Хозяйке на заметку: Пач against 2.6.34.7 чтобы создавалось устройство /dev/one, которое возвращает 0xFF при чтении из него. diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 53dd7d0..21590ae 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -789,6 +789,24 @@ static ssize_t read_zero(struct file *file, char __user *buf, return written ? written : -EFAULT; } +static ssize_t read_one(struct file * file, char __user * buf, + size_t count, loff_t *ppos) +{ + size_t written; + unsigned long unwritten; + static int one = ~0; + + for (written = 0; written < count; written++) { + unwritten = copy_to_user(&buf[written], &one, 1); + if (unwritten) + break; + cond_resched(); + } + + return written ? written : -EFAULT; +} + + static int mmap_zero(struct file *file, struct vm_area_struct *vma) { #ifndef CONFIG_MMU @@ -860,6 +878,10 @@ static int open_port(struct inode * inode, struct file * filp) #define open_mem open_port #define open_kmem open_mem #define open_oldmem open_mem +#define one_lseek null_lseek +#define write_one write_null +#define mmap_one mmap_zero + #ifndef ARCH_HAS_DEV_MEM static const struct file_operations mem_fops = { @@ -930,6 +952,13 @@ static const struct file_operations oldmem_fops = { }; #endif +static const struct file_operations one_fops = { + .llseek = one_lseek, + .read = read_one, + .write = write_one, + .mmap = mmap_one, +}; + static ssize_t kmsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { @@ -977,6 +1006,7 @@ static const struct memdev { #ifdef CONFIG_CRASH_DUMP [12] = { "oldmem", 0, &oldmem_fops, NULL }, #endif + [13] = { "one", 0, &one_fops, NULL }, }; static int memory_open(struct inode *inode, struct file *filp)