Re: [PATCH] testsuite/gdb.dwarf2: Fix for dw2-dos-drive failure on ARM

[Omair Javaid <omair dot javaid at linaro dot org>]

On Thu 16 Jan 2014 03:25:34 PM PKT, Pedro Alves wrote:
> On 12/02/2013 09:16 PM, Omair Javaid wrote:
>> On 10/01/2013 08:34 PM, Pedro Alves wrote:
>>> So, in the end, it'd be fine with me to just go in the
>>> direction of your original patch then.  But I think it deserves
>>> a comment:
>>>
>>>  pc_start:
>>>         /* Enough space to fit one instruction.  */
>>> -       .byte   0
>>> +       .4byte  0
>>>  pc_end:
>>>
>>> Could you resend your patch, with that change, a fixed commit
>>> log description and fixed ChangeLog?
>
>> Sorry about responding late to this. I have attached the patch along with commit message and a ChangeLog.
>>
>> Commit Log Message: 
>>
>> 	Avoid test failure due to error thrown from skip prologue code by
>> 	an illegal memory access in case of single byte text section
>
> Period at end of sentences.  That log if very incomplete though.
> See below for what I suggest.  (Note I tweaked the subject too)
>
> The best/easiest is to write that in the git commit log in your
> local tree, and send out the commit exactly as you propose
> to push.
>
>> gdb/testsuite/ChangeLog:
>>
>> 2013-12-02  Omair Javaid  <Omair.Javaid@linaro.org>
>>
>> 	* gdb.dwarf2/dw2-dos-drive.S: Changed text section size to 4 bytes
>
> Period at end of sentence.
>
>>
>> ---
>>  gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S b/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
>> index 682ba4e..f226912 100644
>> --- a/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
>> +++ b/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
>> @@ -15,7 +15,7 @@
>>  
>>  	.text
>>  pc_start:
>> -	.byte	0
>> +	.4byte	0
>
> Still misses comment.  The version below adds one similar to
> what I suggested before.
>
> If this looks good to you, I'll push it.
>
> Thanks.
>
> -- >8 --
> From: Omair Javaid <omair.javaid@linaro.org>
> Subject: Fix testsuite/gdb.dwarf2/dw2-dos-drive.exp on ARM.
>
> This test currently fails on ARM:
>
>   (gdb) PASS: gdb.dwarf2/dw2-dos-drive.exp: set breakpoint pending off
>   break 'z:file.c':func
>   Cannot access memory at address 0x0
>
> The error is GDB trying to read the prologue at the breakpoint's
> address, and failing:
>
>   38 throw_error() exceptions.c:444 0x0016728c
>   37 memory_error() corefile.c:204 0x001d1fcc
>   36 read_memory() corefile.c:223 0x001d201a
>   35 read_memory_unsigned_integer() corefile.c:312 0x001d2166
>   34 arm_skip_prologue() arm-tdep.c:1452 0x00054270
>
>   static CORE_ADDR
>   arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
>   {
>   ...
>     for (skip_pc = pc; skip_pc < limit_pc; skip_pc += 4)
>       {
>         inst = read_memory_unsigned_integer (skip_pc, 4, byte_order_for_code);
>
>
> The test doesn't execute the compiled object's code, so GDB will try
> to read memory from the binary's sections.  Instructions on ARM are
> 4-byte wide, and thus ARM's prologue scanner reads in 4-byte chunks.
> As the section 'func' is put at is only 1 byte long, and no other
> section is allocated contiguously:
>
>   ...
>   Sections:
>   Idx Name          Size      VMA       LMA       File off  Algn
>     0 .text         00000001  00000000  00000000  00000034  2**0
>                     CONTENTS, ALLOC, LOAD, READONLY, CODE
>   ...
>
> ... the exec target fails the read the 4 bytes.
>
> Fix this by increasing the function's size.
>
> gdb/testsuite/ChangeLog:
> 2014-01-16  Omair Javaid  <Omair.Javaid@linaro.org>
>
> 	* gdb.dwarf2/dw2-dos-drive.S: Increase text section size to 4
> 	bytes.
> ---
>  gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S b/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
> index 6e9d360..84006f7 100644
> --- a/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-dos-drive.S
> @@ -15,7 +15,8 @@
>  
>  	.text
>  pc_start:
> -	.byte	0
> +        /* Enough space to fit at least one instruction.  */
> +	.4byte	0
>  pc_end:
>  
>  	.section	.debug_info

Changes look good. Thanks.
Kindly go ahead and push.