Commit Graph

34 Commits

Author SHA1 Message Date
Doug Rabson
017246d02f Add support for Thread Local Storage. 2004-08-03 08:51:00 +00:00
Peter Wemm
c905e45dc0 Add initial support for compiling a special 32 bit version of
ld-elf.so.1 on 64 bit systems.  Most of this involves using alternate
paths, environment variables and diagnostic messages.

The build glue is seperate.
2004-03-21 01:21:26 +00:00
Gordon Tetlow
7b73593acd Prepend /lib to the builtin library search path in rtld. 2003-08-17 07:55:17 +00:00
Matthew N. Dodd
c5d061c17a Provide a mechanism for dumping relocation information.
Setting the LD_DUMP_REL_PRE or LD_DUMP_REL_POST environment variables
cause rtld-elf to output a table of all relocations.

This is useful for debugging.
2003-06-19 03:55:38 +00:00
Matthew N. Dodd
94040887ee Move MD function prototypes together. 2003-06-19 02:42:04 +00:00
Matthew N. Dodd
2c297acb7a Fix warnings; no parameters in function prototypes. 2003-06-19 02:39:37 +00:00
Matthew N. Dodd
da9f245470 - Add support for DT_FLAGS.
- Define various things from the most recent ELF spec.
2003-06-18 03:34:29 +00:00
Alexander Kabaev
6d5d786f80 Allow threading libraries to register their own locking
implementation in case default one provided by rtld is
not suitable.

Consolidate various identical MD lock implementation into
a single file using appropriate machine/atomic.h.

Approved by:	re (scottl)
2003-05-29 22:58:26 +00:00
Alexander Kabaev
42d206e975 Implement dlinfo() function.
Introdice RTLD_SELF special handle and properly process it within
dlsym() and dlinfo() functions.

The intention is to improve our compatibility with Solaris and
to make a Java port easier.

Partially submitted by:	phantom
2003-02-13 17:47:44 +00:00
Alexander Kabaev
d38a104b75 Remove /usr/lib/elf from a default search path.
Move xprintf to malloc.c, it is only used there. Make static.

Submitted by:	phantom
2003-02-13 17:05:10 +00:00
Peter Wemm
14a55adf36 Update rtld for the "new" ia64 ABI. In the old toolchain, the
DT_INIT and DT_FINI tags pointed to fptr records.  In 2.11.2, it points
to the actuall address of the function.  On IA64 you cannot just take
an address of a function, store it in a function pointer variable and
call it.. the function pointers point to a fptr data block that has the
target gp and address in it.  This is absolutely necessary for using
the in-tree binutils toolchain, but (unfortunately) will not work with
old shared libraries.  Save your old ld-elf.so.1 if you want to use
old ones still.  Do not mix-and-match.

This is a no-op change for i386 and alpha.

Reviewed by:	dfr
2001-10-29 10:10:10 +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
David E. O'Brien
5e6220d9d0 * include/elf.h has been repo copied to include/elf-hints.h, and it no
longer includes machine/elf.h.
* consumers of elf.h now use the minimalist elf header possible.

This change is motivated by Binutils 2.11.0 and too much clashing over
our base elf headers and the Binutils elf headers.
2001-05-02 23:56:21 +00:00
John Polstra
185db83c04 Add support for dlsym(RTLD_DEFAULT, ...). 2000-09-19 04:27:16 +00:00
John Polstra
44a028c369 Revamp the code that calls shared libraries' init and fini functions.
Formerly the init functions were called in the opposite of the
order in which libraries were loaded, and libraries were loaded
according to a breadth-first traversal of the dependency graph.
That ordering came from SVR4.0, and it was easy to implement but
not always sensible.

Now we do a depth-first walk over the dependency graph and call
the init functions in an order such that each shared object's needed
objects are initialized before the shared object itself.  At the
same time we build a list of finalization (fini) functions in the
opposite order, to guarantee correct C++ destructor ordering whenever
possible.  (It may not be possible if dlopen and dlclose are used
in strange ways, but we come as close as one can come.)

The need for this renovation has become apparent as more programs
have started using multithreading.  The multithreaded C library
libc_r requires initialization, whereas the standard libc does not.
Since virtually every other object depends on the C library, it is
important that it get initialized first.
2000-07-26 04:24:40 +00:00
John Polstra
630df077ab Solve the dynamic linker's problems with multithreaded programs once
and for all (I hope).  Packages such as wine, JDK, and linuxthreads
should no longer have any problems with re-entering the dynamic
linker.

This commit replaces the locking used in the dynamic linker with a
new spinlock-based reader/writer lock implementation.  Brian
Fundakowski Feldman <green> argued for this from the very beginning,
but it took me a long time to come around to his point of view.
Spinlocks are the only kinds of locks that work with all thread
packages.  But on uniprocessor systems they can be inefficient,
because while a contender for the lock is spinning the holder of the
lock cannot make any progress toward releasing it.  To alleviate
this disadvantage I have borrowed a trick from Sleepycat's Berkeley
DB implementation.  When spinning for a lock, the requester does a
nanosleep() call for 1 usec. each time around the loop.  This will
generally yield the CPU to other threads, allowing the lock holder
to finish its business and release the lock.  I chose 1 usec. as the
minimum sleep which would with reasonable certainty not be rounded
down to 0.

