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: Geert Uytterhoeven <geert@linux-m68k.org>

3 files changed, 83 insertions, 0 deletions

diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile
index 7ee5f00a9abb..2d5d9be16273 100644
--- a/arch/m68k/kernel/Makefile
+++ b/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
 
diff --git a/arch/m68k/kernel/bootinfo_proc.c b/arch/m68k/kernel/bootinfo_proc.c
new file mode 100644
index 000000000000..7ee853e1432b
--- /dev/null
+++ b/arch/m68k/kernel/bootinfo_proc.c
@@ -0,0 +1,80 @@
+/*
+ * 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);
diff --git a/arch/m68k/kernel/setup_mm.c b/arch/m68k/kernel/setup_mm.c
index 28abca421974..5b8ec4d5f8e8 100644
--- a/arch/m68k/kernel/setup_mm.c
+++ b/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;