On Tue, Feb 23, 2021 at 08:33:36AM +0200, Niko Mauno wrote:
> On 2/22/21 10:21 PM, Tom Rini wrote:
> > On Mon, Feb 22, 2021 at 07:18:51PM +0000, Niko Mauno wrote:
> >
> > > By declaring board-specific board_fdt_chosen_bootargs() the kernel
> > > command line arguments can be adjusted before injecting to flat dt
> > > chosen node.
> > >
> > > Signed-off-by: Niko Mauno <niko.ma...@vaisala.com>
> > > ---
> > > common/fdt_support.c | 12 +++++++++++-
> > > include/fdt_support.h | 10 ++++++++++
> > > 2 files changed, 21 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/common/fdt_support.c b/common/fdt_support.c
> > > index 08d540bfc8..4379507e30 100644
> > > --- a/common/fdt_support.c
> > > +++ b/common/fdt_support.c
> > > @@ -269,6 +269,15 @@ int fdt_initrd(void *fdt, ulong initrd_start, ulong
> > > initrd_end)
> > > return 0;
> > > }
> > > +/**
> > > + * board_fdt_chosen_bootargs - boards may override this function to use
> > > + * alternative kernel command line arguments
> > > + */
> > > +__weak char *board_fdt_chosen_bootargs(void)
> > > +{
> > > + return env_get("bootargs");
> > > +}
> > > +
> > > int fdt_chosen(void *fdt)
> > > {
> > > int nodeoffset;
> > > @@ -286,7 +295,8 @@ int fdt_chosen(void *fdt)
> > > if (nodeoffset < 0)
> > > return nodeoffset;
> > > - str = env_get("bootargs");
> > > + str = board_fdt_chosen_bootargs();
> > > +
> > > if (str) {
> > > err = fdt_setprop(fdt, nodeoffset, "bootargs", str,
> > > strlen(str) + 1);
> >
> > What's this look like in practice? I'm very wary about changing "set
> > bootargs to what you pass to the kernel" logic that's been there for
> > forever and a constant of every platform. Thanks!
> >
> Hi Tom,
>
> Effectively this change as such should introduce no changes to prevalent
> "bootargs" logic when an overriding board_fdt_chosen_bootargs() is not
> defined. Our motivation for proposing this change is that it provides us
> with a means to introduce an entry point where we can append rootfs specific
> dm-verity kernel command line metrics (such as described in
> https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/verity.html)
> by reading a property from within a kernel tier FIT image header, in order
> to facilitate secure boot process all the way to root filesystem.Right. But what does that logic look like, and why must it be done in C? People have used dm-verity with U-Boot for ages, for example. -- Tom
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