[RFC][PATCH 1/1] Carry ima measurement log for arm64 via kexec_file_load

[Prakhar Srivastava]

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@xxxxxxxxxxxxxxxxxxx>
---
 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
diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
new file mode 100644
index 000000000000..2c504281028d
--- /dev/null
+++ b/arch/arm64/include/asm/ima.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM64_IMA_H
+#define _ASM_ARM64_IMA_H
+
+#define FDT_PROP_KEXEC_BUFFER	"linux,ima-kexec-buffer"
+
+struct kimage;
+
+int ima_get_kexec_buffer(void **addr, size_t *size);
+int ima_free_kexec_buffer(void);
+
+#ifdef CONFIG_IMA
+void remove_ima_buffer(void *fdt, int chosen_node);
+#else
+static inline void remove_ima_buffer(void *fdt, int chosen_node) {}
+#endif
+
+#ifdef CONFIG_IMA_KEXEC
+int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
+			      size_t size);
+
+int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node);
+#else
+static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
+				   int chosen_node)
+{
+	remove_ima_buffer(fdt, chosen_node);
+	return 0;
+}
+#endif /* CONFIG_IMA_KEXEC */
+#endif /* _ASM_ARM64_IMA_H */
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 12a561a54128..ca1f9ad5c4d4 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -96,6 +96,8 @@ static inline void crash_post_resume(void) {}
 struct kimage_arch {
 	void *dtb;
 	unsigned long dtb_mem;
+	phys_addr_t ima_buffer_addr;
+	size_t ima_buffer_size;
 };
 
 extern const struct kexec_file_ops kexec_image_ops;
@@ -107,6 +109,8 @@ extern int load_other_segments(struct kimage *image,
 		unsigned long kernel_load_addr, unsigned long kernel_size,
 		char *initrd, unsigned long initrd_len,
 		char *cmdline);
+extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
+		unsigned long size);
 #endif
 
 #endif /* __ASSEMBLY__ */
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@xxxxxxxxxxxxxxxxxx>
+ *
+ * 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.
+ */
+
+#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)
+{
+
+	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);
+}
+
+#ifdef CONFIG_IMA
+/**
+ * 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)
+{
+	int ret, addr_cells, size_cells, entry_size;
+	u8 value[16];
+
+	remove_ima_buffer(dtb, chosen_node);
+
+	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);
+	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;
+}
+
 static int create_dtb(struct kimage *image,
 		      unsigned long initrd_load_addr, unsigned long initrd_len,
 		      char *cmdline, void **dtb)
-- 
2.17.1