Commit Graph

99 Commits

Author SHA1 Message Date
Ruslan Ermilov
c4d9468ea0 mdoc(7) police:
Avoid using parenthesis enclosure macros (.Pq and .Po/.Pc) with plain text.
Not only this slows down the mdoc(7) processing significantly, but it also
has an undesired (in this case) effect of disabling hyphenation within the
entire enclosed block.
2001-08-07 15:48:51 +00:00
Sheldon Hearn
e1b4d8d074 Use STD{ERR,IN,OUT}_FILENO instead of their numeric values. The
definitions are more readable, and it's possible that they're
more portable to pathalogical platforms.

Submitted by:   David Hill <david@phobia.ms>
2001-07-26 11:02:39 +00:00
Ruslan Ermilov
0efe23d669 mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 10:49:54 +00:00
Dima Dorfman
70d51341bf mdoc(7) police: remove extraneous .Pp before and/or after .Sh. 2001-07-09 09:54:33 +00:00
Ruslan Ermilov
5521ff5a4d mdoc(7) police: sort SEE ALSO xrefs (sort -b -f +2 -3 +1 -2). 2001-07-06 16:46:48 +00:00
Ruslan Ermilov
4cf39050cc Use new backup feature of install(1). 2001-05-28 16:58:35 +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
Ruslan Ermilov
e5b5c66bca - Backout botched attempt to intoduce MANSECT feature.
- MAN[1-9] -> MAN.
2001-03-26 14:22:12 +00:00
Ruslan Ermilov
896eb7d10c Prepare for mdoc(7)NG. 2001-01-16 09:15:57 +00:00
John Polstra
27e2c03506 Fix a bug in which a program called dlclose from a destructor and
got an assert failure in the dynamic linker.
2001-01-05 04:36:17 +00:00
Ruslan Ermilov
58eaff2332 Prepare for mdoc(7)NG. 2000-12-20 13:26:01 +00:00
David E. O'Brien
1a37aa566b Add `_PATH_DEVZERO'.
Use _PATH_* where where possible.
2000-12-09 09:35:55 +00:00
John Polstra
c1ff193db4 Remove the superfluous call to _rtld_error() in symlook_default().
The function's callers generate the error message when appropriate.

This eliminates the message ``Undefined symbol "__register_frame_info"''
which was bogusly returned by dlerror() in some cases.
2000-11-07 22:41:53 +00:00
John Polstra
185db83c04 Add support for dlsym(RTLD_DEFAULT, ...). 2000-09-19 04:27:16 +00:00
John W. De Boskey
bde08d0072 Pass two pointer parameters to the r_debug_state() hook
function, thus allowing a debugger or other trace tool
to easily grab the addresses of the needed structures
off the stack.

This change is transparent to gdb, which locates the
link_map list and transfers it to debugger memory
for comparison purposes.

A sample program will be committed showing how this can
be used.

Reviewed by:    John Polstra <jdp@FreeBSD.org>
2000-08-26 05:13:29 +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
Brian Feldman
119fc1a3ce We shouldn't use cp to save the old ld-elf.so.1. Use the sanctioned tool
${INSTALL} with -C -p instead.
2000-07-20 08:00:02 +00:00
John Polstra
cf98e66403 Fix a bug which could cause programs with user threads packages to
lock against themselves, causing infinite spinning.  Brian Feldman
found this problem when testing with Mozilla and supplied the fix,
which I have revised slightly.

Here is the failure scenario.  A thread calls dlopen() and acquires
the writer lock.  While the thread still holds the lock, a signal
is delivered and caught.  The signal handler tries to call a function
which hasn't been bound yet.  It thus enters the dynamic linker
and tries to acquire the reader lock.  Since the writer lock is
already held, it will spin forever in the signal handler.  The
thread holding the lock won't be able to progress and release the
lock.

The solution is to block almost all signals while holding the
exclusive lock.

A similar problem could conceivably occur in the opposite order.
Namely, a thread is holding the reader lock and then a signal
handler calls dlopen() or dlclose() and spins waiting for the writer
lock.  We deal with this administratively by proclaiming that signal
handlers aren't allowed to call dlopen() or dlclose().  Actually
we don't have to proclaim a thing, since signal handlers aren't
allowed to call any system functions except those which are explicitly
permitted.

