On Mon, Dec 14, 2020 at 11:18:48AM -0800, Lakshmi Ramasubramanian wrote:
> The functions do_get_kexec_buffer() and get_addr_size_cells(),
> defined in arch/powerpc/kexec/ima.c, retrieve the address and size
> of the given property from the device tree blob. These functions do
> not have architecture specific code, but are currently limited to
> powerpc. do_get_kexec_buffer() correctly handles a device tree property
> that is a child node of the root node, but not anything other than
> the immediate root child nodes.
>
> Move architecture independent functions get_ima_kexec_buffer() and
> get_root_addr_size_cells() to "drivers/of/kexec.c". These functions
> retrieve the chosen node "linux,ima-kexec-buffer" from the device tree,
> and return the address and size of the buffer used for carrying forward
> the IMA measurement log across kexec system call.
>
> Co-developed-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/of/kexec.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/of.h | 3 ++
> 2 files changed, 71 insertions(+)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 66787be081fe..9af5371340b1 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -30,6 +30,10 @@
> /**
> * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
> *
> + * @fdt: Flattened Device Tree to update
> + * @start: Starting address of the reservation to delete
> + * @size: Size of the reservation to delete
> + *
This belongs in the patch adding fdt_find_and_del_mem_rsv.
> * Return: 0 on success, or negative errno on error.
> */
> static int fdt_find_and_del_mem_rsv(void *fdt, unsigned long start, unsigned long size)
> @@ -226,3 +230,67 @@ int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
>
> return 0;
> }
> +
> +/**
> + * get_root_addr_size_cells - Get address and size of root node
> + *
> + * @addr_cells: Return address of the root node
> + * @size_cells: Return size of the root node
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int get_root_addr_size_cells(int *addr_cells, int *size_cells)
> +{
> + struct device_node *root;
> +
> + root = of_find_node_by_path("/");
> + if (!root)
> + return -EINVAL;
> +
> + *addr_cells = of_n_addr_cells(root);
> + *size_cells = of_n_size_cells(root);
> +
> + of_node_put(root);
> +
> + return 0;
> +}
> +
> +/**
> + * get_ima_kexec_buffer - Get address and size of IMA kexec buffer
> + *
> + * @fdt: Flattened Device Tree
> + * @chosen_node: Offset of chosen node in the FDT
> + * @addr: Return address of the node
> + * @size: Return size of the node
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int get_ima_kexec_buffer(void *fdt, int chosen_node,
> + unsigned long *addr, size_t *size)
> +{
> + const void *prop;
> + int addr_cells, size_cells, prop_len;
> + int rc;
> +
> + rc = get_root_addr_size_cells(&addr_cells, &size_cells);
> + if (rc)
> + return rc;
> +
> + if (fdt)
> + prop = fdt_getprop(fdt, chosen_node,
> + "linux,ima-kexec-buffer", &prop_len);
> + else
> + prop = of_get_property(of_chosen,
> + "linux,ima-kexec-buffer", &prop_len);
This is an odd structure. The DT APIs are generally of_foo() for
unflattened tree and of_flat_foo() for FDT.
> +
> + if (!prop)
> + return -ENOENT;
> +
> + if (prop_len < 4 * (addr_cells + size_cells))
> + return -EINVAL;
> +
> + *addr = of_read_number(prop, addr_cells);
> + *size = of_read_number(prop + 4 * addr_cells, size_cells);
> +
> + return 0;
> +}
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 3375f5295875..fb2ef274135d 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -562,6 +562,9 @@ struct kimage;
> int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
> unsigned long initrd_load_addr, unsigned long initrd_len,
> const char *cmdline);
> +int get_root_addr_size_cells(int *addr_cells, int *size_cells);
> +int get_ima_kexec_buffer(void *fdt, int chosen_node,
> + unsigned long *addr, size_t *size);
The whole point of moving code out of arch code was to avoid all these
cross tree calls.
I was expecting the next step to be moving setup_ima_buffer() call into
of_kexec_setup_new_fdt with all the code in powerpc/kexec/ima.c moved
here. Then the end result to enable on arm64 is just selecting
HAVE_IMA_KEXEC and adding fields to kimage_arch.
Rob
