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An AArch64 sigreturn trampoline frame can't currently be described in a DWARF .eh_frame section, because the AArch64 DWARF spec currently doesn't define a constant for the PC register. (PC and LR may need to be restored to different values.) Instead, use the same technique as libgcc or github.com/libunwind and detect the sigreturn frame by looking for the sigreturn instructions: mov x8, #0x8b svc #0x0 If a sigreturn frame is detected, libunwind restores all the GPRs by assuming that sp points at an rt_sigframe Linux kernel struct. This behavior is a fallback mode that is only used if there is no ordinary unwind info for sigreturn. If libunwind can't find unwind info for a PC, it assumes that the PC is readable, and would crash if it isn't. This could happen if: - The PC points at a function compiled without unwind info, and which is part of an execute-only mapping (e.g. using -Wl,--execute-only). - The PC is invalid and happens to point to unreadable or unmapped memory. In the tests, ignore a failed dladdr call so that the tests can run on user-mode qemu for AArch64, which uses a stack-allocated trampoline instead of a vDSO. Reviewed By: danielkiss, compnerd, #libunwind Differential Revision: https://reviews.llvm.org/D90898 |
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.. | ||
libunwind | ||
alignment.compile.pass.cpp | ||
CMakeLists.txt | ||
frameheadercache_test.pass.cpp | ||
libunwind_01.pass.cpp | ||
libunwind_02.pass.cpp | ||
lit.cfg.py | ||
lit.site.cfg.in | ||
remember_state_leak.pass.sh.s | ||
signal_frame.pass.cpp | ||
signal_unwind.pass.cpp | ||
unw_getcontext.pass.cpp | ||
unwind_leaffunction.pass.cpp |