linux-kernel - Re: [PATCH RESEND] scripts/gdb: add lx

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Date:   Wed, 22 Feb 2023 09:52:27 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Song Shuai <suagrfillet@...il.com>
CC:     <jan.kiszka@...mens.com>, <kbingham@...nel.org>,
        <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <linux-kernel@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <akpm@...ux-foundation.org>
Subject: Re: [PATCH RESEND] scripts/gdb: add lx_current support for riscv

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@palmer-ri-x1c9a/

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@...il.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 = 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 yet "
>                             "supported with this arch")
> -- 
> 2.20.1
> 
> 

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