On 23-12-2016 17:46, Sage Weil wrote:
> On Fri, 23 Dec 2016, Willem Jan Withagen wrote:
>> On 23-12-2016 15:26, Sage Weil wrote:
>>> On Fri, 23 Dec 2016, Willem Jan Withagen wrote:
>>>> On 22-12-2016 23:01, Allen Samuels wrote:
>>>>> I believe I mis-read the data. What I've seen before doesn't fit this data.
>>>>>
>>>>> If it fails in unit test, it shouldn't be hard to just set a HW breakpoint on the vptr and see who the culprit is.
>>>>
>>>> Well the _raw class is properly initialised:
>>>> $8 = {_vptr$raw = 0x817578 <vtable for ceph::buffer::raw+16>,
>>>>
>>>> And is "upgraded" to a different class:
>>>> ceph::buffer::raw_combined
>>>>
>>>> But here is the problem...
>>>>
>>>> Hardware watchpoint 5: *0x1054048
>>>>
>>>> Old value = 8484744
>>>> New value = 0
>>>> 0x000000000049ab29 in denc_traits<unsigned long, void>::encode
>>>> (o=@0x10501d0: 123, p=..., f=0) at
>>>> /usr/srcs/Ceph/work/ceph/src/include/denc.h:228
>>>> 228 WRITE_INT_DENC(uint64_t, __le64);
>>>
>>> Ah, okay, this is making a bit more sense now.
>>>
>>> raw_combined is trying to be clever. It has a static create() method to
>>>
>>> - allocate an aligned buffer of size len + sizeof(raw_combined) (with some
>>> rounding up), call it *ptr
>>> - in-place initiailize raw_combined at ptr + len (rounded up), call it *this
>>> - store the the actual data at ptr
>>> - return the raw_combined *this
>>>
>>> It has an overloaded delete operator to free the entire allocate
>>> (roughly this - len) to make this work.
>>>
>>> It sounds a bit like the write into raw_combined's data portion (ptr) is
>>> clobbering vptr. Which probably suggests we wrote too much into the
>>> buffer. Can you print the contents of the raw_combined class and the
>>> appender?
>>
>> Not sure if I understand the values you'd like, but this is a first attempt:
>> (gdb) p p
>> $1 = (ceph::buffer::list::contiguous_appender &) @0x7fffffffd948: {pbl =
>> 0x7fffffffd978, pos = 0x105404f "", bp = {_raw = 0x1054048, _off = 0,
>
> ^^ ^^
>
> Yep, pos is advancing to far and clobbering _raw (the raw_combined).
>
> Try changing that sizeof(T) * 3 to s? I can't tell from the stack
> trace below what path this is.. line 206 on master is
>
> s.push_back("foo");
>
> which is clearly not the code you're running.
'mmm, the version I have is already at '*3'
template<typename T>
void test_denc(T v) {
// estimate
size_t s = 0;
denc(v, s);
ASSERT_NE(s, 0u);
// encode
bufferlist bl;
{
auto a = bl.get_contiguous_appender(sizeof(T) * 3);
denc(v, a);
}
ASSERT_LE(bl.length(), s);
// decode
bl.rebuild();
T out;
auto bpi = bl.front().begin();
denc(out, bpi);
ASSERT_EQ(v, out);
ASSERT_EQ(bpi.get_pos(), bl.c_str() + bl.length());
// test glue
test_encode_decode(v);
}
BTW: I'm off to home. CET = 18:00, and I still have to do my shopping
for the backing pies and deserts for X-mas Eve.
So I'll be on and off-line on irregular basis, as I guess most will be.
Happy hollidays,
--WjW
>
> sage
>
>> _len = 72}, deep = false,
>> out_of_band_offset = 0}
>>
>> I do not know how to get to the raw_combined class
>>
>> But I also found this morning that pos is actually point to 0x105404f
>> after adding 8 bytes of size .
>> So writing any value to that pointer before incrementing will clobber
>> vptr, since it points to 0x1054047.
