Hi jroelofs,
Since the personality functions do the actual unwinding on ARM, and will
also stop unwinding when they encounter a handler, we invoke
_Unwind_VRS_Interpret() directly form _Unwind_Backtrace().
To simplify, the logic for decoding an EHT is moved out of
unwindOneFrame() and into its own function, decode_eht_entry(). Unlike
unwindOneFrame(), which could only handle ARM's compact personality
function entries (section 6.3) decode_eht_entry() can handle the generic
entries (section 6.2).
http://reviews.llvm.org/D5112
Files:
include/unwind.h
src/Unwind/Unwind-EHABI.cpp
src/Unwind/UnwindLevel1-gcc-ext.c
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
@@ -141,6 +141,28 @@
result);
return 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
}
}
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