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musl - an implementation of the standard library for Linux-based systems
f47a8cdd25
when PAGE_SIZE is not constant, internal/libc.h defines it to expand to libc.page_size. however, kernel_mapped_dso, reachable from stage 2 of the dynamic linker bootstrap (__dls2), needs PAGE_SIZE to interpret the relro range. at this point the libc object is both uninitialized and invalid to access according to our model for bootstrapping, which does not assume any external-linkage objects are accessible until stages 2b/3. in practice it likely worked because hidden visibility tends to behave like internal linkage, but this is not a property that the dynamic linker was designed to rely upon. this bug likely manifested as relro malfunction on archs with variable page size, due to incorrect mask when aligning the relro bounds to page boundaries. while there are certainly more direct ways to fix the known problem point here, a maximally future-proof way is to just bypass the libc.h PAGE_SIZE definition in the dynamic linker and instead have dynlink.c define its own internal-linkage object for variable page size. then, if anything else in stage 2 ever ends up referencing PAGE_SIZE, it will just automatically work right. |
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| compat/time32 | ||
| crt | ||
| dist | ||
| include | ||
| ldso | ||
| src | ||
| tools | ||
| .gitignore | ||
| .mailmap | ||
| configure | ||
| COPYRIGHT | ||
| dynamic.list | ||
| INSTALL | ||
| Makefile | ||
| README | ||
| VERSION | ||
| WHATSNEW | ||
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/