>>
>> --WjW
>>
>>>
>>> sage
>>>
>>>
>>>>
>>>> The traceback:
>>>> #0 0x000000000049ab29 in denc_traits<unsigned long, void>::encode
>>>> (o=@0x10501d0: 123, p=..., f=0) at
>>>> /usr/srcs/Ceph/work/ceph/src/include/denc.h:228
>>>> #1 0x000000000049a7a8 in denc<unsigned long, denc_traits<unsigned long,
>>>> void> > (o=@0x10501d0: 123, p=..., features=0) at
>>>> /usr/srcs/Ceph/work/ceph/src/include/denc.h:479
>>>> #2 0x000000000049a6a5 in _denc_friend<foo_t const,
>>>> ceph::buffer::list::contiguous_appender> (v=..., p=...) at
>>>> /usr/srcs/Ceph/work/ceph/src/test/test_denc.cc:155
>>>> #3 0x000000000049a62d in foo_t::encode (this=0x10501c8, p=...) at
>>>> /usr/srcs/Ceph/work/ceph/src/test/test_denc.cc:152
>>>> #4 0x000000000049a601 in denc_traits<foo_t, void>::encode (v=...,
>>>> p=..., f=0) at /usr/srcs/Ceph/work/ceph/src/test/test_denc.cc:163
>>>> #5 0x000000000049a188 in denc<foo_t, denc_traits<foo_t, void> > (o=...,
>>>> p=..., features=0) at /usr/srcs/Ceph/work/ceph/src/include/denc.h:479
>>>> #6 0x000000000049a0ac in
>>>> denc_traits<std::__1::map<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >, foo_t,
>>>> std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>,
>>>> std::__1::allocator<char> > >,
>>>> std::__1::allocator<std::__1::pair<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> > const, foo_t> >
>>>>> , void>::encode<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> > > (v=..., p=...)
>>>> at /usr/srcs/Ceph/work/ceph/src/include/denc.h:1010
>>>> #7 0x0000000000494581 in
>>>> denc<std::__1::map<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >, foo_t,
>>>> std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>,
>>>> std::__1::allocator<char> > >,
>>>> std::__1::allocator<std::__1::pair<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> > const, foo_t> >
>>>>> , denc_traits<std::__1::map<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >, foo_t,
>>>> std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>,
>>>> std::__1::allocator<char> > >,
>>>> std::__1::allocator<std::__1::pair<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> > const, foo_t> >
>>>>> , void> > (o=..., p=..., features=0) at
>>>> /usr/srcs/Ceph/work/ceph/src/include/denc.h:479
>>>> #8 0x0000000000490fb1 in
>>>> test_denc<std::__1::map<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> >, foo_t,
>>>> std::__1::less<std::__1::basic_string<char, std::__1::char_traits<char>,
>>>> std::__1::allocator<char> > >,
>>>> std::__1::allocator<std::__1::pair<std::__1::basic_string<char,
>>>> std::__1::char_traits<char>, std::__1::allocator<char> > const, foo_t> >
>>>>>> (v=...) at /usr/srcs/Ceph/work/ceph/src/test/test_denc.cc:49
>>>> #9 0x00000000004904e0 in denc_map_Test::TestBody (this=0x1038030) at
>>>> /usr/srcs/Ceph/work/ceph/src/test/test_denc.cc:206
>>>>
>>>> (gdb) p p
>>>> $10 = (ceph::buffer::list::contiguous_appender &) @0x7fffffffd948: {pbl
>>>> = 0x7fffffffd978, pos = 0x105404f "", bp = {_raw = 0x1054048, _off = 0,
>>>> _len = 72}, deep = false,
>>>> out_of_band_offset = 0}
>>>> (gdb) p *p.bp._raw
>>>> $17 = {_vptr$raw = 0x0, data = 0x1054000 "\003", len = 72, nref = {val =
>>>> 1}, crc_spinlock = 0, crc_map = {__tree_ = {__begin_node_ = 0x1054078,
>>>> __pair1_ =
>>>> {<std::__1::__libcpp_compressed_pair_imp<std::__1::__tree_end_node<std::__1::__tree_node_base<void*>*>,
>>>> std::__1::allocator<std::__1::__tree_node<std::__1::__value_type<std::__1::pair<unsigned
>>>> long, unsigned long>, std::__1::pair<unsigned int, unsigned int> >,
>>>> void*> >, 2>> =
