Re: [PUSHED gdb-10-branch] arc: Write correct "eret" value during register collection

[Joel Brobecker <brobecker@adacore.com>]

Hello Shahab,

> In collect_register() function of arc-linux-tdep.c, the "eret"
> (exception return) register value was not being reported correctly.
> This patch fixes that.
> 
> Background:
> When asked for the "pc" value, we have to update the "eret" register
> with GDB's STOP_PC.  The "eret" instructs the kernel code where to
> jump back when an instruction has stopped due to a breakpoint.  This
> is how collect_register() was doing so:
> 
> --------------8<--------------
>   if (regnum == gdbarch_pc_regnum (gdbarch))
>     regnum = ARC_ERET_REGNUM;
>   regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
> -------------->8--------------
> 
> Root cause:
> Although this is using the correct offset (ERET register's), it is also
> changing the REGNUM itself.  Therefore, raw_collect (regnum, ...) is
> not reading from "pc" anymore.
> 
> v2:
> - Fix a copy/paste issue as rightfully addressed by Tom [1].
> 
> [1]
> https://sourceware.org/pipermail/gdb-patches/2020-November/173208.html
> 
> gdb/ChangeLog:
> 
> 	* arc-linux-tdep.c (collect_register): Populate "eret" by
> 	"pc" value from the regcache when asked for "pc" value.

Once the first release off a branch is made (GDB 10.1 in this case),
we ask that all changes pushed to the branch for the corrective
release have a PR attached to the change, with details of the problem
being solved.

This is because we use the PRs to create a list of the fixes that
were made in the corrective release, and the PRs are a link to
more information for those who might be interested in them.

Would you mind doing the following please?

  - Create a PR for it? For the description of the problem, I think
    the commit message above is fine. But if you have additional
    information you can share, please do so ;-).

  - Set the PR's target milestone to GDB 10.2.

  - Once you have the PR created, please add a note to the PR
    indicating the commits that were pushed to both master and
    the gdb-10-branch, just keep have an easy track record of
    which commits solved that PR.

    Typically, I would post something like this:

        This PR was solved on master with this commit:

        | commit 10c19fadfd45da5262d2f8b9624be71c274ff15d
        | Author: Shahab Vahedi <shahab@synopsys.com>
        | Date:   Thu Nov 12 12:50:33 2020 +0100
        | Subject: arc: Write correct "eret" value during register collection

        The patch above was also pushed to gdb-10-branch as:

        | commit abaf3df98b69d66c779ff0896d66fea9cbb67481
        | Author: Shahab Vahedi <shahab@synopsys.com>
        | Date:   Thu Nov 12 12:50:33 2020 +0100
        | Subject: arc: Write correct "eret" value during register collection

  - Update the ChangeLog entry on both master and gdb-10-branch
    to include the PR number. E.g.

        | 2020-11-29  Hannes Domani  <ssbssa@yahoo.de>
        |
 !!! -> |     PR tui/26973
        |     * tui/tui-layout.c (tui_apply_current_layout): Don't delete the
        |     static locator win info.

  - Once the above is done, I believe you can close the PR as
    RESOVED/FIXED.

Thank you!

-- 
Joel