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author | Rich Felker <dalias@aerifal.cx> | 2014-11-22 12:26:38 -0500 |
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committer | Rich Felker <dalias@aerifal.cx> | 2014-11-22 12:26:38 -0500 |
commit | 8cd0b11eafeaaec3df5113cb39094e5456ca6b22 (patch) | |
tree | 310e944d94172757e21a27734d4261ee1e6d8cea /src/thread/i386 | |
parent | 4a241f14a6bea81b9b50edda09f8184e35a75860 (diff) | |
download | musl-8cd0b11eafeaaec3df5113cb39094e5456ca6b22.tar.gz musl-8cd0b11eafeaaec3df5113cb39094e5456ca6b22.tar.xz musl-8cd0b11eafeaaec3df5113cb39094e5456ca6b22.zip |
fix __aeabi_read_tp oversight in arm atomics/tls overhaul
calls to __aeabi_read_tp may be generated by the compiler to access TLS on pre-v6 targets. previously, this function was hard-coded to call the kuser helper, which would crash on kernels with kuser helper removed. to fix the problem most efficiently, the definition of __aeabi_read_tp is moved so that it's an alias for the new __a_gettp. however, on v7+ targets, code to initialize the runtime choice of thread-pointer loading code is not even compiled, meaning that defining __aeabi_read_tp would have caused an immediate crash due to using the default implementation of __a_gettp with a HCF instruction. fortunately there is an elegant solution which reduces overall code size: putting the native thread-pointer loading instruction in the default code path for __a_gettp, so that separate default/native code paths are not needed. this function should never be called before __set_thread_area anyway, and if it is called early on pre-v6 hardware, the old behavior (crashing) is maintained. ideally __aeabi_read_tp would not be called at all on v7+ targets anyway -- in fact, prior to the overhaul, the same problem existed, but it was never caught by users building for v7+ with kuser disabled. however, it's possible for calls to __aeabi_read_tp to end up in a v7+ binary if some of the object files were built for pre-v7 targets, e.g. in the case of static libraries that were built separately, so this case needs to be handled.
Diffstat (limited to 'src/thread/i386')
0 files changed, 0 insertions, 0 deletions