From: Glenn Washburn <development@efficientek.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>,
linux-um <linux-um@lists.infradead.org>,
Richard Weinberger <richard@nod.at>,
Johannes Berg <johannes@sipsolutions.net>,
Anton Ivanov <anton.ivanov@kot-begemot.co.uk>
Subject: Re: [PATCH 2/2] scripts/gdb: Support getting current task struct in UML
Date: Wed, 15 Feb 2023 09:55:29 -0600 [thread overview]
Message-ID: <20230215095529.169f7b0e@crass-HP-ZBook-15-G2> (raw)
In-Reply-To: <31d49cc7-b6a8-8942-016a-9a2793e601c7@siemens.com>
On Wed, 15 Feb 2023 08:45:20 +0100
Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 15.02.23 00:35, Glenn Washburn wrote:
> > A running x86 UML kernel reports with architecture "i386:x86-64" as
> > it is a sub-architecture. However, a difference with bare-metal x86
> > kernels is in how it manages tasks and the current task struct. To
> > identify that the inferior is a UML kernel and not bare-metal, the
> > symbol "uml_kmalloc" is checked for. If it exists, then do the UML
> > specific way of getting the current task struct.
> >
> > Signed-off-by: Glenn Washburn <development@efficientek.com>
> > ---
> > scripts/gdb/linux/cpus.py | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
> > index 289f0bf4d2a1..90908653f6c7 100644
> > --- a/scripts/gdb/linux/cpus.py
> > +++ b/scripts/gdb/linux/cpus.py
> > @@ -163,8 +163,12 @@ def get_current_task(cpu):
> > task_ptr_type = task_type.get_type().pointer()
> >
> > if utils.is_target_arch("x86"):
> > - var_ptr = gdb.parse_and_eval("¤t_task")
> > - return per_cpu(var_ptr, cpu).dereference()
> > + if gdb.lookup_global_symbol("uml_kmalloc"):
> > + var_ptr = gdb.parse_and_eval("(struct task_struct
> > *)cpu_tasks[0].task")
>
> Can't we use an UML indicator that is related to the topic? Why not
> cpu_tasks itself?
Yes, I like that idea, and makes a lot of sense seeing as then we're
sure cpu_tasks exists right before using it. The one thing that I like
about using a symbol with a "uml_" prefix is that it makes it obvious
that this branch is for UML kernels. I ultimately decided against a
comment because using uml_kmalloc seemed self-documenting. Do you think
a comment is warranted if I make the suggested change?
Glenn
> > + return var_ptr.dereference()
> > + else:
> > + var_ptr = gdb.parse_and_eval("¤t_task")
> > + return per_cpu(var_ptr, cpu).dereference()
> > elif utils.is_target_arch("aarch64"):
> > current_task_addr = gdb.parse_and_eval("$SP_EL0")
> > if((current_task_addr >> 63) != 0):
>
> Jan
>
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next prev parent reply other threads:[~2023-02-15 15:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 23:35 [PATCH 0/2] GDB: Support getting current task struct in UML Glenn Washburn
2023-02-14 23:35 ` [PATCH 1/2] scripts/gdb: Correct indentation in get_current_task Glenn Washburn
2023-02-15 7:44 ` Jan Kiszka
2023-02-14 23:35 ` [PATCH 2/2] scripts/gdb: Support getting current task struct in UML Glenn Washburn
2023-02-15 7:45 ` Jan Kiszka
2023-02-15 15:55 ` Glenn Washburn [this message]
2023-02-15 16:04 ` Jan Kiszka
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