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path: root/src/env/__libc_start_main.c
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2015-04-22fix inconsistent visibility for __hwcap and __sysinfo symbolsRich Felker-3/+0
these are used as hidden by asm files (and such use is the whole reason they exist), but their actual definitions were not hidden.
2014-07-01fix typo in a comment in __libc_start_mainRich Felker-1/+1
2014-05-29support linux kernel apis (new archs) with old syscalls removedRich Felker-0/+5
such archs are expected to omit definitions of the SYS_* macros for syscalls their kernels lack from arch/$ARCH/bits/syscall.h. the preprocessor is then able to select the an appropriate implementation for affected functions. two basic strategies are used on a case-by-case basis: where the old syscalls correspond to deprecated library-level functions, the deprecated functions have been converted to wrappers for the modern function, and the modern function has fallback code (omitted at the preprocessor level on new archs) to make use of the old syscalls if the new syscall fails with ENOSYS. this also improves functionality on older kernels and eliminates the incentive to program with deprecated library-level functions for the sake of compatibility with older kernels. in other situations where the old syscalls correspond to library-level functions which are not deprecated but merely lack some new features, such as the *at functions, the old syscalls are still used on archs which support them. this may change at some point in the future if or when fallback code is added to the new functions to make them usable (possibly with reduced functionality) on old kernels.
2014-05-24support kernels with no SYS_open syscall, only SYS_openatRich Felker-1/+1
open is handled specially because it is used from so many places, in so many variants (2 or 3 arguments, setting errno or not, and cancellable or not). trying to do it as a function would not only increase bloat, but would also risk subtle breakage. this is the first step towards supporting "new" archs where linux lacks "old" syscalls.
2014-04-21make __init_libc static for non-shared libcRich Felker-0/+3
being static allows it to be inlined in __libc_start_main; inlining should take place at all levels since the function is called exactly once. this further reduces mandatory startup code size for static binaries.
2014-04-21further micro-optimize startup code for sizeRich Felker-2/+14
there is no reason (and seemingly there never was any) for __init_security to be its own function. it's linked unconditionally so it can just be placed inline in __init_libc.
2014-04-21micro-optimize some startup code for sizeRich Felker-0/+4
moving the call to __init_ssp from __init_security to __init_libc makes __init_security a leaf function, which allows the compiler to make it smaller. __init_libc is already non-leaf, and the additional call makes no difference to the amount of register spillage. in addition, it really made no sense for the call to __init_ssp to be buried inside __init_security rather than parallel with other init functions.
2014-04-07remove some cruft from libc/tls init codeRich Felker-1/+0
2013-09-15support configurable page size on mips, powerpc and microblazeSzabolcs Nagy-0/+1
PAGE_SIZE was hardcoded to 4096, which is historically what most systems use, but on several archs it is a kernel config parameter, user space can only know it at execution time from the aux vector. PAGE_SIZE and PAGESIZE are not defined on archs where page size is a runtime parameter, applications should use sysconf(_SC_PAGE_SIZE) to query it. Internally libc code defines PAGE_SIZE to libc.page_size, which is set to aux[AT_PAGESZ] in __init_libc and early in __dynlink as well. (Note that libc.page_size can be accessed without GOT, ie. before relocations are done) Some fpathconf settings are hardcoded to 4096, these should be actually queried from the filesystem using statfs.
2013-07-21add support for init/fini array in main program, and greatly simplifyRich Felker-13/+13
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.
2013-04-06add support for program_invocation[_short]_nameRich Felker-2/+8
this is a bit ugly, and the motivation for supporting it is questionable. however the main factors were: 1. it will be useful to have this for certain internal purposes anyway -- things like syslog. 2. applications can just save argv[0] in main, but it's hard to fix non-portable library code that's depending on being able to get the invocation name without the main application's help.
2012-11-30fix ordering of shared library ctors with respect to libc initRich Felker-0/+5
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.
2012-10-11i386 vsyscall support (vdso-provided sysenter/syscall instruction based)Rich Felker-0/+3
this doubles the performance of the fastest syscalls on the atom I tested it on; improvement is reportedly much more dramatic on worst-case cpus. cannot be used for cancellable syscalls.
2012-10-08ensure that buffer for decoding auxv at startup is initially zeroRich Felker-1/+1
2012-10-07clean up and refactor program initializationRich Felker-7/+19
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.
2012-10-04TLS (GNU/C11 thread-local storage) support for static-linked programsRich Felker-0/+2
the design for TLS in dynamic-linked programs is mostly complete too, but I have not yet implemented it. cost is nonzero but still low for programs which do not use TLS and/or do not use threads (a few hundred bytes of new code, plus dependency on memcpy). i believe it can be made smaller at some point by merging __init_tls and __init_security into __libc_start_main and avoiding duplicate auxv-parsing code. at the same time, I've also slightly changed the logic pthread_create uses to allocate guard pages to ensure that guard pages are not counted towards commit charge.
2011-08-23security hardening: ensure suid programs have valid stdin/out/errRich Felker-9/+9
this behavior (opening fds 0-2 for a suid program) is explicitly allowed (but not required) by POSIX to protect badly-written suid programs from clobbering files they later open. this commit does add some cost in startup code, but the availability of auxv and the security flag will be useful elsewhere in the future. in particular auxv is needed for static-linked vdso support, which is still waiting to be committed (sorry nik!)
2011-02-12initial check-in, version 0.5.0v0.5.0Rich Felker-0/+26