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>

1 files changed, 122 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
new file mode 100644
index 000000000000..8e99d2f7165e
--- /dev/null
+++ b/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;
+}