[llvm-dev] Instruction boundaries

[Muhui Jiang via llvm-dev]

Hi Paulr

According to my observation. Not all the instructions are listed in the
line table.

For example.  We have address 0xa3a0 and 0xa3a4 as the instructions

.text:0000A394                 CMP     R1, #0x42
.text:0000A398                 BHI     loc_AB70
.text:0000A39C                 ADR     R1, off_A3A8
.text:0000A3A0                 LDR     R0, [R1,R0,LSL#2]
.text:0000A3A4                 MOV     PC, R0
.text:0000A3A4 ; ------------------------------
---------------------------------------------
.text:0000A3A8 off_A3A8        DCD loc_AB3C            ; DATA XREF:
main+AC↑o
.text:0000A3AC                 DCD loc_AB34
.text:0000A3B0                 DCD loc_AB70
.text:0000A3B4                 DCD loc_AB70

However, inside the line table. The description is end at 0xa39c. Do you
have any ideas?

  196 0x000000000000a38c    956      7      1   0             0
  197 0x000000000000a39c      0      7      1   0             0

  198 0x000000000000a7d8    959     27      1   0             0  is_stmt
  199 0x000000000000a7f8    959     25      1   0             0
  200 0x000000000000a7fc    961     11      1   0             0  is_stmt
  201 0x000000000000a800    964     15      1   0             0  is_stmt
  202 0x000000000000a808    964     15      1   0             0

Regards
Muhui


2018-06-25 23:31 GMT-04:00 Muhui Jiang <jiangmuhui at gmail.com>:

> Hi paulr
>
> Thanks for your reply. Though DWARF info give me the code address ranges,
> there might be inline data. If so, how to handle this case?
>
> As for the dwarf line table. Sometimes, the source line might be zero. Do
> you know why? If all instructions should be describe in the line table, I
> think analyzing Dwarf line table is enough to get all the instructions
> addresses. Do you agree?
>
> I would also cc my supervisor for the discussion.
>
> Regards
> Muhui
>
> <paul.robinson at sony.com>于2018年6月26日 周二上午2:38写道：
>
>> The main DWARF info should provide the code address ranges for each
>> function, as well as the starting source location.  You could then use the
>> line table to map code ranges to individual source lines.  That could give
>> you a reasonable grasp of the source range for each function.
>>
>> All addresses in the DWARF line table will be instruction addresses.  And
>> in fact, all instructions should be described in the line table (assuming
>> all source was compiled with debug info).
>>
>> --paulr
>>
>>
>>
>> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Muhui
>> Jiang via llvm-dev
>> *Sent:* Monday, June 25, 2018 11:36 AM
>> *To:* llvm-dev
>> *Subject:* [llvm-dev] Instruction boundaries
>>
>>
>>
>> Hi
>>
>>
>>
>> I was wondering whether there are any methods to know what part of the
>> target binary is code.
>>
>>
>>
>> I have some ideas and hope to get your comments.
>>
>>
>>
>> I would like to use LLVM's source level debugging information to extract
>> the source lines belonging to every functions. Then use the dwarf mapping
>> table to transfer the  source level information to binary address. Are
>> there any better methods?
>>
>>
>>
>> Besides, is the address listed inside dwarf line mapping table must be
>> code rather than data?
>>
>>
>>
>> Regards
>>
>> Muhui
>>
>
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