From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Ard Biesheuvel <ardb@kernel.org>
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 21:26:22 +0000 [thread overview]
Message-ID: <20210113212622.GK1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAMj1kXFBCWgo=vfN35JEcqo_T=kvsWKrffWTaqfjeGjTbDWzJw@mail.gmail.com>
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.
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/
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next prev parent reply other threads:[~2021-01-13 21:31 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 [this message]
2021-01-13 22:43 ` Ard Biesheuvel
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