[llvm-dev] Instruction boundaries
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
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>>:
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
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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