emacs a.out file, self-generated by emacs's "unexec" function in
"unexsunos4.c", is invalid. In particular, its "_end" symbol has
the wrong value. The dynamic linker was using the value of that
symbol to initialize its sbrk break level.
The workaround is to peek at the executable's a.out header in
memory, and calculate what "_end" should be based on the segment
sizes.
I will work out a fix for emacs and send it to the FSF. This
dynamic linker workaround is still worthwhile, if only to avoid
forcing all emacs users to build a new version.
Note: xemacs gives a bogus warning at startup, for related reasons.
The warning is harmless and can safely be ignored. I will send a
patch to the xemacs maintainers to get rid of it, and meanwhile
add a patch file to our port.
things so that it uses the same malloc as is used by the program
being executed. This has several advantages, the big one being
that you can now debug core dumps from dynamically linked programs
and get useful information out of them. Until now, that didn't
work. The internal malloc package placed the tables describing
the loaded shared libraries in a mapped region of high memory that
was not written to core files. Thus the debugger had no way of
determining what was loaded where in memory. Now that the dynamic
linker uses the application's malloc package (normally, but not
necessarily, the system malloc), its tables end up in the regular
heap area where they will be included in core dumps. The debugger
now works very well indeed, thank you very much.
Also ...
Bring the program a little closer to conformance with style(9).
There is still a long way to go.
Add minimal const correctness changes to get rid of compiler warnings
caused by the recent const changes in <dlfcn.h> and <link.h>.
Improve performance by eliminating redundant calculations of symbols'
hash values.
plain 0 should be used. This happens to work because we #define
NULL to 0, but is stylistically wrong and can cause problems
for people trying to port bits of code to other environments.
PR: 2752
Submitted by: Arne Henrik Juul <arnej@imf.unit.no>
Add a -Bforcedynamic option which generates a dynamic object even
if no shared libraries were given in the link.
Make RRS in text section warnings conditional on "-assert pure-text"
so that I can link non-PIC kernel modules without tons of link
errors. Changes to bsd.lib.mk to follow.
Fix a couple of bugs exposed by the fact that the kernel is not
linked at zero.
Reviewed by: jdp
ld-specific flags. LDFLAGS is really for ld-related flags for cc,
not for ld, and some flags, e.g., -Bshareable, mean completely
different things to cc and ld. Having the wrong things in LDFLAGS
also broke the standard ${PROG} target. This was kludged around
by using a special rule that depended on LDFLAGS being bogus.
Fixing `make depend' broke the special rule but fixed the standard
rule (except in the DESTDIR case, which was handled more strictly
here than elsewhere).
If it is set to a nonempty string, then simply skip any missing
shared libraries. This came up in a discussion long ago as a
potentially useful feature at sysinstall time. For example, an
X11 utility could be used without the X libraries being present,
provided the utility had a mode in which no X functions were actually
called.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
nonempty string, then function calls are relocated at program start-up
rather than lazily. This variable is standard on Sun and SVR4 systems.
The dlopen() function now supports both lazy and immediate binding, as
determined by its "mode" argument, which can be either 1 (RTLD_LAZY) or
2 (RTLD_NOW). I will add defines of these symbols to <dlfcn.h> as soon
as I've done a little more checking to make sure they won't cause
collisions or bootstrapping problems that would break "make world".
The "LD_*" environment variables which alter dynamic linker behavior are
now treated as unset if they are set to the empty string. This agrees
with the standard SVR4 conventions for the dynamic linker.
Add a work-around for programs compiled with certain buggy versions of
crt0.o. The buggy versions failed to set the "crt_ldso" member of the
interface structure. This caused certain error messages from the
dynamic linker to begin with "(null)" instead of the pathname of the
dynamic linker.
nonempty string, then function calls are relocated at program start-up
rather than lazily. This variable is standard on Sun and SVR4 systems.
The dlopen() function now supports both lazy and immediate binding, as
determined by its "mode" argument, which can be either 1 (RTLD_LAZY) or
2 (RTLD_NOW). I will add defines of these symbols to <dlfcn.h> as soon
as I've done a little more checking to make sure they won't cause
collisions or bootstrapping problems that would break "make world".
the main program, report them directly from the dynamic linker and die
there, rather than returning an error message to crt0.o. This enables
the printing of error messages even for old executables, whose version
of crt0.o is not able to print them.
This fix closes PR bin/1869.
The code in crt0.o for printing error messages from the dynamic linker
is no longer used, because of this change. But it must remain, for
backward compatibility with older dynamic linkers.
opened. After that, the directories are already present, and there is
no point in adding them again. This doesn't fix any bugs; it's just for
efficiency.
since rt_readenv() already takes care of not setting unsafe variables.
This was part of the changes I submitted to Peter and John during the
review which must have gotten missed.
how I managed to get this out of sync, but I did. I guess that's what I
get for directly committing from different machines that I was testing on.
Pointed out by: Paul Traina <pst@freebsd.org>
configurable fallback search paths, as well as new crt interface version.
Also:
- even faster getenv(), get all environment variable settings in a single
pass.
- ldd printf-like format specifications
- minor code cleanups, one vsprintf -> vsnprintf (harmless)
The library search sequence is a little more complete now. Before,
it'd search $LD_LIBRARY_PATH (by opendir/readdir/closedir), then read
the hints file, then read /usr/lib (again by scanning thr directory). It
would then fail if there was no "found" library.
