diff options
| -rw-r--r-- | Documentation/devices.txt | 1 | ||||
| -rw-r--r-- | drivers/char/mem.c | 74 |
2 files changed, 75 insertions, 0 deletions
diff --git a/Documentation/devices.txt b/Documentation/devices.txt index bb67cf25010e..0f515175c72a 100644 --- a/Documentation/devices.txt +++ b/Documentation/devices.txt @@ -94,6 +94,7 @@ Your cooperation is appreciated. 9 = /dev/urandom Faster, less secure random number gen. 10 = /dev/aio Asyncronous I/O notification interface 11 = /dev/kmsg Writes to this come out as printk's + 12 = /dev/oldmem Access to crash dump from kexec kernel 1 block RAM disk 0 = /dev/ram0 First RAM disk 1 = /dev/ram1 Second RAM disk diff --git a/drivers/char/mem.c b/drivers/char/mem.c index e3085b22a365..01b3c17ca851 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -23,6 +23,8 @@ #include <linux/devfs_fs_kernel.h> #include <linux/ptrace.h> #include <linux/device.h> +#include <linux/highmem.h> +#include <linux/crash_dump.h> #include <linux/backing-dev.h> #include <asm/uaccess.h> @@ -273,6 +275,62 @@ static int mmap_kmem(struct file * file, struct vm_area_struct * vma) return mmap_mem(file, vma); } +#ifdef CONFIG_CRASH_DUMP +/* + * Read memory corresponding to the old kernel. + * If we are reading from the reserved section, which is + * actually used by the current kernel, we just return zeroes. + * Or if we are reading from the first 640k, we return from the + * backed up area. + */ +static ssize_t read_oldmem(struct file * file, char * buf, + size_t count, loff_t *ppos) +{ + unsigned long pfn; + unsigned backup_start, backup_end, relocate_start; + size_t read=0, csize; + + backup_start = CRASH_BACKUP_BASE / PAGE_SIZE; + backup_end = backup_start + (CRASH_BACKUP_SIZE / PAGE_SIZE); + relocate_start = (CRASH_BACKUP_BASE + CRASH_BACKUP_SIZE) / PAGE_SIZE; + + while(count) { + pfn = *ppos / PAGE_SIZE; + + csize = (count > PAGE_SIZE) ? PAGE_SIZE : count; + + /* Perform translation (see comment above) */ + if ((pfn >= backup_start) && (pfn < backup_end)) { + if (clear_user(buf, csize)) { + read = -EFAULT; + goto done; + } + + goto copy_done; + } else if (pfn < (CRASH_RELOCATE_SIZE / PAGE_SIZE)) + pfn += relocate_start; + + if (pfn > saved_max_pfn) { + read = 0; + goto done; + } + + if (copy_oldmem_page(pfn, buf, csize, 1)) { + read = -EFAULT; + goto done; + } + +copy_done: + buf += csize; + *ppos += csize; + read += csize; + count -= csize; + } +done: + return read; +} +#endif + extern long vread(char *buf, char *addr, unsigned long count); extern long vwrite(char *buf, char *addr, unsigned long count); @@ -721,6 +779,7 @@ static int open_port(struct inode * inode, struct file * filp) #define read_full read_zero #define open_mem open_port #define open_kmem open_mem +#define open_oldmem open_mem static struct file_operations mem_fops = { .llseek = memory_lseek, @@ -770,6 +829,13 @@ static struct file_operations full_fops = { .write = write_full, }; +#ifdef CONFIG_CRASH_DUMP +static struct file_operations oldmem_fops = { + .read = read_oldmem, + .open = open_oldmem, +}; +#endif + static ssize_t kmsg_write(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { @@ -825,6 +891,11 @@ static int memory_open(struct inode * inode, struct file * filp) case 11: filp->f_op = &kmsg_fops; break; +#ifdef CONFIG_CRASH_DUMP + case 12: + filp->f_op = &oldmem_fops; + break; +#endif default: return -ENXIO; } @@ -854,6 +925,9 @@ static const struct { {8, "random", S_IRUGO | S_IWUSR, &random_fops}, {9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops}, {11,"kmsg", S_IRUGO | S_IWUSR, &kmsg_fops}, +#ifdef CONFIG_CRASH_DUMP + {12,"oldmem", S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops}, +#endif }; static struct class *mem_class; |