m68k: Add support to export bootinfo in procfs

Add optional support to export the bootinfo used to boot the kernel in a
"bootinfo" file in procfs.  This is useful with kexec.

This is based on the similar feature for ATAGS on ARM.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/Kconfig

@@ -104,6 +104,13 @@ config KEXEC
 	  interface is strongly in flux, so no good recommendation can be
 	  made.
 
+config BOOTINFO_PROC
+	bool "Export bootinfo in procfs"
+	depends on KEXEC && M68KCLASSIC
+	help
+	  Say Y to export the bootinfo used to boot the kernel in a
+	  "bootinfo" file in procfs.  This is useful with kexec.
+
 menu "Platform setup"
 
 source arch/m68k/Kconfig.cpu

arch/m68k/include/asm/bootinfo.h

@@ -13,4 +13,16 @@
 
 #include <uapi/asm/bootinfo.h>
 
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_BOOTINFO_PROC
+extern void save_bootinfo(const struct bi_record *bi);
+#else
+static inline void save_bootinfo(const struct bi_record *bi) {}
+#endif
+
+#endif /* __ASSEMBLY__ */
+
+
 #endif /* _M68K_BOOTINFO_H */

arch/m68k/kernel/Makefile

@@ -23,4 +23,5 @@ obj-$(CONFIG_PCI) += pcibios.o
 obj-$(CONFIG_HAS_DMA)	+= dma.o
 
 obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_BOOTINFO_PROC)	+= bootinfo_proc.o
 

arch/m68k/kernel/bootinfo_proc.c

+/*
+ * Based on arch/arm/kernel/atags_proc.c
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/printk.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include <asm/bootinfo.h>
+#include <asm/byteorder.h>
+
+
+static char bootinfo_tmp[1536] __initdata;
+
+static void *bootinfo_copy;
+static size_t bootinfo_size;
+
+static ssize_t bootinfo_read(struct file *file, char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	return simple_read_from_buffer(buf, count, ppos, bootinfo_copy,
+				       bootinfo_size);
+}
+
+static const struct file_operations bootinfo_fops = {
+	.read = bootinfo_read,
+	.llseek = default_llseek,
+};
+
+void __init save_bootinfo(const struct bi_record *bi)
+{
+	const void *start = bi;
+	size_t size = sizeof(bi->tag);
+
+	while (be16_to_cpu(bi->tag) != BI_LAST) {
+		uint16_t n = be16_to_cpu(bi->size);
+		size += n;
+		bi = (struct bi_record *)((unsigned long)bi + n);
+	}
+
+	if (size > sizeof(bootinfo_tmp)) {
+		pr_err("Cannot save %zu bytes of bootinfo\n", size);
+		return;
+	}
+
+	pr_info("Saving %zu bytes of bootinfo\n", size);
+	memcpy(bootinfo_tmp, start, size);
+	bootinfo_size = size;
+}
+
+static int __init init_bootinfo_procfs(void)
+{
+	/*
+	 * This cannot go into save_bootinfo() because kmalloc and proc don't
+	 * work yet when it is called.
+	 */
+	struct proc_dir_entry *pde;
+
+	if (!bootinfo_size)
+		return -EINVAL;
+
+	bootinfo_copy = kmalloc(bootinfo_size, GFP_KERNEL);
+	if (!bootinfo_copy)
+		return -ENOMEM;
+
+	memcpy(bootinfo_copy, bootinfo_tmp, bootinfo_size);
+
+	pde = proc_create_data("bootinfo", 0400, NULL, &bootinfo_fops, NULL);
+	if (!pde) {
+		kfree(bootinfo_copy);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+arch_initcall(init_bootinfo_procfs);

arch/m68k/kernel/setup_mm.c

@@ -146,6 +146,8 @@ static void __init m68k_parse_bootinfo(const struct bi_record *record)
 {
 	uint16_t tag;
 
+	save_bootinfo(record);
+
 	while ((tag = be16_to_cpu(record->tag)) != BI_LAST) {
 		int unknown = 0;
 		const void *data = record->data;