OpenWrt – Blame information for rev 1

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1 office 1 From 1dc865b8bbb3911abc8ce53c7ae8a59dc90f6fc3 Mon Sep 17 00:00:00 2001
2 From: Ivan Kold <pixus.ru@gmail.com>
3 Date: Thu, 3 Mar 2016 12:56:30 -0800
4 Subject: [PATCH] Fix throw statement causing memory corruption
5  
6 The __cxxabiv1::__cxa_throw in the GCC's libsupc++ expects
7 sizeof(__cxa_refcounted_exception) bytes be allocated before
8 exception object.
9 uClibc++ allocates only sizeof(__cxa_exception) before an
10 exception object.
11 The __cxxabiv1::__cxa_throw writes in memory before allocated:
12 // gcc-5.2.0/libstdc++-v3/libsupc++/eh_throw.cc:69
13 __cxa_refcounted_exception *header
14 = __get_refcounted_exception_header_from_obj (obj);
15 header->referenceCount = 1;
16  
17 Signed-off-by: Ivan Kold <pixus.ru@gmail.com>
18 ---
19 include/unwind-cxx.h | 34 +++++++++++++++++++++++++++++++++-
20 src/eh_alloc.cpp | 8 ++++----
21 2 files changed, 37 insertions(+), 5 deletions(-)
22  
23 --- a/include/unwind-cxx.h
24 +++ b/include/unwind-cxx.h
25 @@ -1,5 +1,5 @@
26 // -*- C++ -*- Exception handling and frame unwind runtime interface routines.
27 -// Copyright (C) 2001 Free Software Foundation, Inc.
28 +// Copyright (C) 2001-2015 Free Software Foundation, Inc.
29 //
30 // This file is part of GCC.
31 //
32 @@ -13,6 +13,10 @@
33 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
34 // GNU General Public License for more details.
35 //
36 +// Under Section 7 of GPL version 3, you are granted additional
37 +// permissions described in the GCC Runtime Library Exception, version
38 +// 3.1, as published by the Free Software Foundation.
39 +//
40 // You should have received a copy of the GNU General Public License
41 // along with GCC; see the file COPYING. If not, write to
42 // the Free Software Foundation, 59 Temple Place - Suite 330,
43 @@ -40,6 +44,12 @@
44 #include <cstddef>
45 #include "unwind.h"
46  
47 +// Original unwind-cxx.h also includes bits/atomic_word.h which is CPU-specific,
48 +// but always defines _Atomic_word as typedef int .
49 +// Only thing that differs is memory-barrier macroses.
50 +typedef int _Atomic_word;
51 +
52 +
53 #pragma GCC visibility push(default)
54  
55 namespace __cxxabiv1
56 @@ -79,6 +89,13 @@ struct __cxa_exception
57 _Unwind_Exception unwindHeader;
58 };
59  
60 +struct __cxa_refcounted_exception
61 +{
62 + // Manage this header.
63 + _Atomic_word referenceCount;
64 + // __cxa_exception must be last, and no padding can be after it.
65 + __cxa_exception exc;
66 +};
67  
68 // A dependent C++ exception object consists of a header, which is a wrapper
69 // around an unwind object header with additional C++ specific information,
70 @@ -210,6 +227,21 @@ __get_exception_header_from_ue (_Unwind_
71 return reinterpret_cast<__cxa_exception *>(exc + 1) - 1;
72 }
73  
74 +// Acquire the C++ refcounted exception header from the C++ object.
75 +static inline __cxa_refcounted_exception *
76 +__get_refcounted_exception_header_from_obj (void *ptr)
77 +{
78 + return reinterpret_cast<__cxa_refcounted_exception *>(ptr) - 1;
79 +}
80 +
81 +// Acquire the C++ refcounted exception header from the generic exception
82 +// header.
83 +static inline __cxa_refcounted_exception *
84 +__get_refcounted_exception_header_from_ue (_Unwind_Exception *exc)
85 +{
86 + return reinterpret_cast<__cxa_refcounted_exception *>(exc + 1) - 1;
87 +}
88 +
89 } /* namespace __cxxabiv1 */
90  
91 #pragma GCC visibility pop
92 --- a/src/eh_alloc.cpp
93 +++ b/src/eh_alloc.cpp
94 @@ -30,16 +30,16 @@ extern "C" void * __cxa_allocate_excepti
95 void *retval;
96 //The sizeof crap is required by Itanium ABI because we need to provide space for
97 //accounting information which is implementaion (gcc) specified
98 - retval = malloc (thrown_size + sizeof(__cxa_exception));
99 + retval = malloc (thrown_size + sizeof(__cxa_refcounted_exception));
100 if (0 == retval){
101 std::terminate();
102 }
103 - memset (retval, 0, sizeof(__cxa_exception));
104 - return (void *)((unsigned char *)retval + sizeof(__cxa_exception));
105 + memset (retval, 0, sizeof(__cxa_refcounted_exception));
106 + return (void *)((unsigned char *)retval + sizeof(__cxa_refcounted_exception));
107 }
108  
109 extern "C" void __cxa_free_exception(void *vptr) throw(){
110 - free( (char *)(vptr) - sizeof(__cxa_exception) );
111 + free( (char *)(vptr) - sizeof(__cxa_refcounted_exception) );
112 }
113  
114