[libunwind] Unwind through aarch64/Linux sigreturn frame
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
GitOrigin-RevId: c82deed6764cbc63966374baf9721331901ca958
diff --git a/test/signal_unwind.pass.cpp b/test/signal_unwind.pass.cpp
index 25ff0bb..3acd772 100644
--- a/test/signal_unwind.pass.cpp
+++ b/test/signal_unwind.pass.cpp
@@ -8,7 +8,7 @@
//===----------------------------------------------------------------------===//
// Ensure that the unwinder can cope with the signal handler.
-// REQUIRES: x86_64-linux
+// REQUIRES: linux && (target-aarch64 || target-x86_64)
#include <assert.h>
#include <dlfcn.h>
@@ -23,10 +23,11 @@
_Unwind_Reason_Code frame_handler(struct _Unwind_Context* ctx, void* arg) {
(void)arg;
Dl_info info = { 0, 0, 0, 0 };
- assert(dladdr((void*)_Unwind_GetIP(ctx), &info));
- // Unwind util the main is reached, above frames deeped on the platfrom and architecture.
- if(info.dli_sname && !strcmp("main", info.dli_sname)) {
+ // Unwind util the main is reached, above frames depend on the platform and
+ // architecture.
+ if (dladdr(reinterpret_cast<void *>(_Unwind_GetIP(ctx)), &info) &&
+ info.dli_sname && !strcmp("main", info.dli_sname)) {
_Exit(0);
}
return _URC_NO_REASON;