Tracking the new bug here now: https://sourceware.org/bugzilla/show_bug.cgi?id=26141
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to binutils in Ubuntu. https://bugs.launchpad.net/bugs/725126 Title: gas may assemble b to locally-defined, preemptible global symbol as "b.n" Status in binutils: Fix Released Status in Linaro Binutils: Won't Fix Status in Cortex String Routines: Invalid Status in armel-cross-toolchain-base package in Ubuntu: Fix Released Status in binutils package in Ubuntu: Fix Released Bug description: There's no guarantee that R_ARM_THM_JUMP11 relocation can be resolved correctly if the symbol gets preempted. Observed in binutils-arm-linux-gnueabi 2.20.51.20100908-0ubuntu2cross1.52. Observed on binutils trunk on 2011-02-25. The problem seems to strike when the compiler optimises a sibling call to "b <label>", for which the assembler generates a b.n. As a side-effect of the presence of this relocation, Thumb-2 kernel modules may fail to load, since the kernel doesn't support fixing up this relocation. I believe the kernel doesn't do any symbol preemption processing when loading modules -- if so, the relocation is actually redundant. But there's no way for the kernel to detect at module load time that the relocation can safely be ignored. In kernel builds, about 1 out every 6 modules suffers from this problem. It's not clear to me whether the method used by the kernel to link .ko objects is wrong or not. It seems that either the tools should support symbol preemption in this scenario (implying that a short branch is not adequate to guarantee that preemption will work -- i.e., a gas bug) or not (in this case the fixup should be done locally and there should presumably be no relocation -- i.e., a different gas bug). It appears that passing -fno-optimize-sibling-calls to GCC can work around the problem by avoiding the generation of local branches to global symbols, but this is clearly not the correct fix. To manage notifications about this bug go to: https://bugs.launchpad.net/binutils/+bug/725126/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
