From: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx> There is no possibility to clear additional kmsg buffers, get size of them or know what size should be passed to read file operation (too small size causes it to retrun -EINVAL). Add following ioctls which solve those issues: * KMSG_CMD_GET_BUF_SIZE * KMSG_CMD_GET_READ_SIZE_MAX * KMSG_CMD_CLEAR Signed-off-by: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx> Signed-off-by: Paul Osmialowski <p.osmialowsk@xxxxxxxxxxx> --- Documentation/ioctl/ioctl-number.txt | 2 +- include/uapi/linux/kmsg_ioctl.h | 15 ++++++++++ kernel/printk/kmsg.c | 57 ++++++++++++++++++++++++++++++++++-- 3 files changed, 71 insertions(+), 3 deletions(-) diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt index 76dec8b..d36bb04 100644 --- a/Documentation/ioctl/ioctl-number.txt +++ b/Documentation/ioctl/ioctl-number.txt @@ -319,7 +319,7 @@ Code Seq#(hex) Include File Comments <mailto:vgo@xxxxxxxx> 0xB1 00-1F PPPoX <mailto:mostrows@xxxxxxxxxxxxxxxxx> 0xB3 00 linux/mmc/ioctl.h -0xBB 00-02 uapi/linux/kmsg_ioctl.h +0xBB 00-83 uapi/linux/kmsg_ioctl.h 0xC0 00-0F linux/usb/iowarrior.h 0xCA 00-0F uapi/misc/cxl.h 0xCA 80-8F uapi/scsi/cxlflash_ioctl.h diff --git a/include/uapi/linux/kmsg_ioctl.h b/include/uapi/linux/kmsg_ioctl.h index 89c0c61..2389d9f 100644 --- a/include/uapi/linux/kmsg_ioctl.h +++ b/include/uapi/linux/kmsg_ioctl.h @@ -27,4 +27,19 @@ struct kmsg_cmd_buffer_add { struct kmsg_cmd_buffer_add) #define KMSG_CMD_BUFFER_DEL _IOW(KMSG_IOCTL_MAGIC, 0x01, int) +/* + * A ioctl interface for kmsg* devices. + * + * KMSG_CMD_GET_BUF_SIZE: Retrieve cyclic log buffer size associated with + * device. + * KMSG_CMD_GET_READ_SIZE_MAX: Retrieve max size of data read by kmsg read + * operation. + * KMSG_CMD_CLEAR: Clears cyclic log buffer. After that operation + * there is no data to read from buffer unless + * logs are written. + */ +#define KMSG_CMD_GET_BUF_SIZE _IOR(KMSG_IOCTL_MAGIC, 0x80, __u32) +#define KMSG_CMD_GET_READ_SIZE_MAX _IOR(KMSG_IOCTL_MAGIC, 0x81, __u32) +#define KMSG_CMD_CLEAR _IO(KMSG_IOCTL_MAGIC, 0x82) + #endif diff --git a/kernel/printk/kmsg.c b/kernel/printk/kmsg.c index f91a64a..0f56fc9 100644 --- a/kernel/printk/kmsg.c +++ b/kernel/printk/kmsg.c @@ -246,8 +246,9 @@ static loff_t kmsg_llseek(struct log_buffer *log_b, struct file *file, } /* * The first record after the last SYSLOG_ACTION_CLEAR, - * like issued by 'dmesg -c'. Reading /dev/kmsg itself - * changes no global state, and does not clear anything. + * like issued by 'dmesg -c' or KMSG_CMD_CLEAR ioctl + * command. Reading /dev/kmsg itself changes no global + * state, and does not clear anything. */ user->idx = log_b->clear_idx; user->seq = log_b->clear_seq; @@ -390,6 +391,56 @@ static int devkmsg_open(struct inode *inode, struct file *file) return ret; } +static long kmsg_ioctl(struct log_buffer *log_b, unsigned int cmd, + unsigned long arg) +{ + void __user *argp = (void __user *)arg; + static const u32 read_size_max = CONSOLE_EXT_LOG_MAX; + + switch (cmd) { + case KMSG_CMD_GET_BUF_SIZE: + if (copy_to_user(argp, &log_b->len, sizeof(u32))) + return -EFAULT; + break; + case KMSG_CMD_GET_READ_SIZE_MAX: + if (copy_to_user(argp, &read_size_max, sizeof(u32))) + return -EFAULT; + break; + case KMSG_CMD_CLEAR: + if (!capable(CAP_SYSLOG)) + return -EPERM; + raw_spin_lock_irq(&log_b->lock); + log_b->clear_seq = log_b->next_seq; + log_b->clear_idx = log_b->next_idx; + raw_spin_unlock_irq(&log_b->lock); + break; + default: + return -ENOTTY; + } + return 0; +} + +static long devkmsg_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + long ret = -ENXIO; + int minor = iminor(file->f_inode); + struct log_buffer *log_b; + + if (minor == log_buf.minor) + return kmsg_ioctl(&log_buf, cmd, arg); + + rcu_read_lock(); + list_for_each_entry_rcu(log_b, &log_buf.list, list) { + if (log_b->minor == minor) { + ret = kmsg_ioctl(log_b, cmd, arg); + break; + } + } + rcu_read_unlock(); + return ret; +} + static int devkmsg_release(struct inode *inode, struct file *file) { struct devkmsg_user *user = file->private_data; @@ -408,6 +459,8 @@ const struct file_operations kmsg_fops = { .write_iter = devkmsg_write, .llseek = devkmsg_llseek, .poll = devkmsg_poll, + .unlocked_ioctl = devkmsg_ioctl, + .compat_ioctl = devkmsg_ioctl, .release = devkmsg_release, }; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