>>>> {<std::__1::allocator<std::__1::__tree_node<std::__1::__value_type<std::__1::pair<unsigned
>>>> long, unsigned long>, std::__1::pair<unsigned int, unsigned int> >,
>>>> void*> >> = {<No data fields>}, __first_ = {
>>>> __left_ = 0x0}}, <No data fields>},
>>>> __pair3_ = {<std::__1::__libcpp_compressed_pair_imp<unsigned long,
>>>> std::__1::__map_value_compare<std::__1::pair<unsigned long, unsigned
>>>> long>, std::__1::__value_type<std::__1::pair<unsigned long, unsigned
>>>> long>, std::__1::pair<unsigned int, unsigned int> >,
>>>> std::__1::less<std::__1::pair<unsigned long, unsigned long> >, true>,
>>>> 2>> = {<std::__1::__map_value_compare<std::__1::pair<unsigned long,
>>>> unsigned long>, std::__1::__value_type<std::__1::pair<unsigned long,
>>>> unsigned long>, std::__1::pair<unsigned int, unsigned int> >,
>>>> std::__1::less<std::__1::pair<unsigned long, unsigned long> >, true>> =
>>>> {<std::__1::less<std::__1::pair<unsigned long, unsigned long> >> =
>>>> {<std::__1::binary_function<std::__1::pair<unsigned long, unsigned
>>>> long>, std::__1::pair<unsigned long, unsigned long>, bool>> = {<No data
>>>> fields>}, <No data fields>}, <No data fields>},
>>>> __first_ = 0}, <No data fields>}}}}
>>>>
>>>> (gdb) disassemble
>>>> Dump of assembler code for function denc_traits<unsigned long,
>>>> void>::encode(unsigned long const&,
>>>> ceph::buffer::list::contiguous_appender&, unsigned long):
>>>> 0x000000000049aaf0 <+0>: push %rbp
>>>> 0x000000000049aaf1 <+1>: mov %rsp,%rbp
>>>> 0x000000000049aaf4 <+4>: sub $0x20,%rsp
>>>> 0x000000000049aaf8 <+8>: mov $0x8,%eax
>>>> 0x000000000049aafd <+13>: mov %eax,%ecx
>>>> 0x000000000049aaff <+15>: mov %rdi,-0x8(%rbp)
>>>> 0x000000000049ab03 <+19>: mov %rsi,-0x10(%rbp)
>>>> 0x000000000049ab07 <+23>: mov %rdx,-0x18(%rbp)
>>>> 0x000000000049ab0b <+27>: mov -0x8(%rbp),%rdx
>>>> 0x000000000049ab0f <+31>: mov (%rdx),%rdx
>>>> 0x000000000049ab12 <+34>: mov -0x10(%rbp),%rdi
>>>> 0x000000000049ab16 <+38>: mov %rcx,%rsi
>>>> 0x000000000049ab19 <+41>: mov %rdx,-0x20(%rbp)
>>>> 0x000000000049ab1d <+45>: callq 0x49a1d0
>>>> <ceph::buffer::list::contiguous_appender::get_pos_add(unsigned long)>
>>>> 0x000000000049ab22 <+50>: mov -0x20(%rbp),%rcx
>>>> 0x000000000049ab26 <+54>: mov %rcx,(%rax)
>>>> => 0x000000000049ab29 <+57>: add $0x20,%rsp
>>>> 0x000000000049ab2d <+61>: pop %rbp
>>>> 0x000000000049ab2e <+62>: retq
>>>> End of assembler dump.
>>>>
>>>> (gdb) info registers
>>>> rax 0x1054047 17121351
>>>> rbx 0x0 0
>>>> rcx 0x7b 123
>>>> rdx 0x7b 123
>>>> rsi 0x7fffffffd948 140737488345416
>>>> rdi 0x105404f 17121359
>>>> rbp 0x7fffffffd4f0 0x7fffffffd4f0
>>>> rsp 0x7fffffffd4d0 0x7fffffffd4d0
>>>> r8 0x0 0
>>>> r9 0x0 0
>>>> r10 0x0 0
>>>> r11 0x829100 8556800
>>>> r12 0x7fffffffe910 140737488349456
>>>> r13 0x7fffffffe928 140737488349480
>>>> r14 0x7fffffffe918 140737488349464
>>>> r15 0x1 1
>>>> rip 0x49ab29 0x49ab29 <denc_traits<unsigned long,
>>>> void>::encode(unsigned long const&,
>>>> ceph::buffer::list::contiguous_appender&, unsigned long)+57>
>>>>
>>>> And this is wierd:
>>>> %rax contains 0x1054047
>>>> _raw is 0x1054048
>>>>
>>>> So writing %rcx to (%rax) is definitly going to overwrite the larger
>>>> part of _raw.
>>>>
>>>> So now the question transforms into:
>>>> Why does %rax hold this wierd value ??
>>>> or Why does get_pos_add(sizeof(etype)) a negative offset ??
>>>>
>>>> Got to go and do real dayjob work.
>>>>
>>>> --WjW
>>>> --
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>>>>
>>
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