This patch adds writing support for /dev/oldmem. This can be used to - Communicate between original kernel and kexeced kernel through write to some pages in original kernel. - Restore the memory contents of hibernated system in kexec based hibernation. Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx> --- arch/x86/kernel/crash_dump_32.c | 27 +++++++++++++++++++++++++++ drivers/char/mem.c | 32 ++++++++++++++++++++++++++++++++ include/linux/crash_dump.h | 2 ++ 3 files changed, 61 insertions(+) --- a/arch/x86/kernel/crash_dump_32.c +++ b/arch/x86/kernel/crash_dump_32.c @@ -59,6 +59,33 @@ ssize_t copy_oldmem_page(unsigned long p return csize; } +ssize_t write_oldmem_page(unsigned long pfn, const char *buf, + size_t csize, unsigned long offset, int userbuf) +{ + void *vaddr; + + if (!csize) + return 0; + + if (!userbuf) { + vaddr = kmap_atomic_pfn(pfn, KM_PTE0); + memcpy(vaddr + offset, buf, csize); + } else { + if (!kdump_buf_page) { + printk(KERN_WARNING "Kdump: Kdump buffer page not" + " allocated\n"); + return -EFAULT; + } + if (copy_from_user(kdump_buf_page, buf, csize)) + return -EFAULT; + vaddr = kmap_atomic_pfn(pfn, KM_PTE0); + memcpy(vaddr + offset, kdump_buf_page, csize); + } + kunmap_atomic(vaddr, KM_PTE0); + + return csize; +} + static int __init kdump_buf_page_init(void) { int ret = 0; --- a/include/linux/crash_dump.h +++ b/include/linux/crash_dump.h @@ -11,6 +11,8 @@ extern unsigned long long elfcorehdr_addr; extern ssize_t copy_oldmem_page(unsigned long, char *, size_t, unsigned long, int); +extern ssize_t write_oldmem_page(unsigned long, const char *, size_t, + unsigned long, int); extern const struct file_operations proc_vmcore_operations; extern struct proc_dir_entry *proc_vmcore; --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -348,6 +348,37 @@ static ssize_t read_oldmem(struct file * } return read; } + +/* + * Write memory corresponding to the old kernel. + */ +static ssize_t write_oldmem(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + unsigned long pfn, offset; + size_t write = 0, csize; + int rc = 0; + + while (count) { + pfn = *ppos / PAGE_SIZE; + if (pfn > saved_max_pfn) + return write; + + offset = (unsigned long)(*ppos % PAGE_SIZE); + if (count > PAGE_SIZE - offset) + csize = PAGE_SIZE - offset; + else + csize = count; + rc = write_oldmem_page(pfn, buf, csize, offset, 1); + if (rc < 0) + return rc; + buf += csize; + *ppos += csize; + write += csize; + count -= csize; + } + return write; +} #endif extern long vread(char *buf, char *addr, unsigned long count); @@ -783,6 +814,7 @@ static const struct file_operations full #ifdef CONFIG_CRASH_DUMP static const struct file_operations oldmem_fops = { .read = read_oldmem, + .write = write_oldmem, .open = open_oldmem, }; #endif _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm