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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 | ||