Re: [PATCH v12] ARM: uncompress: Validate start of physical memory against passed DTB

[Geert Uytterhoeven]

Hi Marek,

On Thu, Jan 7, 2021 at 11:36 AM Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
> On 04.01.2021 14:01, Geert Uytterhoeven wrote:
> > Currently, the start address of physical memory is obtained by masking
> > the program counter with a fixed mask of 0xf8000000.  This mask value
> > was chosen as a balance between the requirements of different platforms.
> > However, this does require that the start address of physical memory is
> > a multiple of 128 MiB, precluding booting Linux on platforms where this
> > requirement is not fulfilled.
> >
> > Fix this limitation by validating the masked address against the memory
> > information in the passed DTB.  Only use the start address
> > from DTB when masking would yield an out-of-range address, prefer the
> > traditional method in all other cases.  Note that this applies only to the
> > explicitly passed DTB on modern systems, and not to a DTB appended to
> > the kernel, or to ATAGS.  The appended DTB may need to be augmented by
> > information from ATAGS, which may need to rely on knowledge of the start
> > address of physical memory itself.
> >
> > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM
> > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space),
> > i.e. not at a multiple of 128 MiB.
> >
> > Suggested-by: Nicolas Pitre <nico@xxxxxxxxxxx>
> > Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > Acked-by: Nicolas Pitre <nico@xxxxxxxxxxx>
>
> I've checked all of my arm 32bit test systems and they still boot fine
> with this patch. Feel free to add my:
>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> although I didn't test exactly the new features added by it.

Thank you, regression-testing is very valuable!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds