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From:   Song Shuai <suagrfillet@gmail.com>
Date:   Wed, 22 Feb 2023 10:13:04 +0000
Message-ID: <CAAYs2=jvYX2L1uGJs3AWsD6UkmbQ0rCHGsgJXw=7z9HcAvgiFQ@mail.gmail.com>
Subject: Re: [PATCH RESEND] scripts/gdb: add lx_current support for riscv
To:     Conor Dooley <conor.dooley@microchip.com>
Cc:     jan.kiszka@siemens.com, kbingham@kernel.org,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, akpm@linux-foundation.org
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Conor Dooley <conor.dooley@microchip.com> =E4=BA=8E2023=E5=B9=B42=E6=9C=882=
2=E6=97=A5=E5=91=A8=E4=B8=89 09:53=E5=86=99=E9=81=93=EF=BC=9A
>
> Hey Song
>
> On Wed, Feb 22, 2023 at 05:37:30PM +0800, Song Shuai wrote:
> > RISC-V uses the tp register to save the current task_struct address
> > as its current() defines. So lx_current() of riscv just returns the
> > dereference of the address cast via task_ptr_type.
>
> FYI, there's already been some patches posted for this:
> https://lore.kernel.org/all/mhng-bdcd75a5-e6d6-4090-8292-a32eb46e4464@pal=
mer-ri-x1c9a/
>
Deepak's patch is much better than mine, which also takes the
userspace and trap handler into count.
So no need to care about this patch.
> That version already has review and ack tags from Palmer and others.
> It seems to me that Andrew is the usual applier of patches for this
> script, so I'm gonna add him to CC here so he is aware - but as it is
> the middle of the merge window the best course of action might just be
> reposting that patch, CCing Andrew, after v6.3-rc1.
>
> Cheers,
> Conor.
>
> >
> > Signed-off-by: Song Shuai <suagrfillet@gmail.com>
> > ---
> >  scripts/gdb/linux/cpus.py | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
> > index 15fc4626d236..6825a9834394 100644
> > --- a/scripts/gdb/linux/cpus.py
> > +++ b/scripts/gdb/linux/cpus.py
> > @@ -173,6 +173,9 @@ def get_current_task(cpu):
> >           else:
> >               raise gdb.GdbError("Sorry, obtaining the current task is =
not allowed "
> >                                  "while running in userspace(EL0)")
> > +    elif utils.is_target_arch("riscv"):
> > +         current_task_addr =3D gdb.parse_and_eval("$tp")
> > +         return current_task_addr.cast(task_ptr_type).dereference()
> >      else:
> >          raise gdb.GdbError("Sorry, obtaining the current task is not y=
et "
> >                             "supported with this arch")
> > --
> > 2.20.1
> >
> >


--=20
Thanks,
Song