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Force unwind frame with user-defined personality.

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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.

llvm-svn: 226822
This commit is contained in:
Logan Chien 2015-01-22 13:38:11 +00:00
parent d38af30b74
commit 6b2c971524
4 changed files with 109 additions and 69 deletions
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70
libcxxabi/src/Unwind/Unwind-EHABI.cpp
View File

@ -10,6 +10,8 @@
//
//===----------------------------------------------------------------------===//
#include "Unwind-EHABI.h"
#include <unwind.h>
#include <stdbool.h>
@ -44,10 +46,6 @@ const char* getNextNibble(const char* data, uint32_t* out) {
return data + 2;
}
static inline uint32_t signExtendPrel31(uint32_t data) {
return data | ((data & 0x40000000u) << 1);
}
struct Descriptor {
// See # 9.2
typedef enum {
@ -162,10 +160,9 @@ _Unwind_Reason_Code ProcessDescriptors(
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 +213,27 @@ uint32_t RegisterRange(uint8_t start, uint8_t count_minus_one) {
*/
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
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;
}
}
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;
}
return data;
}

45
libcxxabi/src/Unwind/Unwind-EHABI.h Normal file
View File

@ -0,0 +1,45 @@
//===------------------------- Unwind-EHABI.hpp ---------------------------===//
//
// 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.
//
//
//===----------------------------------------------------------------------===//
#ifndef __UNWIND_EHABI_H__
#define __UNWIND_EHABI_H__
#include <stdint.h>
#include <unwind.h>
// Unable to unwind in the ARM index table (section 5 EHABI).
#define UNW_EXIDX_CANTUNWIND 0x1
static inline uint32_t signExtendPrel31(uint32_t data) {
return data | ((data & 0x40000000u) << 1);
}
static inline uint32_t readPrel31(const uint32_t *data) {
return (((uint32_t) data) + signExtendPrel31(*data));
}
#if defined(__cplusplus)
extern "C" {
#endif
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr0(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr1(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr2(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
#if defined(__cplusplus)
} // extern "C"
#endif
#endif // __UNWIND_EHABI_H__

18
libcxxabi/src/Unwind/UnwindCursor.hpp
View File

@ -31,6 +31,10 @@
#include "CompactUnwinder.hpp"
#include "config.h"
#if LIBCXXABI_ARM_EHABI
#include "Unwind-EHABI.h"
#endif
namespace libunwind {
#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
@ -605,20 +609,6 @@ struct EHABIIndexEntry {
uint32_t data;
};
// Unable to unwind in the ARM index table (section 5 EHABI).
#define UNW_EXIDX_CANTUNWIND 0x1
static inline uint32_t signExtendPrel31(uint32_t data) {
return data | ((data & 0x40000000u) << 1);
}
extern "C" _Unwind_Reason_Code __aeabi_unwind_cpp_pr0(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
extern "C" _Unwind_Reason_Code __aeabi_unwind_cpp_pr1(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
extern "C" _Unwind_Reason_Code __aeabi_unwind_cpp_pr2(
_Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
template<typename A>
struct EHABISectionIterator {
typedef EHABISectionIterator _Self;

45
libcxxabi/src/Unwind/UnwindLevel1-gcc-ext.c
View File

@ -21,6 +21,10 @@
#include "libunwind_ext.h"
#include "config.h"
#if LIBCXXABI_ARM_EHABI
#include "Unwind-EHABI.h"
#endif
#if _LIBUNWIND_BUILD_ZERO_COST_APIS
/// Called by __cxa_rethrow().
@ -99,7 +103,6 @@ _LIBUNWIND_EXPORT void *_Unwind_FindEnclosingFunction(void *pc) {
return NULL;
}
/// Walk every frame and call trace function at each one. If trace function
/// returns anything other than _URC_NO_REASON, then walk is terminated.
_LIBUNWIND_EXPORT _Unwind_Reason_Code
@ -132,17 +135,39 @@ _Unwind_Backtrace(_Unwind_Trace_Fn callback, void *ref) {
}
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;
}
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 call personality functions with (_US_VIRTUAL_UNWIND_FRAME |
// _US_FORCE_UNWIND) state.
result = _Unwind_VRS_Interpret(context, unwindInfo, off, len);
if (result != _URC_CONTINUE_UNWIND) {
return _URC_END_OF_STACK;
// 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.
__personality_routine pr = (__personality_routine) readPrel31(unwindInfo);
if (pr(_US_VIRTUAL_UNWIND_FRAME | _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