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.mauno@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.