Szabolcs NagyandRich Felker
204a69d2d9
There are two main abi variants for thread local storage layout: (1) TLS is above the thread pointer at a fixed offset and the pthread struct is below that. So the end of the struct is at known offset. (2) the thread pointer points to the pthread struct and TLS starts below it. So the start of the struct is at known (zero) offset. Assembly code for the dynamic TLSDESC callback needs to access the dynamic thread vector (dtv) pointer which is currently at the front of the pthread struct. So in case of (1) the asm code needs to hard code the offset from the end of the struct which can easily break if the struct changes. This commit adds a copy of the dtv at the end of the struct. New members must not be added after dtv_copy, only before it. The size of the struct is increased a bit, but there is opportunity for size optimizations.
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/