Issue #13566 has been updated by wanabe (_ wanabe).


mrkn (Kenta Murata) wrote:
>  r15: 0x00007fff577eb7d0 rip: 0x0000000000000000 rfl: 0x0000000000010246

rb_dump_machine_register() shows "rip: 0x0000000000000000".
And lldb on my environment shows that `uctx->uc_mcontext->__ss.__rip[-2]` is accessed by backtrace() in vm_dump.c. It makes main-thread stop by EXC_BAD_ACCESS.

```
$ lldb -p 936
(lldb) process attach --pid 936
Process 936 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xfffffffffffffffe)
    frame #0: 0x0000000105ccb599 ruby`backtrace(trace=0x0000000105d69cd0, size=<unavailable>) at vm_dump.c:478
   475          unw_set_reg(&cursor, UNW_X86_64_R14, uctx->uc_mcontext->__ss.__r14);
   476          unw_set_reg(&cursor, UNW_X86_64_R15, uctx->uc_mcontext->__ss.__r15);
   477          ip = uctx->uc_mcontext->__ss.__rip;
-> 478          if (((char*)ip)[-2] == 0x0f && ((char*)ip)[-1] == 5) {
   479              /* signal received in syscall */
   480              trace[n++] = (void *)ip;
   481              ip = *(unw_word_t*)uctx->uc_mcontext->__ss.__rsp;

Executable module set to "/Users/wanabe/.rbenv/versions/trunk/bin/ruby".
Architecture set to: x86_64-apple-macosx.
(lldb) 
```

It seems to be related to #12711.

----------------------------------------
Bug #13566: A process freezes at the beginning of C level backtrace when a certain SEGV is occurred
https://bugs.ruby-lang.org/issues/13566#change-64856

* Author: mrkn (Kenta Murata)
* Status: Open
* Priority: Normal
* Assignee: naruse (Yui NARUSE)
* Target version: 
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
I found the issue that a process freezes at the beginning of C level backtrace printing when a certain SEGV is occurred.

I've made a reproducible code in the freeze_on_segv branch of pycall project.
You can check it by the following steps:

```
$ git clone git / github.com:mrkn/pycall.git
$ git checkout -t origin/freeze_on_segv
$ bundle install
$ bin/runner callback.rb
```

When you succeed to reproduce the issue, you can see the following output:

```
$ bin/runner callback.rb
{:rw_refcnt=>1}
42
42
{:res=>42}
{#<FFI::Pointer address=0x00000109057d10>=>[#<Proc:0x007fbb411b93e8 / callback.rb:1>]}
callback.rb:11: [BUG] Segmentation fault at 0x00000000000000
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]

-- Crash Report log information --------------------------------------------
   See Crash Report log file under the one of following:
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.
Don't forget to include the above Crash Report log file in bug reports.

-- Control frame information -----------------------------------------------
c:0005 p:---- s:0021 e:000020 CFUNC  :Py_DecRef
c:0004 p:0105 s:0016 E:002530 TOP    callback.rb:11 [FINISH]
c:0003 p:---- s:0011 e:000010 CFUNC  :load
c:0002 p:0034 s:0006 e:000005 EVAL   bin/runner:6 [FINISH]
c:0001 p:0000 s:0003 E:0013a0 (none) [FINISH]

-- Ruby level backtrace information ----------------------------------------
bin/runner:6:in `<main>'
bin/runner:6:in `load'
callback.rb:11:in `<top (required)>'
callback.rb:11:in `Py_DecRef'

-- Machine register context ------------------------------------------------
 rax: 0x00007fbb43667950 rbx: 0x729546a3ab9700ab rcx: 0x00007fbb40d05190
 rdx: 0x00007fbb40d05190 rdi: 0x0000000109057d10 rsi: 0x00007fbb411e0358
 rbp: 0x00007fff577eb6c0 rsp: 0x00007fff577eb6b8  r8: 0x00007fff577eb6e0
  r9: 0x00000001085e46a1 r10: 0x00007fff577eb610 r11: 0x0000000108ca1d30
 r12: 0x0000000000000000 r13: 0x0000000000000001 r14: 0x729546a3ab9700ab
 r15: 0x00007fff577eb7d0 rip: 0x0000000000000000 rfl: 0x0000000000010246

-- C level backtrace information -------------------------------------------
```

At this point, C-c doesn't work.




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