Now, it does LD_LIBRARY_PATH and the hints file the same, but then uses
a longer fallback path. The -R path is fetched from the executable if
specified at build time, the ldconfig path is appended, and /usr/lib is
appended to that. Duplicates are suppressed. This means that simply
placing a new library in /usr/local/lib will work (the same as it did in
/usr/lib) without needing ldconfig -m. It will find it quicker if the
ldconfig is run though.
Similar changes have been made to the NetBSD ld.so, but ours is rather
different now due to John Polstra's speedups and fixes from a while back.
The ldd printf-like format support came direct from NetBSD.
Reviewed by: nate, jdp
with the -R option and store the path in the dynamic header when specified.
The $LD_RUN_PATH environment variable is not checked yet.
While here, split up the code a bit more to enable more selective replacing
of GPL'ed components that are linked with ld.so with others.
Obtained from: NetBSD (mostly, the breakup is my fault)
as atomically as possible.
(Immutable targets can't be renamed without opening a window when
neither the source nor the target is immutable. Perhaps there
should be a rename_immutable syscall to do this if unsetting the
immutable flags would work.)
been loaded, look for a match by device and inode number if the
traditional pathname comparisons don't find a match. This detects
the case in which a library is requested using two different names
which are really links to the same file, and avoids loading it
twice.
Requested by: peter@freebsd.org
Reviewed by: peter@freebsd.org
descriptions of LD_NO_INTERN_SEARCH and LD_NOSTD_PATH from the manual
page, since they are not supported.
Submitted by: Doug Ambrisko <ambrisko@ambrisko.roble.com>
It addresses a number of problems that were present in earlier
versions.
The calls to the "init" and "fini" functions of shared libraries
have been reordered, so that they are called in a strictly nested
fashion, as is required for C++ constructors and destructors. In
addition, the "init" functions are called in better order relative
to each other. That makes the system more tolerant of C++ programs
which depend on a library's being initialized before its clients.
The dynamic linker is now more tolerant of shared libraries in
which dependencies on other shared libraries are incompletely
recorded.
Cleanup in the event of errors has been improved throughout the
dynamic linker. A number of memory leaks were eliminated.
The warning message for a shared library whose minor version number
is too old has been clarified.
The code dealing with the "ld.so.hints" file has been cleaned up.
A bug that caused the hints file to be unmapped incompletely has
been fixed. A different bug that could potentially cause the hints
file to be mapped on top of a loaded object has been fixed.
The code that searches for shared libraries has been cleaned up.
The searching is now more compatible with that done by SunOS and
SVR4. Also, some unnecessary and useless searches of both the
hints file and library directories have been eliminated.
Reviewed by: nate@freebsd.org
vector. Now it is called the "symbol caching" vector. This was made
possible and unconfusing by other changes that allowed me to localize
everything having to do with the caching vector in the function
reloc_map().
Switched to alloca() for allocating the caching vector, and eliminated
the special mmap-based allocation routines. Although this was motivated
by performance reasons, it led to significant simplification of the
code, and made it possible to confine the symbol caching code to the
single function reloc_map().
Got rid of the unnecessary and inefficient division loop at the
beginning of rtld().
Reduced the number of calls to getenv("LD_LIBRARY_PATH") to just 1, on
suggestion from <davidg@root.com>.
Added breaks out of the relocation loops when the relocation address is
found to be 0. A relocation address of 0 is caused by an unused
relocation entry. Unused relocation entries are caused by linking a
shared object with the "-Bsymbolic" switch. The runtime linker itself
is linked that way, and the last 40% of its relocation entries are
unused. Thus, breaking out of the loop on the first such entry is a
performance win when ld.so relocates itself. As a side benefit, it
permits removing a test from md_relocate_simple() in
../i386/md-static-funcs.c.
Unused relocation entries in other shared objects (linked with
"-Bsymbolic") caused even bigger problems in previous versions of the
runtime linker. The runtime linker interpreted the unused entries as if
they were valid. That caused it to perform repeated relocations of the
first byte of the shared object. In order to do that, it had to remap
the text segment writable. Breaking out of the loop on the first unused
relocation entry solves that.
Submitted by: John Polstra <jdp@polstra.com>
Implemented symbol memorizing to reduce the number of calls to lookup(),
making relocation go faster. While relocating a given shared object,
the dynamic linker maintains a memorizing vector that is directly
indexed by the symbol number in the relocation entry. The first time a
given symbol is looked up, the memorizing vector is filled in with a
pointer to the symbol table entry, and a pointer to the so_map of the
shared object in which the symbol was defined. On subsequent uses of
the same symbol, that information is retrieved directly from the
memorizing vector, without calling lookup() again.
A symbol that is referenced in a relocation entry is typically
referenced in many relocation entries, so this memorizing reduces the
number of calls to lookup() dramatically. The overall improvement in
the speed of dynamic linking is also dramatic -- as much as a factor of
three for programs that use many shared libaries.
Submitted by: jdp@polstra.com "John Polstra"
shared library. Formerly, the message looked like this:
ld.so: run: libjdp1.so.1.0: Undefined error: 0
The new message looks like this:
ld.so: run: Can't find shared library "libjdp1.so.1.0"
(Where "run" is the name of the program being executed.)
Submitted by: jdp@polstra.com (John Polstra)
symbols.
An easy example to see this is to develop an X program which links
against Xt, but doesn't add -lX11 to the link line. It will link fine,
but cause run-time errors by ld.so because of missing symbols used by Xt
defined in X11. This patch makes the errors more readable.
Submitted by: jdp@polstra.com (John Polstra)
