Hi danalbert, rengolin, jroelofs,
If libcxxabi is compiled as a shared library, and the
executable references the user-defined personality routines
(e.g. __gxx_personality_v0), then the pointer comparison in
Unwind-EHABI.cpp won't work. This is due to the fact that
the PREL31 will point to the PLT stubs for the personality
routines (in the executable), while the __gxx_personality_v0
symbol reference is yet another (different) PLT stub (in the
libunwind.)
This will cause _Unwind_Backtrace() stops to unwind the frame
whenever it reaches __gxx_personality_v0(). This CL fix the
problem by calling the user-defined personality routines
with an undocumented API for force unwinding.
http://reviews.llvm.org/D7032
Files:
src/Unwind/Unwind-EHABI.cpp
src/Unwind/UnwindLevel1-gcc-ext.c
EMAIL PREFERENCES
http://reviews.llvm.org/settings/panel/emailpreferences/
Index: src/Unwind/Unwind-EHABI.cpp
===================================================================
--- src/Unwind/Unwind-EHABI.cpp
+++ src/Unwind/Unwind-EHABI.cpp
@@ -162,10 +162,9 @@
return _URC_CONTINUE_UNWIND;
}
-_Unwind_Reason_Code unwindOneFrame(
- _Unwind_State state,
- _Unwind_Control_Block* ucbp,
- struct _Unwind_Context* context) {
+static _Unwind_Reason_Code unwindOneFrame(_Unwind_State state,
+ _Unwind_Control_Block* ucbp,
+ struct _Unwind_Context* context) {
// Read the compact model EHT entry's header # 6.3
const uint32_t* unwindingData = ucbp->pr_cache.ehtp;
assert((*unwindingData & 0xf0000000) == 0x80000000 && "Must be a compact entry");
@@ -216,44 +215,27 @@
*/
extern "C" const uint32_t*
decode_eht_entry(const uint32_t* data, size_t* off, size_t* len) {
- if ((*data & 0x80000000) == 0) {
- // 6.2: Generic Model
- // EHT entry is a prel31 pointing to the PR, followed by data understood only
- // by the personality routine. Since EHABI doesn't guarantee the location or
- // availability of the unwind opcodes in the generic model, we have to check
- // for them on a case-by-case basis:
- _Unwind_Reason_Code __gxx_personality_v0(int version, _Unwind_Action actions,
- uint64_t exceptionClass,
- _Unwind_Exception* unwind_exception,
- _Unwind_Context* context);
- void *PR = (void*)signExtendPrel31(*data);
- if (PR == (void*)&__gxx_personality_v0) {
- *off = 1; // First byte is size data.
- *len = (((data[1] >> 24) & 0xff) + 1) * 4;
- } else
+ assert((*data & 0x80000000) != 0 &&
+ "decode_eht_entry() does not support user-defined personality");
+
+ // 6.3: ARM Compact Model
+ // EHT entries here correspond to the __aeabi_unwind_cpp_pr[012] PRs indeded
+ // by format:
+ 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;
- data++; // Skip the first word, which is the prel31 offset.
- } else {
- // 6.3: ARM Compact Model
- // EHT entries here correspond to the __aeabi_unwind_cpp_pr[012] PRs indeded
- // by format:
- 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 data;
}
Index: src/Unwind/UnwindLevel1-gcc-ext.c
===================================================================
--- src/Unwind/UnwindLevel1-gcc-ext.c
+++ src/Unwind/UnwindLevel1-gcc-ext.c
@@ -99,6 +99,13 @@
return NULL;
}
+#if LIBCXXABI_ARM_EHABI
+static inline uint32_t readPREL31(const uint32_t *data) {
+ uint32_t base = (uintptr_t) data;
+ uint32_t off = *data | ((0x40000000 & *data) << 1);
+ return (base + off);
+}
+#endif // LIBCXXABI_ARM_EHABI
/// Walk every frame and call trace function at each one. If trace function
/// returns anything other than _URC_NO_REASON, then walk is terminated.
@@ -132,17 +139,43 @@
}
struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
- size_t off;
- size_t len;
const 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;
+ if ((*unwindInfo & 0x80000000) == 0) {
+ // 6.2: Generic Model
+ // EHT entry is a prel31 pointing to the PR, followed by data understood
+ // only by the personality routine. Since EHABI doesn't guarantee the
+ // location or availability of the unwind opcodes in the generic model,
+ // we have to use an undocumented API of personality functions.
+
+ // Create a mock exception object for force unwinding.
+ _Unwind_Exception ex;
+ ex.exception_class = 0x434C4E47554E5700; // CLNGUNW\0
+ ex.pr_cache.fnstart = frameInfo.start_ip;
+ ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
+ ex.pr_cache.additional= frameInfo.flags;
+
+ // Get and call the personality function to unwind the frame.
+ typedef _Unwind_Reason_Code __personality_routine(_Unwind_State,
+ _Unwind_Exception*,
+ _Unwind_Context*);
+ __personality_routine *pr =
+ (__personality_routine *) readPREL31(unwindInfo);
+
+ const _Unwind_State _US_FORCE_UNWIND = 8u;
+ if (pr(_US_FORCE_UNWIND, &ex, context) != _URC_CONTINUE_UNWIND) {
+ return _URC_END_OF_STACK;
+ }
+ } else {
+ size_t off, len;
+ 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
_______________________________________________
cfe-commits mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
