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SubjectRe: [RFC][PATCH 1/1] Carry ima measurement log for arm64 via kexec_file_load
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Hello Prakhar,

Answering this part from the cover letter:

> The code is in most part same as powerpc, i want to get feedback as to
> how/correct way to refactor the code so that cross architecture
> partial helpers can be put in a common place.

That's a great idea. If it could go to drivers/of/ as Stephen Boyd
mentioned in the other email that would be great.

More comments below.

Prakhar Srivastava <prsriva@linux.microsoft.com> writes:

> Carry ima measurement log for arm64 via kexec_file_load.
> add support to kexec_file_load to pass the ima measurement log
>
> This patch adds entry for the ima measurement log in the
> dtb which is then used in the kexec'ed session to fetch the
> segment and then load the ima measurement log.
>
> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
> ---
> arch/arm64/Kconfig | 7 +
> arch/arm64/include/asm/ima.h | 31 ++++
> arch/arm64/include/asm/kexec.h | 4 +
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/ima_kexec.c | 219 +++++++++++++++++++++++++
> arch/arm64/kernel/machine_kexec_file.c | 39 +++++
> 6 files changed, 301 insertions(+)
> create mode 100644 arch/arm64/include/asm/ima.h
> create mode 100644 arch/arm64/kernel/ima_kexec.c
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 3adcec05b1f6..9e1b831e7baa 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -964,6 +964,13 @@ config KEXEC_FILE
> for kernel and initramfs as opposed to list of segments as
> accepted by previous system call.
>
> +config HAVE_IMA_KEXEC
> + bool "enable arch specific ima buffer pass"
> + depends on KEXEC_FILE
> + help
> + This adds support to carry ima log to the next kernel in case
> + of kexec_file_load
> +
> config KEXEC_VERIFY_SIG
> bool "Verify kernel signature during kexec_file_load() syscall"
> depends on KEXEC_FILE

This Kconfig should be defined in arch/Kconfig so that both arm64 and
powerpc can select it.

> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 478491f07b4f..9620f90bd0e1 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
> obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
> obj-$(CONFIG_ARM64_SSBD) += ssbd.o
> obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
> +obj-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>
> obj-y += vdso/ probes/
> obj-$(CONFIG_COMPAT_VDSO) += vdso32/
> diff --git a/arch/arm64/kernel/ima_kexec.c b/arch/arm64/kernel/ima_kexec.c
> new file mode 100644
> index 000000000000..5ae0d776ec42
> --- /dev/null
> +++ b/arch/arm64/kernel/ima_kexec.c
> @@ -0,0 +1,219 @@
> +/*
> + * Copyright (C) 2016 IBM Corporation
> + *
> + * Authors:
> + * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */

The powerpc file was updated to use the SPDX tag and remove the
paragraph above. Please update your file to match.

> +#include <linux/slab.h>
> +#include <linux/kexec.h>
> +#include <linux/of.h>
> +#include <linux/memblock.h>
> +#include <linux/libfdt.h>
> +#include <asm/kexec.h>
> +#include <asm/ima.h>
> +
> +static int get_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;
> +}
> +
> +static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
> + size_t *size)
> +{
> +

This spurious blank line only exists in the arm64 version. Should be
removed.

> + int ret, addr_cells, size_cells;
> +
> + ret = get_addr_size_cells(&addr_cells, &size_cells);
> + if (ret)
> + return ret;
> +
> + if (len < 4 * (addr_cells + size_cells))
> + return -ENOENT;
> +
> + *addr = of_read_number(prop, addr_cells);
> + *size = of_read_number(prop + 4 * addr_cells, size_cells);
> +
> + return 0;
> +}
> +
> +/**
> + * ima_get_kexec_buffer - get IMA buffer from the previous kernel
> + * @addr: On successful return, set to point to the buffer contents.
> + * @size: On successful return, set to the buffer size.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +int ima_get_kexec_buffer(void **addr, size_t *size)
> +{
> + int ret, len;
> + unsigned long tmp_addr;
> + size_t tmp_size;
> + const void *prop;
> +
> + prop = of_get_property(of_chosen, FDT_PROP_KEXEC_BUFFER, &len);
> + if (!prop)
> + return -ENOENT;
> +
> + ret = do_get_kexec_buffer(prop, len, &tmp_addr, &tmp_size);
> + if (ret)
> + return ret;
> +
> + *addr = __va(tmp_addr);
> + *size = tmp_size;
> + return 0;
> +}
> +
> +/**
> + * ima_free_kexec_buffer - free memory used by the IMA buffer
> + */
> +int ima_free_kexec_buffer(void)
> +{
> + int ret;
> + unsigned long addr;
> + size_t size;
> + struct property *prop;
> +
> + prop = of_find_property(of_chosen, FDT_PROP_KEXEC_BUFFER, NULL);
> + if (!prop)
> + return -ENOENT;
> +
> + ret = do_get_kexec_buffer(prop->value, prop->length, &addr, &size);
> + if (ret)
> + return ret;
> +
> + ret = of_remove_property(of_chosen, prop);
> + if (ret)
> + return ret;
> +
> + return memblock_free(addr, size);

On the other hand you removed the spurious blank line that exists in
powerpc. Thanks. :-)

> +}
> +
> +#ifdef CONFIG_IMA

remove_ima_buffer() should exist even if CONFIG_IMA isn't set. If I
recall correctly, Mimi requested that kernels that are booted via kexec
should remove the IMA buffer even if they won't use it.

