[Bug tui/30234] New: Can't scroll up in asm view when remote debugging

[Bug tui/30234] New: Can't scroll up in asm view when remote debugging

[hikari at noyu dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=30234

            Bug ID: 30234
           Summary: Can't scroll up in asm view when remote debugging
           Product: gdb
           Version: 13.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tui
          Assignee: unassigned at sourceware dot org
          Reporter: hikari at noyu dot me
  Target Milestone: ---

I'm using GDB to connect to an application that has a primitive implementation
of the GDB Remote Serial Protocol. I'm using GDB 13.1 and the architecture is
set to ARMv6.

If I wait until execution stops at a breakpoint or segfault, and then open the
disassembly view with the `layout asm` command, I get a view that I can scroll
down, but not up. So I can advance past the instruction where the stop
happened, but not backwards.

This only happens when there's no file loaded, and thus no symbols. I suspect
GDB is confused by not having a symbol as a reference point. If I load a file,
even one that apparently only has one symbol (`start`), there's no such
problem.

I can manually reset the view's position using the disass command with a range
of addresses, so it's not as if GDB couldn't disassemble backwards if it wanted
to?

Looking at the packets sent and received, it seems that GDB is not even trying
to read the memory for earlier instructions. No packets seem to be sent or
received when pressing the up arrow key.

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[Bug tui/30234] Can't scroll up in asm view when remote debugging

[luis.machado at arm dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30234

Luis Machado <luis.machado at arm dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |luis.machado at arm dot com
   Last reconfirmed|                            |2023-03-15
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Luis Machado <luis.machado at arm dot com> ---
I can confirm this happens all the way back to gdb-9 when you connect to a
remote target without loading symbols in gdb, for example.

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[Bug tui/30234] Can't scroll up in asm view when remote debugging

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30234

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
Scrolling backward without symbols is hard because gdb doesn't
know where the instructions might start.  I.e., it could pick
some address in the middle of an instruction and produce garbage.
Not an issue on machines with fixed-with instructions, so
maybe gdb could do a little better there, and/or at least
display something informative.

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