Re: [kvm-unit-tests PATCH] lib/devicetree: Support 64 bit addresses for the initrd

Alexandru Elisei
2022-02-14T14:05:54Z

Hi Drew,

On Mon, Feb 14, 2022 at 02:52:26PM +0100, Andrew Jones wrote:
> On Mon, Feb 14, 2022 at 12:05:06PM +0000, Alexandru Elisei wrote:
> > The "linux,initrd-start" and "linux,initrd-end" properties encode the start
> > and end address of the initrd. The size of the address is encoded in the
> > root node #address-cells property and can be 1 cell (32 bits) or 2 cells
> > (64 bits). Add support for parsing a 64 bit address.
> >
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> > ---
> > lib/devicetree.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/devicetree.c b/lib/devicetree.c
> > index 409d18bedbba..7cf64309a912 100644
> > --- a/lib/devicetree.c
> > +++ b/lib/devicetree.c
> > @@ -288,7 +288,7 @@ int dt_get_default_console_node(void)
> > int dt_get_initrd(const char **initrd, u32 *size)
> > {
> > const struct fdt_property *prop;
> > - const char *start, *end;
> > + u64 start, end;
> > int node, len;
> > u32 *data;
> >
> > @@ -303,7 +303,11 @@ int dt_get_initrd(const char **initrd, u32 *size)
> > if (!prop)
> > return len;
> > data = (u32 *)prop->data;
> > - start = (const char *)(unsigned long)fdt32_to_cpu(*data);
> > + start = fdt32_to_cpu(*data);
> > + if (len == 8) {
> > + data++;
> > + start = (start << 32) | fdt32_to_cpu(*data);
> > + }
> >
> > prop = fdt_get_property(fdt, node, "linux,initrd-end", &len);
> > if (!prop) {
> > @@ -311,10 +315,14 @@ int dt_get_initrd(const char **initrd, u32 *size)
> > return len;
> > }
> > data = (u32 *)prop->data;
> > - end = (const char *)(unsigned long)fdt32_to_cpu(*data);
> > + end = fdt32_to_cpu(*data);
> > + if (len == 8) {
> > + data++;
> > + end = (end << 32) | fdt32_to_cpu(*data);
> > + }
> >
> > - *initrd = start;
> > - *size = (unsigned long)end - (unsigned long)start;
> > + *initrd = (char *)start;
> > + *size = end - start;
> >
> > return 0;
> > }
> > --
> > 2.35.1
> >
>
> I added this patch on

Thanks for the quick reply!

>
> diff --git a/lib/devicetree.c b/lib/devicetree.c
> index 7cf64309a912..fa8399a7513d 100644
> --- a/lib/devicetree.c
> +++ b/lib/devicetree.c
> @@ -305,6 +305,7 @@ int dt_get_initrd(const char **initrd, u32 *size)
> data = (u32 *)prop->data;
> start = fdt32_to_cpu(*data);
> if (len == 8) {
> + assert(sizeof(long) == 8);

I'm sketchy about arm with LPAE, but wouldn't it be legal to have here a 64
bit address, even if the architecture is 32 bits? Or was the assert added
more because kvm-unit-tests doesn't support LPAE on arm?

> data++;
> start = (start << 32) | fdt32_to_cpu(*data);
> }
> @@ -321,7 +322,7 @@ int dt_get_initrd(const char **initrd, u32 *size)
> end = (end << 32) | fdt32_to_cpu(*data);
> }
>
> - *initrd = (char *)start;
> + *initrd = (char *)(unsigned long)start;

My bad here, I forgot to test on arm. Tested your fix and the compilation
error goes away.

Thanks,
Alex

> *size = end - start;
>
> return 0;
>
>
> To fix compilation on 32-bit arm.
>
>
> And now merged through misc/queue.
>
> Thanks,
> drew
>