From: Ard Biesheuvel <ardb@kernel.org>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Alexander Sverdlin <alexander.sverdlin@nokia.com>,
Arnd Bergmann <arnd@arndb.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/2] ARM: axxia: remove TEXT_OFFSET override hack
Date: Wed, 13 Jan 2021 23:43:34 +0100 [thread overview]
Message-ID: <CAMj1kXHDztciyOMuh85Mewy6BJm5i3JT3hKyAtuudbBKB+As8g@mail.gmail.com> (raw)
In-Reply-To: <20210113212622.GK1551@shell.armlinux.org.uk>
On Wed, 13 Jan 2021 at 22:26, Russell King - ARM Linux admin
<linux@armlinux.org.uk> wrote:
>
> On Wed, Jan 13, 2021 at 06:49:17PM +0100, Ard Biesheuvel wrote:
> > If you are going to fix the bootloader, better to let it relocate
> > itself to the top of DRAM as is usually done.
> >
> > The boot requirements [0] state that the uncompressed image must be
> > placed TEXT_OFFSET - PAGE_OFFSET bytes from the start of system
>
> No, that is incorrect on several counts.
>
Nevertheless, it is literally what booting.rst claims:
"""
When booting a raw (non-zImage) kernel the constraints are tighter.
In this case the kernel must be loaded at an offset into system equal
to TEXT_OFFSET - PAGE_OFFSET.
"""
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/booting.rst#n180
so we might want to fix that.
> 1. PAGE_OFFSET is the virtual address offset of the start of RAM as
> seen by the kernel; the boot loader has no knowledge of this. You
> mean essentially what the kernel calls PHYS_OFFSET.
>
> 2. TEXT_OFFSET is the offset from the start of RAM to the kernel image
> both in terms of what the kernel calls PAGE_OFFSET and PHYS_OFFSET.
>
> Essentially, the page mapped at PAGE_OFFSET in the kernel's virtual
> address space is the physical page at PHYS_OFFSET when the MMU is off.
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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prev parent reply other threads:[~2021-01-13 22:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 10:30 [PATCH 0/2] ARM: remove TEXT_OFFSET override for Axxia Ard Biesheuvel
2021-01-11 10:30 ` [PATCH 1/2] ARM: take memreserve FDT entries into account when discovering base of RAM Ard Biesheuvel
2021-01-11 10:30 ` [PATCH 2/2] ARM: axxia: remove TEXT_OFFSET override hack Ard Biesheuvel
2021-01-12 10:34 ` Alexander Sverdlin
2021-01-12 10:40 ` Ard Biesheuvel
2021-01-12 11:22 ` Alexander Sverdlin
2021-01-12 13:55 ` Alexander Sverdlin
2021-01-12 14:05 ` Ard Biesheuvel
2021-01-12 14:21 ` Alexander Sverdlin
2021-01-13 17:49 ` Ard Biesheuvel
2021-01-13 21:26 ` Russell King - ARM Linux admin
2021-01-13 22:43 ` Ard Biesheuvel [this message]
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