jyapayne/musl
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions
No description http://www.etalabs.net/musl/
2,571 commits 1 branch 0 tags 4.2 MiB
Find a file
Rich Felker 2d8cc92a7c fix regression in mips dynamic linker 
this issue caused the address of functions in shared libraries to
resolve to their PLT thunks in the main program rather than their
correct addresses. it was observed causing crashes, though the
mechanism of the crash was not thoroughly investigated. since the
issue is very subtle, it calls for some explanation:

on all well-behaved archs, GOT entries that belong to the PLT use a
special relocation type, typically called JMP_SLOT, so that the
dynamic linker can avoid having the jump destinations for the PLT
resolve to PLT thunks themselves (they also provide a definition for
the symbol, which must be used whenever the address of the function is
taken so that all DSOs see the same address).

however, the traditional mips PIC ABI lacked such a JMP_SLOT
relocation type, presumably because, due to the way PIC works, the
address of the PLT thunk was never needed and could always be ignored.

prior to commit adf94c1966, the mips
version of reloc.h contained a hack that caused all symbol lookups to
be treated like JMP_SLOT, inhibiting undefined symbols from ever being
used to resolve symbolic relocations. this hack goes all the way back
to commit babf820180, when the mips
dynamic linker was first made usable.

during the recent refactoring to eliminate arch-specific relocation
processing (commit adf94c1966), this
hack was overlooked and no equivalent functionality was provided in
the new code.

fixing the problem is not as simple as adding back an equivalent hack,
since there is now also a "non-PIC ABI" that can be used for the main
executable, which actually does use a PLT. the closest thing to
official documentation I could find for this ABI is nonpic.txt,
attached to Message-ID: 20080701202236.GA1534@caradoc.them.org, which
can be found in the gcc mailing list archives and elsewhere. per this
document, undefined symbols corresponding to PLT thunks have the
STO_MIPS_PLT bit set in the symbol's st_other field. thus, I have
added an arch-specific rule for mips, applied at the find_sym level
rather than the relocation level, to reject undefined symbols with the
STO_MIPS_PLT bit clear.

the previous hack of treating all mips relocations as JMP_SLOT-like,
rather than rejecting the unwanted symbols in find_sym, probably also
caused dlsym to wrongly return PLT thunks in place of the correct
address of a function under at least some conditions. this should now
be fixed, at least for global-scope symbol lookups.
2014-06-30 01:18:14 -04:00
arch fix regression in mips dynamic linker 2014-06-30 01:18:14 -04:00
crt superh port 2014-02-23 16:15:54 -06:00
dist add another example option to dist/config.mak 2012-04-24 16:49:11 -04:00
include implement fmtmsg function 2014-06-21 19:24:15 -04:00
lib new solution for empty lib dir (old one had some problems) 2011-02-17 17:12:52 -05:00
src fix regression in mips dynamic linker 2014-06-30 01:18:14 -04:00
tools fix system breakage window during make install due to permissions 2014-01-15 22:29:13 -05:00
.gitignore add version.h to .gitignore; it is a generated file 2014-01-21 01:06:42 -05:00
configure remove optimization-inhibiting behavior from configure's --enable-debug 2014-06-20 16:10:48 -04:00
COPYRIGHT update COPYRIGHT file with additional contributor information 2014-03-20 00:34:19 -04:00
INSTALL add note to INSTALL file about gcc 4.9.0 not being supported 2014-06-25 14:16:15 -04:00
Makefile add tarball-producing targets to Makefile for ease of release 2014-06-25 16:14:37 -04:00
README update version reference in the README file 2014-06-25 14:16:53 -04:00
VERSION release 1.1.3 2014-06-25 16:18:05 -04:00
WHATSNEW release 1.1.3 2014-06-25 16:18:05 -04:00

README 

    musl libc

musl, pronounced like the word "mussel", is an MIT-licensed
implementation of the standard C library targetting the Linux syscall
API, suitable for use in a wide range of deployment environments. musl
offers efficient static and dynamic linking support, lightweight code
and low runtime overhead, strong fail-safe guarantees under correct
usage, and correctness in the sense of standards conformance and
safety. musl is built on the principle that these goals are best
achieved through simple code that is easy to understand and maintain.

The 1.1 release series for musl features coverage for all interfaces
defined in ISO C99 and POSIX 2008 base, along with a number of
non-standardized interfaces for compatibility with Linux, BSD, and
glibc functionality.

For basic installation instructions, see the included INSTALL file.
Information on full musl-targeted compiler toolchains, system
bootstrapping, and Linux distributions built on musl can be found on
the project website:

    http://www.musl-libc.org/