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);
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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