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c82deed676
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
47 lines
1.3 KiB
C++
47 lines
1.3 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// Ensure that the unwinder can cope with the signal handler.
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// REQUIRES: linux && (target-aarch64 || target-x86_64)
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#include <assert.h>
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#include <dlfcn.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <unwind.h>
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_Unwind_Reason_Code frame_handler(struct _Unwind_Context* ctx, void* arg) {
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(void)arg;
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Dl_info info = { 0, 0, 0, 0 };
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// Unwind util the main is reached, above frames depend on the platform and
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// architecture.
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if (dladdr(reinterpret_cast<void *>(_Unwind_GetIP(ctx)), &info) &&
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info.dli_sname && !strcmp("main", info.dli_sname)) {
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_Exit(0);
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}
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return _URC_NO_REASON;
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}
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void signal_handler(int signum) {
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(void)signum;
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_Unwind_Backtrace(frame_handler, NULL);
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_Exit(-1);
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}
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int main(int, char**) {
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signal(SIGUSR1, signal_handler);
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kill(getpid(), SIGUSR1);
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return -2;
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}
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