> +/**
> + * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
> + *
> + * The IMA measurement buffer is of no use to a subsequent kernel, so we always
> + * remove it from the device tree.
> + */
> +void remove_ima_buffer(void *fdt, int chosen_node)
> +{
> + int ret, len;
> + unsigned long addr;
> + size_t size;
> + const void *prop;
> +
> + prop = fdt_getprop(fdt, chosen_node, FDT_PROP_KEXEC_BUFFER, &len);
> + if (!prop)
> + return;
> +
> + ret = do_get_kexec_buffer(prop, len, &addr, &size);
> + fdt_delprop(fdt, chosen_node, FDT_PROP_KEXEC_BUFFER);
> + if (ret)
> + return;
> +
> + ret = delete_fdt_mem_rsv(fdt, addr, size);
> + if (!ret)
> + pr_debug("Removed old IMA buffer reservation.\n");
> +}
> +#endif /* CONFIG_IMA */
> +
> +#ifdef CONFIG_IMA_KEXEC
> +/**
> + * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
> + *
> + * Architectures should use this function to pass on the IMA buffer
> + * information to the next kernel.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
> + size_t size)
> +{
> + image->arch.ima_buffer_addr = load_addr;
> + image->arch.ima_buffer_size = size;
> + return 0;
> +}
> +
> +static int write_number(void *p, u64 value, int cells)
> +{
> + if (cells == 1) {
> + u32 tmp;
> +
> + if (value > U32_MAX)
> + return -EINVAL;
> +
> + tmp = cpu_to_be32(value);
> + memcpy(p, &tmp, sizeof(tmp));
> + } else if (cells == 2) {
> + u64 tmp;
> +
> + tmp = cpu_to_be64(value);
> + memcpy(p, &tmp, sizeof(tmp));
> + } else
> + return -EINVAL;
> + return 0;
> +}
> +
> +/**
> + * setup_ima_buffer - add IMA buffer information to the fdt
> + * @image: kexec image being loaded.
> + * @dtb: Flattened device tree for the next kernel.
> + * @chosen_node: Offset to the chosen node.
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int setup_ima_buffer(const struct kimage *image, void *dtb, int chosen_node)
> +{

Is there any particular reason to rename the fdt parameter to dtb?

> + int ret, addr_cells, size_cells, entry_size;
> + u8 value[16];
> +
> + remove_ima_buffer(dtb, chosen_node);

In the powerpc version, there's an if here to return early if
image->arch.ima_buffer_size == 0. Is there a reason why you removed it?

> +
> + ret = get_addr_size_cells(&addr_cells, &size_cells);
> + if (ret)
> + return ret;
> +
> + entry_size = 4 * (addr_cells + size_cells);
> +
> + if (entry_size > sizeof(value))
> + return -EINVAL;
> +
> + ret = write_number(value, image->arch.ima_buffer_addr, addr_cells);
> + if (ret)
> + return ret;
> +
> + ret = write_number(value + 4 * addr_cells, image->arch.ima_buffer_size,
> + size_cells);
> + if (ret)
> + return ret;
> +
> + ret = fdt_setprop(dtb, chosen_node, FDT_PROP_KEXEC_BUFFER, value,
> + entry_size);
> + if (ret < 0)
> + return -EINVAL;
> +
> + ret = fdt_add_mem_rsv(dtb, image->segment[0].mem,
> + image->segment[0].memsz);

powerpc uses image->arch.ima_buffer_addr and image->arch.ima_buffer_size
here. Why do you use segment[0] above?

> + if (ret)
> + return -EINVAL;
> +
> + return 0;
> +}
> +#endif /* CONFIG_IMA_KEXEC */
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index 58871333737a..c05ad6b74b62 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -21,6 +21,7 @@
> #include <linux/types.h>
> #include <linux/vmalloc.h>
> #include <asm/byteorder.h>
> +#include <asm/ima.h>
>
> /* relevant device tree properties */
> #define FDT_PROP_INITRD_START "linux,initrd-start"
> @@ -85,6 +86,11 @@ static int setup_dtb(struct kimage *image,
> goto out;
> }
>
> + /* add ima_buffer */
> + ret = setup_ima_buffer(image, dtb, off);
> + if (ret)
> + goto out;
> +
> /* add kaslr-seed */
> ret = fdt_delprop(dtb, off, FDT_PROP_KASLR_SEED);
> if (ret == -FDT_ERR_NOTFOUND)
> @@ -114,6 +120,39 @@ static int setup_dtb(struct kimage *image,
> */
> #define DTB_EXTRA_SPACE 0x1000
>
> +
> +/**
> + * delete_fdt_mem_rsv - delete memory reservation with given address and size
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
> +{
> + int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
> +
> + for (i = 0; i < num_rsvs; i++) {
> + uint64_t rsv_start, rsv_size;
> +
> + ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
> + if (ret) {
> + pr_err("Malformed device tree.\n");
> + return -EINVAL;
> + }
> +
> + if (rsv_start == start && rsv_size == size) {
> + ret = fdt_del_mem_rsv(fdt, i);
> + if (ret) {
> + pr_err("Error deleting device tree reservation.\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> + }
> + }
> +
> + return -ENOENT;
> +}

This functions is the same as the one in powerpc, and should be shared too.

--
Thiago Jung Bauermann
IBM Linux Technology Center

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