9db2541d4c
This adds a specific unwind plan for AArch64 Linux sigreturn frames. Previously we assumed that the fp would be valid here but it is not. https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/vdso/sigreturn.S On Ubuntu Bionic it happened to point to an old frame info which meant you got what looked like a correct backtrace. On Focal, the info is completely invalid. (probably due to some code shuffling in libc) This adds an UnwindPlan that knows that the sp in a sigreturn frame points to an rt_sigframe from which we can offset to get saved sp and pc values to backtrace correctly. Based on LibUnwind's change: https://reviews.llvm.org/D90898 A new test is added that sets all compares the frames from the initial signal catch to the handler break. Ensuring that the stack/frame pointer, function name and register values match. (this test is AArch64 Linux specific because it's the only one with a specific unwind plan for this situation) Fixes https://bugs.llvm.org/show_bug.cgi?id=52165 Reviewed By: omjavaid, labath Differential Revision: https://reviews.llvm.org/D112069