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2013-07-22disable legacy init/fini processing on ARMRich Felker-0/+4
since the old, poorly-thought-out musl approach to init/fini arrays on ARM (when it was the only arch that needed them) was to put the code in crti/crtn and have the legacy _init/_fini code run the arrays, adding proper init/fini array support caused the arrays to get processed twice on ARM. I'm not sure skipping legacy init/fini processing is the best solution to the problem, but it works, and it shouldn't break anything since the legacy init/fini system was never used for ARM EABI.
2013-07-21add support for init/fini array in main program, and greatly simplifyRich Felker-8/+6
modern (4.7.x and later) gcc uses init/fini arrays, rather than the legacy _init/_fini function pasting and crtbegin/crtend ctors/dtors system, on most or all archs. some archs had already switched a long time ago. without following this change, global ctors/dtors will cease to work under musl when building with new gcc versions. the most surprising part of this patch is that it actually reduces the size of the init code, for both static and shared libc. this is achieved by (1) unifying the handling main program and shared libraries in the dynamic linker, and (2) eliminating the glibc-inspired rube goldberg machine for passing around init and fini function pointers. to clarify, some background: the function signature for __libc_start_main was based on glibc, as part of the original goal of being able to run some glibc-linked binaries. it worked by having the crt1 code, which is linked into every application, static or dynamic, obtain and pass pointers to the init and fini functions, which __libc_start_main is then responsible for using and recording for later use, as necessary. however, in neither the static-linked nor dynamic-linked case do we actually need crt1.o's help. with dynamic linking, all the pointers are available in the _DYNAMIC block. with static linking, it's safe to simply access the _init/_fini and __init_array_start, etc. symbols directly. obviously changing the __libc_start_main function signature in an incompatible way would break both old musl-linked programs and glibc-linked programs, so let's not do that. instead, the function can just ignore the information it doesn't need. new archs need not even provide the useless args in their versions of crt1.o. existing archs should continue to provide it as long as there is an interest in having newly-linked applications be able to run on old versions of musl; at some point in the future, this support can be removed.
2013-07-21fix order of fini_array execution for shared libsRich Felker-2/+2
2013-07-20add support for init_array/fini_array ctors/dtors to dynamic linkerRich Felker-2/+13
2013-07-18make the dynamic linker find its path file relative to its own locationRich Felker-1/+20
prior to this change, using a non-default syslibdir was impractical on systems where the ordinary library paths contain musl-incompatible library files. the file containing search paths was always taken from /etc, which would either correspond to a system-wide musl installation, or fail to exist at all, resulting in searching of the default library path. the new search strategy is safe even for suid programs because the pathname used comes from the PT_INTERP header of the program being run, rather than any external input. as part of this change, I have also begun differentiating the names of arch variants that differ by endianness or floating point calling convention. the corresponding changes in the build system and and gcc wrapper script (to use an alternate dynamic linker name) for these configurations have not yet been made.
2013-07-10fix invalid library phdr pointers passed to callback from dl_iterate_phdrRich Felker-9/+16
map_library was saving pointers to an automatic-storage buffer rather than pointers into the mapping. this should be a fairly simple fix, but the patch here is slightly complicated by two issues: 1. supporting gratuitously obfuscated ELF files where the program headers are not right at the beginning of the file. 2. cleaning up the map_library function so that data isn't clobbered by the time we need it.
2013-06-29implement minimal dlinfo functionRich Felker-0/+20
2013-06-29fix missing synchronization in calls from dynamic linker to global ctorsRich Felker-0/+4
this change is needed to correctly handle the case where a constructor creates a new thread which calls dlopen. previously, the lock was not held in this case. the reason for the complex logic to avoid locking whenever possible is that, since the mutex is recursive, it will need to inspect the thread pointer to get the current thread's tid, and this requires initializing the thread pointer. we do not want non-multi-threaded programs to attempt to access the thread pointer unnecessarily; doing so could make them crash on ancient kernels that don't support threads but which may otherwise be capable of running the program.
2013-06-26remove useless conditional before free from dynamic linker path codeRich Felker-1/+1
2013-06-26fix dynamic linker handling of empty path file or error reading path fileRich Felker-4/+3
previously, the path string was being used despite being invalid. with this change, empty path file or error reading the path file is treated as an empty path. this is preferable to falling back to a default path, so that attacks to prevent reading of the path file could not result in loading incorrect and possibly dangerous (outdated or mismatching ABI) libraries from. the code to strip the final newline has also been removed; now that newline is accepted as a delimiter, it's harmless to leave it in place.
2013-06-25make newline-delimited dynamic linker path file actually workRich Felker-1/+1
apparently the original commit was never tested properly, since getline was only ever reading one line. the intent was to read the entire file, so use getdelim with the null byte as delimiter as a cheap way to read a whole file into memory.
