Add test and fix ordering of unwinding in _Unwind_Backtrace() (was
unwinding after calling callback, causing _Unwind_Backtrace() to be
included in backtrace).
http://reviews.llvm.org/D5112
Files:
include/unwind.h
src/Unwind/Unwind-EHABI.cpp
src/Unwind/UnwindLevel1-gcc-ext.c
test/backtrace_test.cpp
Index: include/unwind.h
===================================================================
--- include/unwind.h
+++ include/unwind.h
@@ -207,6 +207,7 @@
uint32_t discriminator,
_Unwind_VRS_DataRepresentation representation);
+extern uint32_t* decode_eht_entry(const uint32_t*, size_t*, size_t*);
extern _Unwind_Reason_Code _Unwind_VRS_Interpret(_Unwind_Context *context,
uint32_t *data, size_t offset,
size_t len);
Index: src/Unwind/Unwind-EHABI.cpp
===================================================================
--- src/Unwind/Unwind-EHABI.cpp
+++ src/Unwind/Unwind-EHABI.cpp
@@ -167,24 +167,13 @@
struct _Unwind_Context* context) {
// Read the compact model EHT entry's header # 6.3
uint32_t* unwindingData = ucbp->pr_cache.ehtp;
- uint32_t unwindInfo = *unwindingData;
- assert((unwindInfo & 0xf0000000) == 0x80000000 && "Must be a compact entry");
Descriptor::Format format =
- static_cast<Descriptor::Format>((unwindInfo & 0x0f000000) >> 24);
+ static_cast<Descriptor::Format>((*unwindingData & 0x0f000000) >> 24);
size_t len = 0;
- size_t startOffset = 0;
- switch (format) {
- case Descriptor::SU16:
- len = 4;
- startOffset = 1;
- break;
- case Descriptor::LU16:
- case Descriptor::LU32:
- len = 4 + 4 * ((unwindInfo & 0x00ff0000) >> 16);
- startOffset = 2;
- break;
- default:
- return _URC_FAILURE;
+ size_t off = 0;
+ unwindingData = decode_eht_entry(unwindingData, &off, &len);
+ if (unwindingData == nullptr) {
+ return _URC_FAILURE;
}
// Handle descriptors before unwinding so they are processed in the context
@@ -198,7 +187,7 @@
if (result != _URC_CONTINUE_UNWIND)
return result;
- return _Unwind_VRS_Interpret(context, unwindingData, startOffset, len);
+ return _Unwind_VRS_Interpret(context, unwindingData, off, len);
}
// Generates mask discriminator for _Unwind_VRS_Pop, e.g. for _UVRSC_CORE /
@@ -215,6 +204,43 @@
} // end anonymous namespace
+/**
+ * Decodes an EHT entry.
+ *
+ * @param data Pointer to EHT.
+ * @param[out] off Offset from return value (in bytes) to begin interpretation.
+ * @param[out] len Number of bytes in unwind code.
+ * @return Pointer to beginning of unwind code.
+ */
+extern "C" uint32_t*
+decode_eht_entry(const uint32_t* data, size_t* off, size_t* len) {
+ if ((*data & 0x80000000) == 0) {
+ // 6.2: Generic Model
+ *off = 1; // First byte is size data.
+ *len = (((data[1] >> 24) & 0xff) + 1) * 4;
+ data++; // Skip the first word, which is the prel31 offset.
+ } else {
+ // 6.3: ARM Compact Model
+ Descriptor::Format format =
+ static_cast<Descriptor::Format>((*data & 0x0f000000) >> 24);
+ switch (format) {
+ case Descriptor::SU16:
+ *len = 4;
+ *off = 1;
+ break;
+ case Descriptor::LU16:
+ case Descriptor::LU32:
+ *len = 4 + 4 * ((*data & 0x00ff0000) >> 16);
+ *off = 2;
+ break;
+ default:
+ return nullptr;
+ }
+ }
+
+ return const_cast<uint32_t*>(data);
+}
+
_Unwind_Reason_Code _Unwind_VRS_Interpret(
_Unwind_Context* context,
uint32_t* data,
Index: src/Unwind/UnwindLevel1-gcc-ext.c
===================================================================
--- src/Unwind/UnwindLevel1-gcc-ext.c
+++ src/Unwind/UnwindLevel1-gcc-ext.c
@@ -109,6 +109,28 @@
// walk each frame
while (true) {
+ _Unwind_Reason_Code result;
+#if LIBCXXABI_ARM_EHABI
+ // Get the information for this frame.
+ unw_proc_info_t frameInfo;
+ if (unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
+ return _URC_END_OF_STACK;
+ }
+
+ struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
+ size_t off;
+ size_t len;
+ uint32_t* unwindInfo = (uint32_t *) frameInfo.unwind_info;
+ unwindInfo = decode_eht_entry(unwindInfo, &off, &len);
+ if (unwindInfo == NULL) {
+ return _URC_FAILURE;
+ }
+
+ result = _Unwind_VRS_Interpret(context, unwindInfo, off, len);
+ if (result != _URC_CONTINUE_UNWIND) {
+ return _URC_END_OF_STACK;
+ }
+#endif // LIBCXXABI_ARM_EHABI
// ask libuwind to get next frame (skip over first frame which is
// _Unwind_Backtrace())
@@ -133,8 +155,7 @@
}
// call trace function with this frame
- _Unwind_Reason_Code result =
- (*callback)((struct _Unwind_Context *)(&cursor), ref);
+ result = (*callback)((struct _Unwind_Context *)(&cursor), ref);
if (result != _URC_NO_REASON) {
_LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because callback "
"returned %d\n",
Index: test/backtrace_test.cpp
===================================================================
--- /dev/null
+++ test/backtrace_test.cpp
@@ -0,0 +1,61 @@
+//===---------------------- backtrace_test.cpp ----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include <assert.h>
+#include <unwind.h>
+
+extern "C" _Unwind_Reason_Code
+trace_function(struct _Unwind_Context* context, void* ntraced) {
+ (*reinterpret_cast<size_t*>(ntraced))++;
+ // We should never have a call stack this deep...
+ assert(*reinterpret_cast<size_t*>(ntraced) < 20);
+ return _URC_NO_REASON;
+}
+
+void call3_throw(size_t* ntraced) {
+ try {
+ _Unwind_Backtrace(trace_function, ntraced);
+ } catch (...) {
+ assert(false);
+ }
+}
+
+void call3_nothrow(size_t* ntraced) {
+ _Unwind_Backtrace(trace_function, ntraced);
+}
+
+void call2(size_t* ntraced, bool do_throw) {
+ if (do_throw) {
+ call3_throw(ntraced);
+ } else {
+ call3_nothrow(ntraced);
+ }
+}
+
+void call1(size_t* ntraced, bool do_throw) {
+ call2(ntraced, do_throw);
+}
+
+int main() {
+ size_t throw_ntraced = 0;
+ size_t nothrow_ntraced = 0;
+
+ call1(¬hrow_ntraced, false);
+
+ try {
+ call1(&throw_ntraced, true);
+ } catch (...) {
+ assert(false);
+ }
+
+ // Can we be more precise? Will the number of traces be the same on all
+ // platforms?
+ assert(nothrow_ntraced > 1);
+ assert(throw_ntraced == nothrow_ntraced); // Make sure we unwind through catch
+ return 0;
+}
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