Add a new unwind method on error.
If a function crashes by jumping into unexecutable code, the old method
could not unwind through that. Add a fallback method to set the pc from
the default return address location.
In addition, add a new finished check for steps. This will provide a method
to indicate that this step is the last step. This prevents cases where
the fallback method might be triggered incorrectly.
Update the libbacktrace code to unwind using the new methodology.
Update the unwind tool to use the new unwind methodology.
Add a new option to crasher that calls through a null function.
Create a new object, Unwinder, that encapsulates the a basic unwind. For now,
libbacktrace will still use the custom code.
Added new unit tests to cover the new cases. Also add a test that
crashes calling a nullptr as a function, and then has call frames in
the signal stack.
Bug: 65842173
Test: Pass all unit tests, verify crasher dumps properly.
Change-Id: Ia18430ab107e9f7bdf0e14a9b74710b1280bd7f4
diff --git a/libunwindstack/tools/unwind.cpp b/libunwindstack/tools/unwind.cpp
index 3614198..faac2ef 100644
--- a/libunwindstack/tools/unwind.cpp
+++ b/libunwindstack/tools/unwind.cpp
@@ -26,7 +26,11 @@
#include <sys/types.h>
#include <unistd.h>
+#include <memory>
#include <string>
+#include <vector>
+
+#include <android-base/stringprintf.h>
#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
@@ -55,6 +59,62 @@
return ptrace(PTRACE_DETACH, pid, 0, 0) == 0;
}
+std::string GetFrameInfo(size_t frame_num, unwindstack::Regs* regs,
+ const std::shared_ptr<unwindstack::Memory>& process_memory,
+ unwindstack::MapInfo* map_info, uint64_t* rel_pc) {
+ bool bits32;
+ switch (regs->MachineType()) {
+ case EM_ARM:
+ case EM_386:
+ bits32 = true;
+ break;
+
+ default:
+ bits32 = false;
+ }
+
+ if (map_info == nullptr) {
+ if (bits32) {
+ return android::base::StringPrintf(" #%02zu pc %08" PRIx64, frame_num, regs->pc());
+ } else {
+ return android::base::StringPrintf(" #%02zu pc %016" PRIx64, frame_num, regs->pc());
+ }
+ }
+
+ unwindstack::Elf* elf = map_info->GetElf(process_memory, true);
+ *rel_pc = elf->GetRelPc(regs->pc(), map_info);
+ uint64_t adjusted_rel_pc = *rel_pc;
+ // Don't need to adjust the first frame pc.
+ if (frame_num != 0) {
+ adjusted_rel_pc = regs->GetAdjustedPc(*rel_pc, elf);
+ }
+
+ std::string line;
+ if (bits32) {
+ line = android::base::StringPrintf(" #%02zu pc %08" PRIx64, frame_num, adjusted_rel_pc);
+ } else {
+ line = android::base::StringPrintf(" #%02zu pc %016" PRIx64, frame_num, adjusted_rel_pc);
+ }
+ if (!map_info->name.empty()) {
+ line += " " + map_info->name;
+ if (map_info->elf_offset != 0) {
+ line += android::base::StringPrintf(" (offset 0x%" PRIx64 ")", map_info->elf_offset);
+ }
+ } else {
+ line += android::base::StringPrintf(" <anonymous:%" PRIx64 ">", map_info->offset);
+ }
+ uint64_t func_offset;
+ std::string func_name;
+ if (elf->GetFunctionName(adjusted_rel_pc, &func_name, &func_offset)) {
+ line += " (" + func_name;
+ if (func_offset != 0) {
+ line += android::base::StringPrintf("+%" PRId64, func_offset);
+ }
+ line += ')';
+ }
+ return line;
+}
+
void DoUnwind(pid_t pid) {
unwindstack::RemoteMaps remote_maps(pid);
if (!remote_maps.Parse()) {
@@ -68,7 +128,6 @@
return;
}
- bool bits32 = true;
printf("ABI: ");
switch (regs->MachineType()) {
case EM_ARM:
@@ -79,11 +138,9 @@
break;
case EM_AARCH64:
printf("arm64");
- bits32 = false;
break;
case EM_X86_64:
printf("x86_64");
- bits32 = false;
break;
default:
printf("unknown\n");
@@ -92,52 +149,48 @@
printf("\n");
auto process_memory = unwindstack::Memory::CreateProcessMemory(pid);
+ bool return_address_attempt = false;
+ std::vector<std::string> frames;
for (size_t frame_num = 0; frame_num < 64; frame_num++) {
- if (regs->pc() == 0) {
- break;
- }
unwindstack::MapInfo* map_info = remote_maps.Find(regs->pc());
+ uint64_t rel_pc;
+ frames.push_back(GetFrameInfo(frame_num, regs, process_memory, map_info, &rel_pc));
+ bool stepped;
if (map_info == nullptr) {
- printf("Failed to find map data for the pc\n");
- break;
- }
-
- unwindstack::Elf* elf = map_info->GetElf(process_memory, true);
-
- uint64_t rel_pc = elf->GetRelPc(regs->pc(), map_info);
- uint64_t adjusted_rel_pc = rel_pc;
- // Don't need to adjust the first frame pc.
- if (frame_num != 0) {
- adjusted_rel_pc = regs->GetAdjustedPc(rel_pc, elf);
- }
-
- std::string name;
- if (bits32) {
- printf(" #%02zu pc %08" PRIx64, frame_num, adjusted_rel_pc);
+ stepped = false;
} else {
- printf(" #%02zu pc %016" PRIx64, frame_num, adjusted_rel_pc);
+ bool finished;
+ stepped =
+ map_info->elf->Step(rel_pc + map_info->elf_offset, regs, process_memory.get(), &finished);
+ if (stepped && finished) {
+ break;
+ }
}
- if (!map_info->name.empty()) {
- printf(" %s", map_info->name.c_str());
- if (map_info->elf_offset != 0) {
- printf(" (offset 0x%" PRIx64 ")", map_info->elf_offset);
+ if (!stepped) {
+ if (return_address_attempt) {
+ // We tried the return address and it didn't work, remove the last
+ // two frames. If this bad frame is the only frame, only remove
+ // the last frame.
+ frames.pop_back();
+ if (frame_num != 1) {
+ frames.pop_back();
+ }
+ break;
+ } else {
+ // Steping didn't work, try this secondary method.
+ if (!regs->SetPcFromReturnAddress(process_memory.get())) {
+ break;
+ }
+ return_address_attempt = true;
}
} else {
- printf(" <anonymous:%" PRIx64 ">", map_info->offset);
+ return_address_attempt = false;
}
- uint64_t func_offset;
- if (elf->GetFunctionName(adjusted_rel_pc, &name, &func_offset)) {
- printf(" (%s", name.c_str());
- if (func_offset != 0) {
- printf("+%" PRId64, func_offset);
- }
- printf(")");
- }
- printf("\n");
+ }
- if (!elf->Step(rel_pc + map_info->elf_offset, regs, process_memory.get())) {
- break;
- }
+ // Print the frames.
+ for (auto& frame : frames) {
+ printf("%s\n", frame.c_str());
}
}