2013-06-03ensure that thread dtv pointer is never null to optimize __tls_get_addrRich Felker-4/+4
2013-04-20make dynamic linker accept : or \n as path separatorRich Felker-8/+8
this allows /etc/ld-musl-$(ARCH).path to contain one path per line, which is much more convenient for users than the :-delimited format, which was a source of repeated and unnecessary confusion. for simplicity, \n is also accepted in environment variables, though it should probably not be used there. at the same time, issues with overly long paths invoking UB or getting truncated have been fixed. such issues should not have arisen with the environment (which is size-limited) but could have been generated by a path file larger than 2**31 bytes in length.
2013-02-02fix uninitialized map_len being used in munmap failure paths in load_libraryRich Felker-3/+2
this bug seems to have been introduced when the map_library signatures was changed to return the mapping in a temp dso structure instead of into separate variables.
2013-01-23add support for RTLD_NOLOAD to dlopenRich Felker-3/+7
based on patch by Pierre Carrier <pierre@gcarrier.fr> that just added the flag constant, but with minimal additional code so that it actually works as documented. this is a nonstandard option but some major software (reportedly, Firefox) uses it and it was easy to add anyway.
2013-01-23fix regression in dlsym: rejection of special RTLD_* handles as invalidRich Felker-1/+2
2013-01-16fix warning building dynlink.c stub for static libcRich Felker-2/+2
struct dso was not defined in this case, and it's not needed in the code that was using it anyway; void pointers work just as well.
2013-01-16fix bug in dladdr that prevented resolving addresses in the PLTRich Felker-1/+1
2013-01-10check for invalid handles in dlsym/dlcloseRich Felker-1/+17
this is wasteful and useless from a standpoint of sane programs, but it is required by the standard, and the current requirements were upheld with the closure of Austin Group issue #639: http://austingroupbugs.net/view.php?id=639
2012-12-15fix breakage in ldd (failure to print library load address)Rich Felker-2/+2
2012-11-30fix ordering of shared library ctors with respect to libc initRich Felker-3/+6
previously, shared library constructors were being called before important internal things like the environment (extern char **environ) and hwcap flags (needed for sjlj to work right with float on arm) were initialized in __libc_start_main. rather than trying to have to dynamic linker make sure this stuff all gets initialized right, I've opted to just defer calling shared library constructors until after the main program's entry point is reached. this also fixes the order of ctors to be the exact reverse of dtors, which is a desirable property and possibly even mandated by some languages. the main practical effect of this change is that shared libraries calling getenv from ctors will no longer fail.
2012-11-25eliminate gdb complaints about missing linux-gate.so.1Rich Felker-1/+2
actually, the hard-coded name should be eliminated too, and replaced by a search for the soname in the headers, but that can be done separately later.
2012-11-17fix typo in dynamic linker path file loading codeRich Felker-1/+1
fortunately the memory corruption could not hurt anything, but it prevented clearing the final newline and thus prevented the last path element from working.
2012-11-17arg-skipping code for powerpc dynamic linkerRich Felker-0/+8
this allows using the dynamic linker as a command to load programs.
2012-11-16dynamic linking support for powerpcRich Felker-17/+16
incomplete but at least partly working. requires all files to be compiled in the new "secure" plt model, not the old one that put plt code in the data segment. TLS is untested but may work. invoking the dynamic linker explicitly to load a program does not yet handle argv correctly.
2012-11-14fix indention with spaces in powerpc asmRich Felker-27/+26
2012-11-14Merge remote-tracking branch 'ppc-port/ppc-squashed'Rich Felker-0/+31
2012-11-13PPC port cleaned up, static linking works well now.rofl0r-24/+24
2012-11-13import preliminary ppc work by rdp.Richard Pennington-0/+31
2012-11-09support ldso path files without final newlineRich Felker-2/+5
2012-11-08change ldso path file logic to replace rather than add to search pathRich Felker-2/+2
this change was originally intended just to avoid repeated attempts to open a nonexistant /etc/ls-musl-$(ARCH).path file, but I realized it also prevents the default paths from being searched when such a path file exists. despite the potential to break existing usage, I believe the new behavior is the right behavior, and it's better to fix it sooner rather than later. with the old behavior, it was impossible to inhibit search of default paths which might contain musl-incompatible libs (or even libs from a different cpu arch, on multi-arch machines).
2012-11-08fix dlsym asm for mipsRich Felker-1/+2
saving the return address from the delay slot is not valid -- by the time the instruction executes, the return address has already been replaced.
2012-11-01remove one unnecessary static var from dynamic linkerRich Felker-2/+2
2012-11-01fix more unused variable warningsRich Felker-3/+2
some of these were coming from stdio functions locking files without unlocking them. I believe it's useful for this to throw a warning, so I added a new macro that's self-documenting that the file will never be unlocked to avoid the warning in the few places where it's wrong.
2012-10-31add dl_iterate_phdr interfaceRich Felker-7/+87
patches by Alex Caudill (npx). the dynamic-linked version is almost identical to the final submitted patch; I just added a couple missing lines for saving the phdr address when the dynamic linker is invoked directly to run a program, and removed a couple to avoid introducing another unnecessary type. the static-linked version is based on npx's draft. it could use some improvements which are contingent on the startup code saving some additional information for later use.
