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From: Guo Ren <guoren@kernel.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Deepak Gupta <debug@rivosinc.com>,
	palmer@dabbelt.com, linux-kernel@vger.kernel.org,
	 linux-riscv@lists.infradead.org,
	Jisheng Zhang <jszhang@kernel.org>
Subject: Re: [PATCH v2] riscv: VMAP_STACK overflow detection thread-safe
Date: Fri, 28 Jul 2023 20:01:07 +0800	[thread overview]
Message-ID: <CAJF2gTThgCp8-KzghR0cFqDWXxZ2byLtLVF91GdRvBid7U+_aA@mail.gmail.com> (raw)
In-Reply-To: <CABCJKueNhc8qCbZbHJqdCB+PHHy0u5ETP4uWfpWBRaOMX6U6hA@mail.gmail.com>

On Tue, Jul 25, 2023 at 12:34 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> On Thu, Jul 20, 2023 at 8:06 AM Guo Ren <guoren@kernel.org> wrote:
> >
> > On Thu, Jul 20, 2023 at 8:19 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> > >
> > > Are you planning on resending this patch? I see it didn't gain much
> > > traction last time, but this looks like a much cleaner solution for
> > > selecting the overflow stack than having a `shadow_stack` and calling
> > > to C to compute the per-CPU offset. The asm_per_cpu macro also would
> > > come in handy when implementing CONFIG_SHADOW_CALL_STACK, which we'd
> > > like to have on RISC-V too.
> > I remember we ended up with an atomic lock mechanism instead of percpu
> > offset, so what's the benefit of percpu style in overflow_stack path?
>
> The benefit is not needing a separate temporary stack and locks just
Oh, you convinced me it could save another 1KB of memory.

Acked-by: Guo Ren <guoren@kernel.org>

> to compute the per-CPU offset. With CONFIG_SHADOW_CALL_STACK, we would
> also need a "shadow" shadow call stack in this case before calling to
> C code, at which point computing the offsets directly in assembly is
> just significantly cleaner and without concurrency issues.
>
> Sami



-- 
Best Regards
 Guo Ren

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Guo Ren <guoren@kernel.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Deepak Gupta <debug@rivosinc.com>,
	palmer@dabbelt.com, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	Jisheng Zhang <jszhang@kernel.org>
Subject: Re: [PATCH v2] riscv: VMAP_STACK overflow detection thread-safe
Date: Fri, 28 Jul 2023 20:01:07 +0800	[thread overview]
Message-ID: <CAJF2gTThgCp8-KzghR0cFqDWXxZ2byLtLVF91GdRvBid7U+_aA@mail.gmail.com> (raw)
In-Reply-To: <CABCJKueNhc8qCbZbHJqdCB+PHHy0u5ETP4uWfpWBRaOMX6U6hA@mail.gmail.com>

On Tue, Jul 25, 2023 at 12:34 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> On Thu, Jul 20, 2023 at 8:06 AM Guo Ren <guoren@kernel.org> wrote:
> >
> > On Thu, Jul 20, 2023 at 8:19 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> > >
> > > Are you planning on resending this patch? I see it didn't gain much
> > > traction last time, but this looks like a much cleaner solution for
> > > selecting the overflow stack than having a `shadow_stack` and calling
> > > to C to compute the per-CPU offset. The asm_per_cpu macro also would
> > > come in handy when implementing CONFIG_SHADOW_CALL_STACK, which we'd
> > > like to have on RISC-V too.
> > I remember we ended up with an atomic lock mechanism instead of percpu
> > offset, so what's the benefit of percpu style in overflow_stack path?
>
> The benefit is not needing a separate temporary stack and locks just
Oh, you convinced me it could save another 1KB of memory.

Acked-by: Guo Ren <guoren@kernel.org>

> to compute the per-CPU offset. With CONFIG_SHADOW_CALL_STACK, we would
> also need a "shadow" shadow call stack in this case before calling to
> C code, at which point computing the offsets directly in assembly is
> just significantly cleaner and without concurrency issues.
>
> Sami



-- 
Best Regards
 Guo Ren

  reply	other threads:[~2023-07-28 12:01 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-24  9:48 [PATCH v2] riscv: VMAP_STACK overflow detection thread-safe Deepak Gupta
2022-11-24  9:48 ` Deepak Gupta
2022-11-24  9:53 ` Guo Ren
2022-11-24  9:53   ` Guo Ren
2022-11-25 20:13   ` Deepak Gupta
2022-11-25 20:13     ` Deepak Gupta
2022-11-24 15:26 ` Jisheng Zhang
2022-11-24 15:26   ` Jisheng Zhang
2022-11-25 11:29   ` Jisheng Zhang
2022-11-25 11:29     ` Jisheng Zhang
2022-11-25 21:41     ` Deepak Gupta
2022-11-25 21:41       ` Deepak Gupta
2022-11-25 21:35   ` Deepak Gupta
2022-11-25 21:35     ` Deepak Gupta
2023-07-20  0:18 ` Sami Tolvanen
2023-07-20  0:18   ` Sami Tolvanen
2023-07-20 15:06   ` Guo Ren
2023-07-20 15:06     ` Guo Ren
2023-07-24 16:34     ` Sami Tolvanen
2023-07-24 16:34       ` Sami Tolvanen
2023-07-28 12:01       ` Guo Ren [this message]
2023-07-28 12:01         ` Guo Ren
     [not found]   ` <CAKC1njSaR2d-T_UnVJDZYbROT5OLEjBJ+Aps-UHPFTefDc8=6g@mail.gmail.com>
2023-07-20 18:42     ` Deepak Gupta
2023-07-20 18:42       ` Deepak Gupta
2023-07-20 15:10 ` Guo Ren
2023-07-20 15:10   ` Guo Ren
2023-07-24 17:03   ` Sami Tolvanen
2023-07-24 17:03     ` Sami Tolvanen

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