riscv: kexec_file: Support loading Image binary file

This patch creates image_kexec_ops to load Image binary file
for kexec_file_load() syscall.

Signed-off-by: Song Shuai <songshuaishuai@tinylab.org>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250409193004.643839-3-bjorn@kernel.org
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

Author: Song Shuai

arch/riscv/include/asm/image.h

@@ -30,6 +30,8 @@
 			      RISCV_HEADER_VERSION_MINOR)
 
 #ifndef __ASSEMBLY__
+#define riscv_image_flag_field(flags, field)\
+			       (((flags) >> field##_SHIFT) & field##_MASK)
 /**
  * struct riscv_image_header - riscv kernel image header
  * @code0:		Executable code

arch/riscv/include/asm/kexec.h

@@ -56,6 +56,7 @@ extern riscv_kexec_method riscv_kexec_norelocate;
 
 #ifdef CONFIG_KEXEC_FILE
 extern const struct kexec_file_ops elf_kexec_ops;
+extern const struct kexec_file_ops image_kexec_ops;
 
 struct purgatory_info;
 int arch_kexec_apply_relocations_add(struct purgatory_info *pi,

arch/riscv/kernel/Makefile

@@ -107,7 +107,7 @@ obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_PARAVIRT)		+= paravirt.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o
-obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o machine_kexec_file.o
+obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o kexec_image.o machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_VMCORE_INFO)	+= vmcore_info.o
 

arch/riscv/kernel/kexec_image.c

@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RISC-V Kexec image loader
+ *
+ */
+
+#define pr_fmt(fmt)	"kexec_file(Image): " fmt
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/pe.h>
+#include <linux/string.h>
+#include <asm/byteorder.h>
+#include <asm/image.h>
+
+static int image_probe(const char *kernel_buf, unsigned long kernel_len)
+{
+	const struct riscv_image_header *h = (const struct riscv_image_header *)kernel_buf;
+
+	if (!h || kernel_len < sizeof(*h))
+		return -EINVAL;
+
+	/* According to Documentation/riscv/boot-image-header.rst,
+	 * use "magic2" field to check when version >= 0.2.
+	 */
+
+	if (h->version >= RISCV_HEADER_VERSION &&
+	    memcmp(&h->magic2, RISCV_IMAGE_MAGIC2, sizeof(h->magic2)))
+		return -EINVAL;
+
+	return 0;
+}
+
+static void *image_load(struct kimage *image,
+			char *kernel, unsigned long kernel_len,
+			char *initrd, unsigned long initrd_len,
+			char *cmdline, unsigned long cmdline_len)
+{
+	struct riscv_image_header *h;
+	u64 flags;
+	bool be_image, be_kernel;
+	struct kexec_buf kbuf;
+	int ret;
+
+	/* Check Image header */
+	h = (struct riscv_image_header *)kernel;
+	if (!h->image_size) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Check endianness */
+	flags = le64_to_cpu(h->flags);
+	be_image = riscv_image_flag_field(flags, RISCV_IMAGE_FLAG_BE);
+	be_kernel = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
+	if (be_image != be_kernel) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Load the kernel image */
+	kbuf.image = image;
+	kbuf.buf_min = 0;
+	kbuf.buf_max = ULONG_MAX;
+	kbuf.top_down = false;
+
+	kbuf.buffer = kernel;
+	kbuf.bufsz = kernel_len;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf.memsz = le64_to_cpu(h->image_size);
+	kbuf.buf_align = le64_to_cpu(h->text_offset);
+
+	ret = kexec_add_buffer(&kbuf);
+	if (ret) {
+		pr_err("Error add kernel image ret=%d\n", ret);
+		goto out;
+	}
+
+	image->start = kbuf.mem;
+
+	pr_info("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		kbuf.mem, kbuf.bufsz, kbuf.memsz);
+
+	ret = load_extra_segments(image, kbuf.mem, kbuf.memsz,
+				  initrd, initrd_len, cmdline, cmdline_len);
+
+out:
+	return ret ? ERR_PTR(ret) : NULL;
+}
+
+const struct kexec_file_ops image_kexec_ops = {
+	.probe = image_probe,
+	.load = image_load,
+};

arch/riscv/kernel/machine_kexec_file.c

@@ -18,6 +18,7 @@
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 	&elf_kexec_ops,
+	&image_kexec_ops,
 	NULL
 };