From: Arnd Bergmann <arnd@arndb.de>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Gregory CLEMENT <gregory.clement@bootlin.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 1/6] ARM: Use PAGE_SIZE for ELF_EXEC_PAGESIZE
Date: Fri, 12 Jun 2020 10:46:17 +0200 [thread overview]
Message-ID: <CAK8P3a2BpNVSE86zEYSGd7x+OF-7spjGmU331TbQX=DRAkpMoQ@mail.gmail.com> (raw)
In-Reply-To: <20200612083510.GB1551@shell.armlinux.org.uk>
On Fri, Jun 12, 2020 at 10:35 AM Russell King - ARM Linux admin
<linux@armlinux.org.uk> wrote:
> On Fri, Jun 12, 2020 at 10:22:17AM +0200, Arnd Bergmann wrote:
> > On Thu, Jun 11, 2020 at 3:49 PM Gregory CLEMENT
> > <gregory.clement@bootlin.com> wrote:
> > >
> > > Currently ELF_EXEC_PAGESIZE is 4096 which is also the page size. In
> > > order to be able to use other size of page than 4K, use PAGE_SIZE
> > > instead of the hardcoded value.
> > >
> > > The use of PAGE_SIZE will be also aligned with what we find in other
> > > architectures such as arm64.
> > >
> > > This is inspired from fa0ca2726ea9 ("DSMP 64K support") and
> > > 4ef803e12baf ("mmu: large-page: Added support for multiple kernel page
> > > sizes") from
> > > https://github.com/MarvellEmbeddedProcessors/linux-marvell.git
> > >
> > > Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
> >
> > IIRC using page sizes above 16KB here also requires using a
> > non-ancient linker in user space that places sections on
> > ELF_EXEC_PAGESIZE boundaries, right?
Correction: I was thinking of SHMLBA, not ELF_EXEC_PAGESIZE.
SHMLBA is defined to 16KB in arch/arm/ at the moment (based on 4K
page size), or (4 * PAGE_SIZE) on arm64, which can blow up to 256KB.
AFAICT, SHMLBA should now be defined as "min(16384, PAGE_SIZE)".
> Doesn't that mean that this change breaks all existing userspace when
> ELF_EXEC_PAGESIZE is not 4k?
I think a lot of older user space would be broken with page sizes larger
than 16KB, but would still work with 8KB or 16KB. Larger page sizes
would only work with user space that was linked in the last five years
or so, using a toolchain that has the workarounds for running on arm64
with 64KB page size.
Arnd
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next prev parent reply other threads:[~2020-06-12 8:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 13:49 [PATCH v2 0/6] ARM: Add support for large kernel page (from 8K to 64K) Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 1/6] ARM: Use PAGE_SIZE for ELF_EXEC_PAGESIZE Gregory CLEMENT
2020-06-12 8:22 ` Arnd Bergmann
2020-06-12 8:35 ` Russell King - ARM Linux admin
2020-06-12 8:46 ` Arnd Bergmann [this message]
2020-06-12 8:50 ` Russell King - ARM Linux admin
2020-06-12 11:50 ` Catalin Marinas
2020-06-12 12:06 ` Gregory CLEMENT
2020-06-12 8:52 ` Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 2/6] ARM: pagetable: prepare hardware page table to use large page Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 3/6] ARM: Make the number of fix bitmap depend on the page size Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 4/6] ARM: mm: Aligned pte allocation to one page Gregory CLEMENT
2020-06-12 8:37 ` Arnd Bergmann
2020-06-12 10:25 ` Catalin Marinas
2020-06-12 11:56 ` Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 5/6] ARM: Add large kernel page support Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 6/6] ARM: Add 64K page support at MMU level Gregory CLEMENT
2020-06-11 16:21 ` [PATCH v2 0/6] ARM: Add support for large kernel page (from 8K to 64K) Russell King - ARM Linux admin
2020-06-12 9:15 ` Gregory CLEMENT
2020-06-12 9:23 ` Arnd Bergmann
2020-06-12 12:21 ` Catalin Marinas
2020-06-12 12:49 ` Arnd Bergmann
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