Submitted by:	Brian Fundakowski Feldman <green>
2000-07-17 17:18:13 +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
John Polstra
517191eede When installing the dynamic linker, save the previous version in
"ld-elf.so.1.old".  The dynamic linker is a critical component of
the system, and it is difficult to recover if it is damaged and
there isn't a working backup available.  For instance, parts of
the toolchain such as the assembler are dynamically linked, making
it impossible to build a new dynamic linker if the installed one
doesn't work.
2000-07-08 03:27:54 +00:00
Sheldon Hearn
cbe10916b3 Only punctuation is an allowed argument type for open-close macros
such as Po/Pc, as explained by phantom.

Reported by:	billf
2000-06-30 06:30:53 +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
a0f2601e13 Eliminate unaligned accesses that occurred when relocating the
DWARF2 exception tables emitted by the compiler for C++ sources.
These tables are tightly packed, and they contain some relocated
addresses which are not well-aligned.
2000-05-22 16:31:18 +00:00
Sheldon Hearn
35add0e9a7 Cross-reference ldd(1) in rtld(1) and vice versa. 2000-03-28 09:01:04 +00:00
Bruce Evans
9d08570309 Fixed missing DPADDs.
Fixed some style bugs (some usual ones for LDADD, and misformatting of
$FreeBSD$).
2000-03-27 16:11:27 +00:00
John Polstra
ea5cc7f114 Add a manual page for the ELF dynamic linker. I initially created
rtld.1 by means of a repository copy from "src/libexec/rtld-aout/rtld.1".
Then I edited it to make it (more) accurate for the ELF dynamic
linker.
2000-01-29 03:16:54 +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
5bc2f0f789 Block almost all signals in the default locking method instead of
just a few of them.  This looks like it solves the recent

  ld-elf.so.1: assert failed: /usr/src/libexec/rtld-elf/lockdflt.c:55

failures seen by some applications such as JDK.
2000-01-25 01:32:56 +00:00
John Polstra
924d965ba0 Allow files in LD_PRELOAD to be separated by white space, like Solaris
and Linux.
2000-01-22 22:20:05 +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
3600eb76c6 Work around an assert failure in the dynamic linker's default thread
locking functions.  If an application loads a shared object with
dlopen() and the shared object has an init function which requires
lazy binding, then _rtld_bind is called when the thread is already
inside the dynamic linker.  This leads to a recursive acquisition
of the lock, which I was not expecting -- hence the assert failure.

This work-around makes the default locking functions handle recursive
locking.  It is NOT the correct fix -- that should be implemented
at the generic locking level rather than in the default locking
functions.  I will implement the correct fix in a future commit.

Since the dllockinit() interface will likely need to change, warn
about that in both the man page and the header file.
1999-12-28 04:38:17 +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
df618d033c In revision 1.21 I changed the search order for shared libraries,
but I forgot to make the corresponding fix to the comment.  Rectify
that.

Submitted by:	Tony Finch <fanf@demon.net>
1999-11-19 04:45:07 +00:00
Alexey Zelkin
8bd2d9a0e6 .Nm += "rtld"
apropos(1) now knows about rtld(1) manpage.
1999-09-28 05:35:59 +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
0edd3ca778 Enable -Wformat checking for debug_printf(). 1999-09-04 20:36:27 +00:00
John Polstra
ed5e1b5537 Change the warning about unrecognized entries in the dynamic table
to a debug message which is disabled in production builds of the
dynamic linker.  The condition warned about is normally harmless.

PR:		bin/12849
1999-09-04 20:14:48 +00:00
John Polstra
476015a33b When looking up symbols, search the objects loaded at program start
up first -- before the dlopened DAGs containing the referencing
object.

This makes dynamically loaded perl modules work properly again.
1999-09-04 04:00:09 +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
John Polstra
7326e0b620 When honoring -Bsymbolic, still keep searching if only a weak
definition was found in the referencing object.
1999-08-30 01:25:38 +00:00
John Polstra
6bd9374580 Simplify the logic in find_symdef(). 1999-08-30 01:24:08 +00:00
Peter Wemm
7f3dea244c $Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00
John Polstra
41f83b07a8 Add a NULL pointer check whose absence could cause segmentation
violations in certain obscure cases involving failed dlopens.  Many
thanks to Archie Cobbs for providing me with a good test case.

Eliminate a block that existed only to localize a declaration.
1999-08-20 22:33:44 +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
cb435fa919 Change the symbol used to find the end of an object's address space
from "end" to "_end".  The former does not exist in most shared
libraries.  This fixes problems in dladdr() and dlsym(RTLD_NEXT, ...).
1999-07-14 04:09:11 +00:00
Doug Rabson
e85422ad1d Add code to 'handle' R_ALPHA_NONE relocations by ignoring them. 1999-07-12 07:54:45 +00:00