LoongArch: Add preparatory infrastructure for kexec_file

Add some preparatory infrastructure:
- Add command line processing.
- Add support for loading other segments.
- Other minor modifications.

This initrd will be passed to the second kernel via the command line
'initrd=start,size'.

The 'kexec_file' command line parameter indicates that the kernel is
loaded via kexec_file.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -633,6 +633,15 @@ config CPU_HAS_PREFETCH
 config ARCH_SUPPORTS_KEXEC
 	def_bool y
 
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool 64BIT
+
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool 64BIT
+	depends on KEXEC_FILE
+	select RELOCATABLE
+	select HAVE_IMA_KEXEC if IMA
+
 config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
 

arch/loongarch/include/asm/kexec.h

@@ -41,6 +41,16 @@ struct kimage_arch {
 	unsigned long systable_ptr;
 };
 
+#ifdef CONFIG_KEXEC_FILE
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image);
+#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
+
+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, unsigned long cmdline_len);
+#endif
+
 typedef void (*do_kexec_t)(unsigned long efi_boot,
 			   unsigned long cmdline_ptr,
 			   unsigned long systable_ptr,

arch/loongarch/kernel/Makefile

@@ -62,6 +62,7 @@ obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_RELOCATABLE)	+= relocate.o
 
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_UNWINDER_GUESS)	+= unwind_guess.o

arch/loongarch/kernel/machine_kexec.c

@@ -70,18 +70,28 @@ int machine_kexec_prepare(struct kimage *kimage)
 	kimage->arch.efi_boot = fw_arg0;
 	kimage->arch.systable_ptr = fw_arg2;
 
-	/* Find the command line */
-	for (i = 0; i < kimage->nr_segments; i++) {
-		if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, strlen(bootloader))) {
-			if (!copy_from_user(cmdline_ptr, kimage->segment[i].buf, COMMAND_LINE_SIZE))
-				kimage->arch.cmdline_ptr = (unsigned long)cmdline_ptr;
-			break;
+	if (kimage->file_mode == 1) {
+		/*
+		 * kimage->cmdline_buf will be released in kexec_file_load, so copy
+		 * to the KEXEC_CMDLINE_ADDR safe area.
+		 */
+		memcpy((void *)KEXEC_CMDLINE_ADDR, (void *)kimage->arch.cmdline_ptr,
+					strlen((char *)kimage->arch.cmdline_ptr) + 1);
+		kimage->arch.cmdline_ptr = (unsigned long)KEXEC_CMDLINE_ADDR;
+	} else {
+		/* Find the command line */
+		for (i = 0; i < kimage->nr_segments; i++) {
+			if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, strlen(bootloader))) {
+				if (!copy_from_user(cmdline_ptr, kimage->segment[i].buf, COMMAND_LINE_SIZE))
+					kimage->arch.cmdline_ptr = (unsigned long)cmdline_ptr;
+				break;
+			}
 		}
-	}
 
-	if (!kimage->arch.cmdline_ptr) {
-		pr_err("Command line not included in the provided image\n");
-		return -EINVAL;
+		if (!kimage->arch.cmdline_ptr) {
+			pr_err("Command line not included in the provided image\n");
+			return -EINVAL;
+		}
 	}
 
 	/* kexec/kdump need a safe page to save reboot_code_buffer */
@@ -287,9 +297,10 @@ void machine_kexec(struct kimage *image)
 	/* We do not want to be bothered. */
 	local_irq_disable();
 