The formerly machine-independent file "lockdflt.c" has been moved
into the architecture-specific subdirectories by repository copy.
It now contains the machine-dependent spinlocking code.  For the
spinlocks I used the very nifty "simple, non-scalable reader-preference
lock" which I found at

  <http://www.cs.rochester.edu/u/scott/synchronization/pseudocode/rw.html>

on all CPUs except the 80386 (the specific CPU model, not the
architecture).  The 80386 CPU doesn't support the necessary "cmpxchg"
instruction, so on that CPU a simple exclusive test-and-set lock
is used instead.  80386 CPUs are detected at initialization time by
trying to execute "cmpxchg" and catching the resulting SIGILL
signal.

To reduce contention for the locks, I have revamped a couple of
key data structures, permitting all common operations to be done
under non-exclusive (reader) locking.  The only operations that
require exclusive locking now are the rare intrusive operations
such as dlopen() and dlclose().

The dllockinit() interface is now deprecated.  It still exists,
but only as a do-nothing stub.  I plan to remove it as soon as is
reasonably possible.  (From the very beginning it was clearly
labeled as experimental and subject to change.)  As far as I know,
only the linuxthreads port uses dllockinit().  This interface turned
out to have several problems.  As one example, when the dynamic
linker called a client-supplied locking function, that function
sometimes needed lazy binding, causing re-entry into the dynamic
linker and a big looping mess.  And in any case, it turned out to be
too burdensome to require threads packages to register themselves
with the dynamic linker.
2000-07-08 04:10:38 +00:00
Jake Burkholder
e39756439c Back out the previous change to the queue(3) interface.
It was not discussed and should probably not happen.

Requested by:		msmith and others
2000-05-26 02:09:24 +00:00
Jake Burkholder
740a1973a6 Change the way that the queue(3) structures are declared; don't assume that
the type argument to *_HEAD and *_ENTRY is a struct.

Suggested by:	phk
Reviewed by:	phk
Approved by:	mdodd
2000-05-23 20:41:01 +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
9bfb1dfc29 Revamp the mechanism for enumerating and calling shared objects'
init and fini functions.  Now the code is very careful to hold no
locks when calling these functions.  Thus the dynamic linker cannot
be re-entered with a lock already held.

Remove the tolerance for recursive locking that I added in revision
1.2 of dllockinit.c.  Recursive locking shouldn't happen any more.

Mozilla and JDK users: I'd appreciate confirmation that things still
work right (or at least the same) with these changes.
2000-01-09 21:13:48 +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
John Polstra
825316056a Make jdk-1.1.8 work again. It turns out that some code inside
libjava peeks into the dynamic linker's private Obj_Entry structures.
My recent changes introduced some new members near the front of
the structures, causing libjava to get the wrong fields.  This commit
moves the new members toward the end of the structure so that the
layout of the portion that is relevant to JDK remains the same as
before.

I will work with the JDK porting team to see if we can come up with
a less fragile way for them to do what they need to do.  I understand
the current approach was necessary in order to work around some
limitations of the dynamic linker.  Maybe it's not necessary any
more.
1999-09-05 21:12:53 +00:00
John Polstra
a607e5d7f8 Get the actual pathname of the dynamic linker from the executable's
PT_INTERP program header entry, to ensure that gdb always finds
the right dynamic linker.

Use obj->relocbase to simplify a few calculations where appropriate.
1999-08-30 01:54:13 +00:00
John Polstra
7360ae0f2a When checking to see if a shared object is already loaded, look for
a device/inode match if no pathname match is found.
1999-08-30 01:50:41 +00:00
John Polstra
926ea445fe Revamp the symbol lookup algorithm to cope better with objects
loaded separately by dlopen that have global symbols with identical
names.  Viewing each dlopened object as a DAG which is linked by its
DT_NEEDED entries in the dynamic table, the search order is as
follows:

  * If the referencing object was linked with -Bsymbolic, search it
    internally.
  * Search all dlopened DAGs containing the referencing object.
  * Search all objects loaded at program start up.
  * Search all objects which were dlopened() using the RTLD_GLOBAL
    flag (which is now supported too).

The search terminates as soon as a strong definition is found.
Lacking that, the first weak definition is used.

These rules match those of Solaris, as best I could determine them
from its vague manual pages and the results of experiments I performed.

PR:		misc/12438
1999-08-30 01:48:19 +00:00
Peter Wemm
7f3dea244c $Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00
John Polstra
bfb1ef6058 Change many asserts into normal errors. They were all for conditions
caused by invalid shared objects rather than by internal errors.

Enable format string mismatch checking for _rtld_error().
1999-07-18 00:02:19 +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
John Polstra
63fac2b9ef Suppress duplicate entries in ldd output. 1998-09-02 02:51:12 +00:00
John Birrell
1eab1be09e Update this header to use the revamped elf headers which select Elf32
or Elf64 based on the inclusion of the machine dependent header.

I've left the addition of the extra fields to handle the relocation
structures with addend for a separate commit after jdp has had a chance
to review what I've done. The current change is needed to compile
csu/alpha/crt1.c
1998-08-21 03:29:40 +00:00
Doug Rabson
2001f720ce Add GDB support. The method and some of the code came from NetBSD's elf
runtime linker.
1998-04-30 07:48:02 +00:00
John Polstra
3124c3e093 Import the ELF dynamic linker. This is the ElfKit version with
quite a few enhancements and bug fixes.  There are still some known
deficiencies, but it should be adequate to get us started with ELF.

Submitted by:	John Polstra <jdp@polstra.com>
1998-03-07 19:24:35 +00:00