[llvm-dev] Instruction boundaries

via llvm-dev llvm-dev at lists.llvm.org
Tue Jun 26 06:08:09 PDT 2018

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.

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


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


<paul.robinson at sony.com<mailto: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).

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org<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


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?


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