[llvm-dev] Instruction boundaries

[Muhui Jiang via llvm-dev]

Hi Paulr

I am using the llvm-dwarfdump. This is not the end of the function, thus
there is no 'end_sequence' reported. Here I just want to give you an
exception because you said that all the instructions should be listed
inside dwarf line table. However, I found that it will lost some
instructions. And some instruction's source line is zero.

Besides, I also noticed that inline data is listed inside the line table.

Regards
Muhui

2018-06-26 9:08 GMT-04:00 <paul.robinson at sony.com>:

> There should be a line-table entry for the end of the function, which
> appears to be missing from the dump you provided.  llvm-dwarfdump should
> report this address with 'end_sequence' in the Flags.  Are you using a
> different dumper?
>
>
>
> I am not sure but my guess would be that inline data is not represented in
> the line table.  The line table's primary purpose is to inform the debugger
> about good breakpoint locations, and clearly you do not want to set
> breakpoints in data.  Inline data is probably contained within the code
> ranges described in the DW_TAG_subprogram, however.
>
> --paulr
>
>
>
> *From:* Muhui Jiang [mailto:jiangmuhui at gmail.com]
> *Sent:* Tuesday, June 26, 2018 1:44 AM
> *To:* Robinson, Paul
> *Cc:* Yajin; llvm-dev
> *Subject:* Re: [llvm-dev] Instruction boundaries
>
>
>
> 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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