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    SubjectRe: [PATCH v11 2/8] powerpc: Move ima buffer functions to drivers/of/kexec.c
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    On 12/15/20 10:16 AM, Rob Herring wrote:
    > 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@linux.microsoft.com>
    >> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
    >> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
    >> ---
    >> 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.

    Yes.

    >
    >> * 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.
    >
    Ok - will update.

    >> +
    >> + 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.
    >

    setup_ima_buffer() implemented for powerpc can be simplified by using
    fdt_appendprop_addrrange() to add the IMA buffer's address and size to
    "linux,ima-kexec-buffer" node. With that change, setup_ima_buffer() can
    be moved into of_kexec_setup_new_fdt along with all the code in
    powerpc/kexec/ima.c to drivers'of/kexec.c

    I'll make the above change and post the next version shortly.

    thanks,
    -lakshmi


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