time.
It was rare but not unseen.  This commit fixes it.
1999-12-27 04:44:04 +00:00
Peter Wemm
7f3dea244c $Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00
John Polstra
962fdc466a Fix a serious performance bug for large programs on the Alpha,
discovered by Hidetoshi Shimokawa.  Large programs need multiple
GOTs.  The lazy binding stub in the PLT can be reached from any of
these GOTs, but the dynamic linker only has enough information to
fix up the first GOT entry.  Thus calls through the other GOTs went
through the time-consuming lazy binding process on every call.

This fix rewrites the PLT entries themselves to bypass the lazy
binding.

Tested by Hidetoshi Shimokawa and Steve Price.

Reviewed by:	Doug Rabson <dfr@freebsd.org>
1999-06-25 02:53:59 +00:00
John Polstra
d5b537d01a Eliminate all machine-dependent code from the main source body and
the Makefile, and move it down into the architecture-specific
subdirectories.

Eliminate an asm() statement for the i386.

Make the dynamic linker work if it is built as an executable instead
of as a shared library.  See i386/Makefile.inc to find out how to
do it.  Note, this change is not enabled and it might never be
enabled.  But it might be useful in the future.  Building the
dynamic linker as an executable should make it start up faster,
because it won't have any relocations.  But in practice I suspect
the difference is negligible.
1999-04-09 00:28:43 +00:00
Doug Rabson
13575fc46f Add alpha support.
Submitted by: John Birrell <jb@cimlogic.com.au> (with extra hacks by me)
Obtained from: Probably NetBSD
1998-09-04 19:03:57 +00:00