Re: [PATCH] MIPS: Allow compressed images to be loaded at the usual address
Date: Mon Feb 13 2017 - 03:38:08 EST
On Thu, 9 Feb 2017 13:22:37 +0100
Jonas Gorski <jonas.gorski@xxxxxxxxx> wrote:
> On 5 February 2017 at 21:21, Alban <albeu@xxxxxxx> wrote:
> > From: Alban Bedel <albeu@xxxxxxx>
> > Normally compressed images have to be loaded at a different address to
> > allow the decompressor to run. This add an option to let vmlinuz copy
> > itself to the correct address from the normal vmlinux address.
> > Signed-off-by: Alban Bedel <albeu@xxxxxxx>
> > ---
> > arch/mips/Kconfig | 8 ++++++++
> > arch/mips/boot/compressed/head.S | 13 +++++++++++++
> > 2 files changed, 21 insertions(+)
> > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > index b3c5bde..8074fc5 100644
> > --- a/arch/mips/Kconfig
> > +++ b/arch/mips/Kconfig
> > @@ -2961,6 +2961,14 @@ choice
> > bool "Extend builtin kernel arguments with bootloader arguments"
> > endchoice
> > +config ZBOOT_VMLINUZ_AT_VMLINUX_LOAD_ADDRESS
> > + bool "Load compressed images at the same address as uncompressed"
> > + depends on SYS_SUPPORTS_ZBOOT
> > + help
> > + vmlinux and vmlinuz normally have different load addresses, with
> > + this option vmlinuz expect to be loaded at the same address as
> > + vmlinux.
> > +
> > endmenu
> Okay, it took me a while to understand the intention of this change. I
> thought it was for supporting the case that VMLINUZ_LOAD_ADDRESS ==
> VMLINUX_LOAD_ADDRESS, but it is indented for VMLINUZ_LOAD_ADDRESS !=
> VMLINUX_LOAD_ADDRESS, but still being loaded at VMLINUX_LOAD_ADDRESS.
> So I guess that this can only happen with vmlinuz.bin, as vmlinux's
> ELF header will cause it to be loaded at the expected address (for
> sane bootloaders at least).
Yes, this is for bootloaders that use raw images. Having to configure
different load addresses for compressed and uncompressed images was just
> > config LOCKDEP_SUPPORT
> > diff --git a/arch/mips/boot/compressed/head.S b/arch/mips/boot/compressed/head.S
> > index 409cb48..a215171 100644
> > --- a/arch/mips/boot/compressed/head.S
> > +++ b/arch/mips/boot/compressed/head.S
> > @@ -25,6 +25,19 @@ start:
> > move s2, a2
> > move s3, a3
> > +#ifdef CONFIG_ZBOOT_VMLINUZ_AT_VMLINUX_LOAD_ADDRESS
> With a bit of BAL trickery you could easily detect this at runtime and
> then conditionally copy without requiring any additional config
> symbols. Then you aren't limited to being executed from
Could you expand a bit on what you mean with "BAL trickery"? I hoped
that it would be possible to auto detect the current running address,
but as I know very little about MIPS assembly I didn't found how that
could be done.
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