path: root/src
diff options
authorRich Felker <>2014-11-22 12:26:38 -0500
committerRich Felker <>2014-11-22 12:26:38 -0500
commit8cd0b11eafeaaec3df5113cb39094e5456ca6b22 (patch)
tree310e944d94172757e21a27734d4261ee1e6d8cea /src
parent4a241f14a6bea81b9b50edda09f8184e35a75860 (diff)
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')
1 files changed, 0 insertions, 4 deletions
diff --git a/src/thread/arm/tls.s b/src/thread/arm/tls.s
deleted file mode 100644
index 59736ac2..00000000
--- a/src/thread/arm/tls.s
+++ /dev/null
@@ -1,4 +0,0 @@ __aeabi_read_tp
-.type __aeabi_read_tp,%function
- ldr pc,=0xffff0fe0