powerpc: Refactor kexec functions to move arch independent code to IMA

The functions ima_get_kexec_buffer(), ima_free_kexec_buffer(),
remove_ima_buffer(), and delete_fdt_mem_rsv() that handle carrying
forward the IMA measurement logs on kexec for powerpc do not have
architecture specific code, but they are currently defined for
powerpc only.

Move these functions to IMA subsystem so that it can be used for other
architectures as well. A later patch in this series will use these
functions for carrying forward the IMA measurement log for ARM64.
Rename remove_ima_buffer() to ima_remove_kexec_buffer().

Define FDT_PROP_IMA_KEXEC_BUFFER for the chosen node, namely
"linux,ima-kexec-buffer", that is added to the DTB to hold
the address and the size of the memory reserved to carry
the IMA measurement log.

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>

arch/powerpc/include/asm/ima.h

@@ -4,15 +4,6 @@
 
 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);
@@ -22,7 +13,7 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node);
 static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
 				   int chosen_node)
 {
-	remove_ima_buffer(fdt, chosen_node);
+	ima_remove_kexec_buffer(fdt, chosen_node);
 	return 0;
 }
 #endif /* CONFIG_IMA_KEXEC */

arch/powerpc/include/asm/kexec.h

@@ -126,7 +126,6 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
 int setup_new_fdt(const struct kimage *image, void *fdt,
 		  unsigned long initrd_load_addr, unsigned long initrd_len,
 		  const char *cmdline);
-int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size);
 
 #ifdef CONFIG_PPC64
 struct kexec_buf;

arch/powerpc/kexec/file_load.c

@@ -18,6 +18,7 @@
 #include <linux/kexec.h>
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
+#include <linux/kexec.h>
 #include <asm/setup.h>
 #include <asm/ima.h>
 
@@ -109,38 +110,6 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
 	return 0;
 }
 
-/**
- * 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;
-}
-
 /*
  * setup_new_fdt - modify /chosen and memory reservation for the next kernel
  * @image:		kexec image being loaded.

arch/powerpc/kexec/ima.c

@@ -9,6 +9,7 @@
 #include <linux/slab.h>
 #include <linux/kexec.h>
 #include <linux/of.h>
+#include <linux/ima.h>
 #include <linux/memblock.h>
 #include <linux/libfdt.h>
 
@@ -28,105 +29,6 @@ static int get_addr_size_cells(int *addr_cells, int *size_cells)
 	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, "linux,ima-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, "linux,ima-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);
-
-}
-
-/**
- * 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, "linux,ima-kexec-buffer", &len);
-	if (!prop)
-		return;
-
-	ret = do_get_kexec_buffer(prop, len, &addr, &size);
-	fdt_delprop(fdt, chosen_node, "linux,ima-kexec-buffer");
-	if (ret)
-		return;
-
-	ret = delete_fdt_mem_rsv(fdt, addr, size);
-	if (!ret)
-		pr_debug("Removed old IMA buffer reservation.\n");
-}
-
 #ifdef CONFIG_IMA_KEXEC
 /**
  * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
@@ -179,7 +81,7 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
 	int ret, addr_cells, size_cells, entry_size;
 	u8 value[16];
 
-	remove_ima_buffer(fdt, chosen_node);
+	ima_remove_kexec_buffer(fdt, chosen_node);
 	if (!image->arch.ima_buffer_size)
 		return 0;
 
@@ -201,7 +103,7 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
 	if (ret)
 		return ret;
 
-	ret = fdt_setprop(fdt, chosen_node, "linux,ima-kexec-buffer", value,
+	ret = fdt_setprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER, value,
 			  entry_size);
 	if (ret < 0)
 		return -EINVAL;

include/linux/ima.h

@@ -26,6 +26,7 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 extern void ima_post_path_mknod(struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
+extern void ima_remove_kexec_buffer(void *fdt, int chosen_node);
 
 #ifdef CONFIG_IMA_KEXEC
 extern void ima_add_kexec_buffer(struct kimage *image);
@@ -104,6 +105,7 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
 }
 
 static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
+static inline void ima_remove_kexec_buffer(void *fdt, int chosen_node) {}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC

include/linux/kexec.h

@@ -223,8 +223,19 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
 				   unsigned long long mend);
 extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
 				       void **addr, unsigned long *sz);
+
+extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
+			      unsigned long size);
 #endif /* CONFIG_KEXEC_FILE */
 
+#ifndef CONFIG_KEXEC_FILE
+static inline int delete_fdt_mem_rsv(void *fdt, unsigned long start,
+				     unsigned long size)
+{
+	return 0;
+}
+#endif /* ifndef CONFIG_KEXEC_FILE */
+
 #ifdef CONFIG_KEXEC_ELF
 struct kexec_elf_info {
 	/*

include/linux/libfdt.h

@@ -5,4 +5,7 @@
 #include <linux/libfdt_env.h>
 #include "../../scripts/dtc/libfdt/libfdt.h"
 
+/* Common device tree properties */
+#define FDT_PROP_IMA_KEXEC_BUFFER	"linux,ima-kexec-buffer"
+
 #endif /* _INCLUDE_LIBFDT_H_ */

security/integrity/ima/Makefile

@@ -7,10 +7,11 @@
 obj-$(CONFIG_IMA) += ima.o
 
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
-	 ima_policy.o ima_template.o ima_template_lib.o
+	 ima_policy.o ima_template.o ima_template_lib.o ima_fdt.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
 ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
 ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
 ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
+ima-$(CONFIG_KEXEC_FILE) += ima_kexec_file.o

security/integrity/ima/ima.h

@@ -167,6 +167,8 @@ void ima_init_template_list(void);
 int __init ima_init_digests(void);
 int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 			  void *lsm_data);
+int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
+			size_t *size);
 
 /*
  * used to protect h_table and sha_table

security/integrity/ima/ima_fdt.c

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * ima_fdt.c
+ *	Implements functions to handle IMA buffer in device tree
+ */
+
+#include <linux/libfdt.h>
+#include <linux/kexec.h>
+#include <linux/ima.h>
+#include "ima.h"
+
+/**
+ * do_get_kexec_buffer - Get address and size of IMA kexec buffer
+ *
+ * @prop: IMA kexec buffer node in the device tree
+ * @addr: Return address of the node
+ * @size: Return size of the node
+ */
+int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
+			size_t *size)
+{
+	int addr_cells, 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);
+
+	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_remove_kexec_buffer - remove the IMA buffer property and
+ *			     reservation from @fdt
+ *
+ * @fdt: Flattened Device Tree to update
+ * @chosen_node: Offset to the chosen node in the device tree
+ *
+ * The IMA measurement buffer is of no use to a subsequent kernel,
+ * so we always remove it from the device tree.
+ */
+void ima_remove_kexec_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_IMA_KEXEC_BUFFER, &len);
+	if (!prop) {
+		pr_err("Unable to find the ima kexec buffer node\n");
+		return;
+	}
+
+	ret = do_get_kexec_buffer(prop, len, &addr, &size);
+	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
+	if (ret) {
+		pr_err("Unable to delete the ima kexec buffer node\n");
+		return;
+	}
+
+	ret = delete_fdt_mem_rsv(fdt, addr, size);
+	if (!ret)
+		pr_err("Removed old IMA buffer reservation.\n");
+}