From: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
To: <rppt@kernel.org>
Cc: <akpm@linux-foundation.org>, <arnd@arndb.de>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>,
<linux-mediatek@lists.infradead.org>, <linux@armlinux.org.uk>,
<linux@roeck-us.net>, <mark-pk.tsai@mediatek.com>,
<matthias.bgg@gmail.com>, <rmk+kernel@armlinux.org.uk>,
<wangkefeng.wang@huawei.com>, <yj.chiang@mediatek.com>
Subject: Re: [PATCH] arm: remove [_text, _stext) from kernel code resource
Date: Wed, 8 Dec 2021 18:22:37 +0800 [thread overview]
Message-ID: <20211208102237.19706-1-mark-pk.tsai@mediatek.com> (raw)
In-Reply-To: <YbB+O80Th2QI8sTl@kernel.org>
> On Wed, Dec 08, 2021 at 10:26:23AM +0800, Mark-PK Tsai wrote:
> > > On Fri, Dec 03, 2021 at 10:14:16PM +0800, Mark-PK Tsai wrote:
> > > > Remove the [_text, _stext) from Kernel Code.
> > > > Although there are some startup code in head.text, they
> > > > are freed to the buddy system after kernel boot.
> > >
> > > Hmm, I don't see it is being freed anywhere. Can you elaborate when and how
> > > the range [_text, _stext) is freed?
> >
> > arm_memblock_init() reserve [KERNEL_START, KERNEL_END) which are defined as following.
> >
> > #define KERNEL_START _stext
> > #define KERNEL_END _end
> >
> > free_low_memory_core_early() free all the non-reserved range in lowmem,
> > so the range [_text, _stext) is also freed here.
>
> Right, I've misread KERNEL_START as if it was _text...
>
> > >
> > > > And we have memory protection mechanism use this
> > > > which have false alarm when some other IPs doing dma
> > > > if the dma page frame is in the [_text, _stext).
> > > >
> > > > Below are my iomem resource and reserved memory information:
> > > > console:/ # grep Kernel /proc/iomem
> > > > 20208000-219fffff : Kernel code
> > > > 21b00000-21c2e76f : Kernel data
> > > >
> > > > console:/ # cat /sys/kernel/debug/memblock/reserved
> > > > 0: 0x20201000..0x20207fff
> > > > 1: 0x20300000..0x21c2e76f
> > >
> > > What are the addresses of _text and _stext in your configuration?
> >
> > va pa
> > c0008000 20208000 _text
> > c0100000 20300000 _stext
> >
> > >
> > > What these dumps are supposed to show here?
> > >
> >
> > Below is the dump info after applied this patch.
> >
> > console:/ # grep Kernel /proc/iomem
> > 20300000-219fffff : Kernel code
> > 21b00000-21c2e76f : Kernel data
> >
> > console:/ # cat /sys/kernel/debug/memblock/reserved
> > 0: 0x20201000..0x20207fff
> > 1: 0x20300000..0x21c2e76f
> >
> > The difference is that Kernel Code resource match the reserved memblock 1
> > which is reserved in arm_memblock_init().
>
> For that I'd extend the reservation in arm_memblock_init() to include
> [_text, _stext).
>
> Even if the code there is not needed after init, at least we'll keep this
> consistent with other architectures.
>
Extending the reservation in arm_memblock_init() will consume up to SECTION_SIZE
memory for SECTION_SIZE alignment when CONFIG_STRICT_KERNEL_RWX=y.
So we really don't want to extend the reservation because it affect
the low RAM devices.
And arm64_memblock_init() also reserve [_stext, _end) in the recent kernel.
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next prev parent reply other threads:[~2021-12-08 10:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 14:14 [PATCH] arm: remove [_text, _stext) from kernel code resource Mark-PK Tsai
2021-12-07 15:57 ` Mike Rapoport
2021-12-08 2:26 ` Mark-PK Tsai
2021-12-08 9:43 ` Mike Rapoport
2021-12-08 10:22 ` Mark-PK Tsai [this message]
2021-12-16 15:14 ` Mark-PK Tsai
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