On Tue, May 14, 2024 at 5:50 PM Marek Vasut <ma...@denx.de> wrote:
>
> On 5/15/24 2:22 AM, Tim Harvey wrote:
> > If RANDOMIZE_BASE is enabled in the Linux kernel instructing it to
> > randomize the virtual address at which the kernel image is loaded, it
> > expects entropy to be provided by the bootloader by populating
> > /chosen/kaslr-seed with a 64-bit value from source of entropy at boot.
>
> Thanks for working on this one, this is really nice.
>
> > If we have DM_RNG enabled poulate this value automatically when
> > fdt_chosen is called.
Hi Marek,
Just noticed a typo in the commit log - I'll s/poulate/populate/ in v2
> >
> > Signed-off-by: Tim Harvey <thar...@gateworks.com>
> > ---
> > boot/fdt_support.c | 23 +++++++++++++++++++++++
> > 1 file changed, 23 insertions(+)
> >
> > diff --git a/boot/fdt_support.c b/boot/fdt_support.c
> > index 874ca4d6f5af..cd3069baf450 100644
> > --- a/boot/fdt_support.c
> > +++ b/boot/fdt_support.c
> > @@ -7,10 +7,12 @@
> > */
> >
> > #include <abuf.h>
> > +#include <dm.h>
> > #include <env.h>
> > #include <log.h>
> > #include <mapmem.h>
> > #include <net.h>
> > +#include <rng.h>
> > #include <stdio_dev.h>
> > #include <dm/ofnode.h>
> > #include <linux/ctype.h>
> > @@ -300,6 +302,27 @@ int fdt_chosen(void *fdt)
> > if (nodeoffset < 0)
> > return nodeoffset;
> >
> > + if (IS_ENABLED(CONFIG_DM_RNG)) {
> > + struct udevice *dev;
> > + size_t len = 0x8;
> > + u64 *data;
> > +
> > + data = malloc(len);
>
> Can you allocate this 8 byte array on stack , i.e. u64 data[2]; ?
>
Sure... that makes sense - u64 data (just 1 64bit value)
> cmd/kaslrseed.c could use similar clean up (and
> lib/efi_loader/efi_dt_fixup.c and boot/pxe_utils.c ... uhhh). Maybe you
> can deduplicate this functionality into common code shared by all those
> duplicates before the duplication gets out of control ?
>
> lib/kaslrseed.c looks like a good place to put the common stuff.
Yes I started off making a function to do this but then I noticed we
had an fdt_chosen function and it fit there nicer as I didn't have to
find/create the chosen node. I also didn't know of a great place to
put it.
I will create a lib/kaslrseed.c with function for v2.
>
> > + if (!data)
> > + return -ENOMEM;
> > +
> > + err = uclass_get_device(UCLASS_RNG, 0, &dev);
> > + if (!err)
> > + err = dm_rng_read(dev, data, len);
> > + if (!err)
> > + err = fdt_setprop(fdt, nodeoffset, "kaslr-seed",
> > data, len);
> > + if (err < 0) {
> > + printf("WARNING: could not set kaslr-seed %s.\n",
> > + fdt_strerror(err));
> > + return err;
> > + }
>
> You're missing free() here, but it shouldn't be needed if you allocate
> the array on stack, which is better/simpler.
Yes, I will avoid the malloc to fix that.
Thanks,
Tim
