Re: [tcf-dev] Disassembly Service logic with Symbols

[Eugene Tarassov <eugenet@xxxxxxxxxx>]

Hi David,

 

With variable instruction length (e.g. Intel ISA), disassembler must start at a function symbol and stop at the function end.

To avoid garbage output, it will stop at a function boundary regardless how many instructions are requested.

Clients are supposed to request more if needed and merge the data.

 

Regards,

Eugene

 

From: tcf-dev-bounces@xxxxxxxxxxx <tcf-dev-bounces@xxxxxxxxxxx> On Behalf Of Wilson, David
Sent: Monday, August 31, 2020 1:04 AM
To: 'TCF Development' <tcf-dev@xxxxxxxxxxx>
Subject: [tcf-dev] Disassembly Service logic with Symbols

 

CAUTION: This message has originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.

 

Hi All,

 

I am wondering if I could get some clarification on how the disassembly command (in the disassembly service, disassembly.c) is meant to deal with cases when symbols are loaded.

The behavior I have noticed:

 

Command: Disassembly disassemble “ContextID” Addr 1 {}

 

This will return us at least 1 instruction (even though we’ve only specified one byte).

 

Then, we continue to ask for more instructions e.g.:

 

Command: Disassembly disassemble “ContextID” Addr 500 {}

 

And this will return us instructions up to the given size.

 

 

However – we have noticed, with symbols loaded, that this will reach a “limit” on the size of instructions we can ask for (i.e. we reach a point where we cannot ask for more.

 

This means even if we ask for: Command: Disassembly disassemble “ContextID” Addr 1000 {}

 

We still get the same number of instructions returned.

 

 

This happens because of the following block:

 

if (sym_addr_ok && sym_size_ok &&

                    sym_addr <= buf_addr && sym_addr + sym_size > buf_addr &&

                    sym_addr + sym_size <= buf_addr + buf_size) {

                buf_size = sym_addr + sym_size - buf_addr;

                mem_size = (size_t)buf_size;

            }

 

I am wondering if this behavior is expected, and if so – what the purpose of it is.

 

Kind Regards

 

David Wilson

Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Gary Kershaw
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928