-	pr_notice("EFI boot flag 0x%lx\n", efi_boot);
-	pr_notice("Command line at 0x%lx\n", cmdline_ptr);
-	pr_notice("System table at 0x%lx\n", systable_ptr);
+	pr_notice("EFI boot flag: 0x%lx\n", efi_boot);
+	pr_notice("Command line addr: 0x%lx\n", cmdline_ptr);
+	pr_notice("Command line string: %s\n", (char *)cmdline_ptr);
+	pr_notice("System table addr: 0x%lx\n", systable_ptr);
 	pr_notice("We will call new kernel at 0x%lx\n", start_addr);
 	pr_notice("Bye ...\n");
 

arch/loongarch/kernel/machine_kexec_file.c

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kexec_file for LoongArch
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ *
+ * Most code is derived from LoongArch port of kexec-tools
+ */
+
+#define pr_fmt(fmt) "kexec_file: " fmt
+
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/memblock.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <asm/bootinfo.h>
+
+const struct kexec_file_ops * const kexec_file_loaders[] = {
+	NULL
+};
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+	vfree(image->elf_headers);
+	image->elf_headers = NULL;
+	image->elf_headers_sz = 0;
+
+	return kexec_image_post_load_cleanup_default(image);
+}
+
+/* Add the "kexec_file" command line parameter to command line. */
+static void cmdline_add_loader(unsigned long *cmdline_tmplen, char *modified_cmdline)
+{
+	int loader_strlen;
+
+	loader_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "kexec_file ");
+	*cmdline_tmplen += loader_strlen;
+}
+
+/* Add the "initrd=start,size" command line parameter to command line. */
+static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmplen,
+				char *modified_cmdline, unsigned long initrd)
+{
+	int initrd_strlen;
+
+	initrd_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "initrd=0x%lx,0x%lx ",
+		initrd, image->initrd_buf_len);
+	*cmdline_tmplen += initrd_strlen;
+}
+
+/*
+ * Try to add the initrd to the image. If it is not possible to find valid
+ * locations, this function will undo changes to the image and return non zero.
+ */
+int load_other_segments(struct kimage *image,
+			unsigned long kernel_load_addr, unsigned long kernel_size,
+			char *initrd, unsigned long initrd_len, char *cmdline, unsigned long cmdline_len)
+{
+	int ret = 0;
+	unsigned long cmdline_tmplen = 0;
+	unsigned long initrd_load_addr = 0;
+	unsigned long orig_segments = image->nr_segments;
+	char *modified_cmdline = NULL;
+	struct kexec_buf kbuf;
+
+	kbuf.image = image;
+	/* Don't allocate anything below the kernel */
+	kbuf.buf_min = kernel_load_addr + kernel_size;
+
+	modified_cmdline = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
+	if (!modified_cmdline)
+		return -EINVAL;
+
+	cmdline_add_loader(&cmdline_tmplen, modified_cmdline);
+	/* Ensure it's null terminated */
+	modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
+
+	/* Load initrd */
+	if (initrd) {
+		kbuf.buffer = initrd;
+		kbuf.bufsz = initrd_len;
+		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+		kbuf.memsz = initrd_len;
+		kbuf.buf_align = 0;
+		/* within 1GB-aligned window of up to 32GB in size */
+		kbuf.buf_max = round_down(kernel_load_addr, SZ_1G) + (unsigned long)SZ_1G * 32;
+		kbuf.top_down = false;
+
+		ret = kexec_add_buffer(&kbuf);
+		if (ret < 0)
+			goto out_err;
+		initrd_load_addr = kbuf.mem;
+
+		kexec_dprintk("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+			      initrd_load_addr, kbuf.bufsz, kbuf.memsz);
+
+		/* Add the initrd=start,size parameter to the command line */
+		cmdline_add_initrd(image, &cmdline_tmplen, modified_cmdline, initrd_load_addr);
+	}
+
+	if (cmdline_len + cmdline_tmplen > COMMAND_LINE_SIZE) {
+		pr_err("Appending command line exceeds COMMAND_LINE_SIZE\n");
+		ret = -EINVAL;
+		goto out_err;
+	}
+
+	memcpy(modified_cmdline + cmdline_tmplen, cmdline, cmdline_len);
+	cmdline = modified_cmdline;
+	image->arch.cmdline_ptr = (unsigned long)cmdline;
+
+	return 0;
+
+out_err:
+	image->nr_segments = orig_segments;
+	kfree(modified_cmdline);
+	return ret;
+}