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 10:26:23 +0800 [thread overview]
Message-ID: <20211208022623.15103-1-mark-pk.tsai@mediatek.com> (raw)
In-Reply-To: <Ya+EUDVYdBvRa7xI@kernel.org>
> 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.
>
> > 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().
>
> > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
> > ---
> > arch/arm/kernel/setup.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> > index 284a80c0b6e1..85ffc9501e38 100644
> > --- a/arch/arm/kernel/setup.c
> > +++ b/arch/arm/kernel/setup.c
> > @@ -851,7 +851,7 @@ static void __init request_standard_resources(const struct machine_desc *mdesc)
> > struct resource *res;
> > u64 i;
> >
> > - kernel_code.start = virt_to_phys(_text);
> > + kernel_code.start = virt_to_phys(_stext);
> > kernel_code.end = virt_to_phys(__init_begin - 1);
> > kernel_data.start = virt_to_phys(_sdata);
> > kernel_data.end = virt_to_phys(_end - 1);
> > --
> > 2.18.0
> >
>
> --
> Sincerely yours,
> Mike.
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next prev parent reply other threads:[~2021-12-08 2:26 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 [this message]
2021-12-08 9:43 ` Mike Rapoport
2021-12-08 10:22 ` Mark-PK Tsai
2021-12-16 15:14 ` Mark-PK Tsai
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