2012-10-19support looking up thread-local objects with dlsymRich Felker-0/+6
2012-10-19fix breakage in dlsym for looking up RTLD_DEFAULT, etc.Rich Felker-2/+5
this was broken during the early dynamic-linked TLS commits, which rearranged some of the code for handling new relocation types.
2012-10-17fix microblaze asm relocations for shared libcRich Felker-3/+3
only @PLT relocations are considered functions for purposes of -Bsymbolic-functions, so always use @PLT. it should not hurt in the static-linked case.
2012-10-15add support for TLS variant I, presently needed for arm and mipsRich Felker-3/+32
despite documentation that makes it sound a lot different, the only ABI-constraint difference between TLS variants II and I seems to be that variant II stores the initial TLS segment immediately below the thread pointer (i.e. the thread pointer points to the end of it) and variant I stores the initial TLS segment above the thread pointer, requiring the thread descriptor to be stored below. the actual value stored in the thread pointer register also tends to have per-arch random offsets applied to it for silly micro-optimization purposes. with these changes applied, TLS should be basically working on all supported archs except microblaze. I'm still working on getting the necessary information and a working toolchain that can build TLS binaries for microblaze, but in theory, static-linked programs with TLS and dynamic-linked programs where only the main executable uses TLS should already work on microblaze. alignment constraints have not yet been heavily tested, so it's possible that this code does not always align TLS segments correctly on archs that need TLS variant I.
2012-10-14fix main program TLS alignment for dynamic-linked programsRich Felker-6/+5
this change brings the behavior in line with the static-linked code, which seems to be correct.
2012-10-13fix namespace clash (libc) in dynlink.cRich Felker-14/+13
this makes it so the #undef libc and __libc name are no longer needed, which were problematic because the "accessor function" mode for accessing the libc struct could not be used, breaking build on any compiler without (working) visibility.
2012-10-13remove dead code from dynamic linkerRich Felker-10/+0
2012-10-07clean up and refactor program initializationRich Felker-2/+2
the code in __libc_start_main is now responsible for parsing auxv, rather than duplicating the parsing all over the place. this should shave off a few cycles and some code size. __init_libc is left as an external-linkage function despite the fact that it could be static, to prevent it from being inlined and permanently wasting stack space when main is called. a few other minor changes are included, like eliminating per-thread ssp canaries (they were likely broken when combined with certain dlopen usages, and completely unnecessary) and some other unnecessary checks. since this code gets linked into every program, it should be as small and simple as possible.
2012-10-07fix breakage due to initializing thread pointer when loading libsRich Felker-1/+1
at initial program load, all libraries must be loaded before the thread pointer can be setup, since the TP-relative addresses of all initial TLS objects must be constant.
2012-10-06make new TLS setup block even implementation-internals signalsRich Felker-2/+1
this is needed to ensure async-cancel-safety, i.e. to make it safe to access TLS objects when async cancellation is enabled. otherwise, if cancellation were acter upon after the atomic fetch/add but before the thread saved the obtained memory, another access to the same TLS in the cancellation handler could end up performing the atomic fetch/add again, consuming more memory than is actually available and overflowing into other objects on the heap.
2012-10-06don't crash if TLS library is loaded into process with no thread pointerRich Felker-0/+5
2012-10-06fix symbol acceptance/rejection rules for TLSRich Felker-8/+14
symbol value of 0 is not "undefined" for TLS; it's the address of the first symbol in the TLS segment. however, non-definition TLS references also have values of 0, so check the section. hopefully the new logic is more clear, too.
2012-10-06TLS fixes, mainly alignment handlingRich Felker-39/+48
compute offsets from the thread pointer statically when loading the library, rather than repeating the logic on each thread creation. not only is the latter less efficient at runtime; it also fails to provide solid guarantees that the offsets will remain the same when the initial alignment of memory is different. the new alignment handling is both more rigorous and simpler. the old code was also clobbering TLS bss with random image data in some cases due to using tls_size (size of TLS segment) instead of tls_len (length of the TLS data image).
2012-10-05fix/improve shared library ctor/dtor handling, allow recursive dlopenRich Felker-7/+29
some libraries call dlopen from their constructors, resulting in recursive calls to dlopen. previously, this resulted in deadlock. I'm now unlocking the dlopen lock before running constructors (this is especially important since the lock also blocked pthread_create and was being held while application code runs!) and using a separate recursive mutex protecting the ctor/dtor state instead. in order to prevent the same ctor from being called more than once, a module is considered "constructed" just before the ctor runs. also, switch from using atexit to register each dtor to using a single atexit call to register the dynamic linker's dtor processing as just one handler. this is necessary because atexit performs allocation and may fail, but the library has already been loaded and cannot be backed-out at the time dtor registration is performed. this change also ensures that all dtors run after all atexit functions, rather than in mixed order.
2012-10-05small dynamic linker module search fixRich Felker-1/+2
libraries loaded more than once by pathname should not get shortnames that would cause them to later be used to satisfy non-pathname load requests.