Re: [Patch] Fix windows 64 unwinding issues

[Tristan Gingold <gingold at adacore dot com>]

> On 18 Mar 2015, at 10:21, Pedro Alves <palves@redhat.com> wrote:
> 
> Hi Tristan,
> 
> Looks good to me.  Thanks for the investigations and adding
> comments.
> 
> Please fix the nits below and push.

Thanks for the review.  Just pushed with the nits fixed.

Tristan.

> 
> On 03/05/2015 01:42 PM, Tristan Gingold wrote:
> 
>> 
>> commit da3b5213dc072fca195451a04f35a2eb6342bb62
>> Author: Tristan Gingold <gingold@adacore.com>
>> Date:   Thu Mar 5 14:36:32 2015 +0100
>> 
>>    Fix amd64 windows unwinding issues within MS dlls.
>> 
>>    Unwind info in system dlls uses almost all possible codes, contrary to unwind
>>    info generated by gcc.  A few issues have been discovered: incorrect handling
>>    of SAVE_NONVOL opcodes and incorrect in prologue range checks.  Furthermore I
>>    added comments not to forget what has been investigated.
>> 
>>    gdb/ChangeLog:
>>    	* amd64-windows-tdep.c (amd64_windows_find_unwind_info): Move
>>    	redirection code to ...
>>    	(amd64_windows_frame_decode_insns): ... Here.  Fix in prologue
>>    	checks.  Fix SAVE_NONVOL operations.  Add debug code and comments.
>> 
>> diff --git a/gdb/amd64-windows-tdep.c b/gdb/amd64-windows-tdep.c
>> index 2aa10a1..9278a26 100644
>> --- a/gdb/amd64-windows-tdep.c
>> +++ b/gdb/amd64-windows-tdep.c
>> @@ -621,9 +621,47 @@ amd64_windows_frame_decode_insns (struct frame_info *this_frame,
>>   CORE_ADDR cur_sp = cache->sp;
>>   struct gdbarch *gdbarch = get_frame_arch (this_frame);
>>   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
>> -  int j;
>> +  int first = 1;
>> +
>> +  /* There are at least 3 possibilities to share an unwind info entry:
>> +     1. Two different runtime_function entries (in .pdata) can point to the
>> +        same unwind info entry.  There is no such indication while unwinding,
>> +	so we don't really care about that case.  We suppose this scheme is
>> +	used to save memory when the unwind entries are exactly the same.
> 
> tabs/spaces here don't look right.
> 
>> +     2. Chained unwind_info entries, with no unwind codes (no prologue).
>> +        There is a major difference with the previous case: the pc range for
>> +	the function is different (in case 1, the pc range comes from the
>> +	runtime_function entry; in case 2, the pc range for the chained entry
>> +	comes from the first unwind entry).  Case 1 cannot be used instead as
> 
> Likewise.
> 
>> +	the pc is not in the prologue.  This case is officially documented.
>> +	(There might be unwind code in the first unwind entry to handle
>> +	additionnal unwinding).  GCC (at least until gcc 5.0) doesn't chain
> 
> Typo "additionnal".
> 
>> +	entries.
>> +     3. Undocumented unwind info redirection.  Hard to know the exact purpose,
>> +        so it is considered as a memory optimization of case 2.
>> +  */
>> 
>> -  for (j = 0; ; j++)
>> +  if (unwind_info & 1)
>> +    {
>> +      /* Unofficially documented unwind info redirection, when UNWIND_INFO
>> +	 address is odd (http://www.codemachine.com/article_x64deepdive.html).
>> +      */
>> +      struct external_pex64_runtime_function d;
>> +      CORE_ADDR sa, ea;
>> +
>> +      if (target_read_memory (cache->image_base + (unwind_info & ~1),
>> +			      (gdb_byte *) &d, sizeof (d)) != 0)
>> +	return;
>> +
>> +      cache->start_rva =
>> +	extract_unsigned_integer (d.rva_BeginAddress, 4, byte_order);
> 
> "=" goes on the next line.
> 
>> +      cache->end_rva =
>> +	extract_unsigned_integer (d.rva_EndAddress, 4, byte_order);
>> +      unwind_info =
>> +	extract_unsigned_integer (d.rva_UnwindData, 4, byte_order);
>> +    }
> 
> Thanks,
> Pedro Alves
>