1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10// Ensure that leaf function can be unwund.
11// REQUIRES: target={{(aarch64|loongarch64|riscv64|s390x|x86_64)-.+linux.*}}
12
13// TODO: Figure out why this fails with Memory Sanitizer.
14// XFAIL: msan
15
16// Note: this test fails on musl because:
17//
18// (a) musl disables emission of unwind information for its build, and
19// (b) musl's signal trampolines don't include unwind information
20//
21// XFAIL: target={{.*}}-musl
22
23#undef NDEBUG
24#include <assert.h>
25#include <signal.h>
26#include <stdio.h>
27#include <stdlib.h>
28#include <string.h>
29#include <sys/types.h>
30#include <unistd.h>
31#include <unwind.h>
32
33// Using __attribute__((section("main_func"))) is ELF specific, but then
34// this entire test is marked as requiring Linux, so we should be good.
35//
36// We don't use dladdr() because on musl it's a no-op when statically linked.
37extern char __start_main_func;
38extern char __stop_main_func;
39
40_Unwind_Reason_Code frame_handler(struct _Unwind_Context* ctx, void* arg) {
41 (void)arg;
42
43 // Unwind until the main is reached, above frames depend on the platform and
44 // architecture.
45 uintptr_t ip = _Unwind_GetIP(ctx);
46 if (ip >= (uintptr_t)&__start_main_func &&
47 ip < (uintptr_t)&__stop_main_func) {
48 _Exit(status: 0);
49 }
50
51 return _URC_NO_REASON;
52}
53
54void signal_handler(int signum) {
55 (void)signum;
56 _Unwind_Backtrace(frame_handler, NULL);
57 _Exit(status: -1);
58}
59
60__attribute__((noinline)) void crashing_leaf_func(int do_trap) {
61 // libunwind searches for the address before the return address which points
62 // to the trap instruction. We make the trap conditional and prevent inlining
63 // of the function to ensure that the compiler doesn't remove the `ret`
64 // instruction altogether.
65 //
66 // It's also important that the trap instruction isn't the first instruction
67 // in the function (which it isn't because of the branch) for other unwinders
68 // that also decrement pc.
69 if (do_trap)
70 __builtin_trap();
71}
72
73__attribute__((section("main_func"))) int main(int, char **) {
74 signal(SIGTRAP, handler: signal_handler);
75 signal(SIGILL, handler: signal_handler);
76 crashing_leaf_func(do_trap: 1);
77 return -2;
78}
79

source code of libunwind/test/unwind_leaffunction.pass.cpp