This provides a bootstrap and ongoing emergency console which is intended to be available from very early during boot and at all times thereafter, in contrast with alternatives such as UDP-based syslogd, or logging in via ssh. The protocol is based on a simple shared-memory ring buffer. Signed-off-by: Ian Pratt Signed-off-by: Christian Limpach Signed-off-by: Chris Wright Cc: Alan --- arch/i386/kernel/early_printk.c | 2 drivers/Makefile | 3 drivers/xen/Makefile | 1 drivers/xen/console/Makefile | 2 drivers/xen/console/console.c | 585 +++++++++++++++++++++++++++++++++++ drivers/xen/console/xencons_ring.c | 144 ++++++++ include/xen/xencons.h | 14 init/main.c | 2 8 files changed, 753 insertions(+) =================================================================== --- a/arch/i386/kernel/early_printk.c +++ b/arch/i386/kernel/early_printk.c @@ -1,2 +1,4 @@ +#ifndef CONFIG_XEN #include "../../x86_64/kernel/early_printk.c" +#endif =================================================================== --- a/drivers/Makefile +++ b/drivers/Makefile @@ -14,6 +14,9 @@ obj-$(CONFIG_ACPI) += acpi/ # was used and do nothing if so obj-$(CONFIG_PNP) += pnp/ obj-$(CONFIG_ARM_AMBA) += amba/ + +# Xen is the default console when running as a guest +obj-$(CONFIG_XEN) += xen/ # char/ comes before serial/ etc so that the VT console is the boot-time # default. =================================================================== --- /dev/null +++ b/drivers/xen/Makefile @@ -0,0 +1,1 @@ +obj-y += console/ =================================================================== --- /dev/null +++ b/drivers/xen/console/Makefile @@ -0,0 +1,2 @@ + +obj-y := console.o xencons_ring.o =================================================================== --- /dev/null +++ b/drivers/xen/console/console.c @@ -0,0 +1,585 @@ +/****************************************************************************** + * console.c + * + * Virtual console driver. + * + * Copyright (c) 2002-2004, K A Fraser. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 + * as published by the Free Software Foundation; or, when distributed + * separately from the Linux kernel or incorporated into other + * software packages, subject to the following license: + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this source file (the "Software"), to deal in the Software without + * restriction, including without limitation the rights to use, copy, modify, + * merge, publish, distribute, sublicense, and/or sell copies of the Software, + * and to permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include + +MODULE_LICENSE("Dual BSD/GPL"); + +static int xc_disabled = 0; +static int xc_num = -1; + +/* /dev/xvc0 device number allocated by lanana.org. */ +#define XEN_XVC_MAJOR 204 +#define XEN_XVC_MINOR 191 + +#ifdef CONFIG_MAGIC_SYSRQ +static unsigned long sysrq_requested; +#endif + +static int __init xencons_setup(char *str) +{ + if (!strcmp(str, "off")) + xc_disabled = 1; + return 1; +} +__setup("xencons=", xencons_setup); + +/* The kernel and user-land drivers share a common transmit buffer. */ +static unsigned int wbuf_size = 4096; +#define WBUF_MASK(_i) ((_i)&(wbuf_size-1)) +static char *wbuf; +static unsigned int wc, wp; /* write_cons, write_prod */ + +static int __init xencons_bufsz_setup(char *str) +{ + unsigned int goal; + goal = simple_strtoul(str, NULL, 0); + if (goal) { + goal = roundup_pow_of_two(goal); + if (wbuf_size < goal) + wbuf_size = goal; + } + return 1; +} +__setup("xencons_bufsz=", xencons_bufsz_setup); + +/* This lock protects accesses to the common transmit buffer. */ +static DEFINE_SPINLOCK(xencons_lock); + +/* Common transmit-kick routine. */ +static void __xencons_tx_flush(void); + +static struct tty_driver *xencons_driver; + +/******************** Kernel console driver ********************************/ + +static void kcons_write(struct console *c, const char *s, unsigned int count) +{ + int i = 0; + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + + while (i < count) { + for (; i < count; i++) { + if ((wp - wc) >= (wbuf_size - 1)) + break; + if ((wbuf[WBUF_MASK(wp++)] = s[i]) == '\n') + wbuf[WBUF_MASK(wp++)] = '\r'; + } + + __xencons_tx_flush(); + } + + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static void kcons_write_dom0(struct console *c, const char *s, unsigned int count) +{ + while (count > 0) { + int rc; + rc = HYPERVISOR_console_io(CONSOLEIO_write, count, (char *)s); + if (rc <= 0) + break; + count -= rc; + s += rc; + } +} + +void early_printk(const char *fmt, ...) +{ + va_list args; + int printk_len; + static char printk_buf[1024]; + + /* Emit the output into the temporary buffer */ + va_start(args, fmt); + printk_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args); + va_end(args); + + /* Send the processed output directly to Xen. */ + kcons_write_dom0(NULL, printk_buf, printk_len); +} + +static struct console early_xen_console = { + .name = "earlyxen", + .write = kcons_write_dom0, + .flags = CON_PRINTBUFFER, + .index = -1, +}; + +static int early_console_initialized = 0; + +int __init setup_early_printk(char *opt) +{ + early_console_initialized = 1; + register_console(&early_xen_console); + + return 0; +} + +void __init disable_early_printk(void) +{ + if (!early_console_initialized) + return; + printk("disabling early console\n"); + unregister_console(&early_xen_console); + early_console_initialized = 0; +} + +static struct tty_driver *kcons_device(struct console *c, int *index) +{ + *index = 0; + return xencons_driver; +} + +static struct console kcons_info = { + .name = "xvc", + .device = kcons_device, + .flags = CON_PRINTBUFFER | CON_ENABLED, + .index = -1, +}; + +static int __init xen_console_init(void) +{ + if (!is_running_on_xen()) + goto out; + if (xc_disabled) + goto out; + + if (is_initial_xendomain()) { + kcons_info.write = kcons_write_dom0; + } else { + if (!xen_start_info->console.domU.evtchn) + goto out; + kcons_info.write = kcons_write; + } + if (xc_num == -1) + xc_num = 0; + + wbuf = alloc_bootmem(wbuf_size); + + register_console(&kcons_info); + +out: + return 0; +} +console_initcall(xen_console_init); + +/*** Forcibly flush console data before dying. ***/ +void xencons_force_flush(void) +{ + int sz; + + /* Emergency console is synchronous, so there's nothing to flush. */ + if (!is_running_on_xen() || + is_initial_xendomain() || + !xen_start_info->console.domU.evtchn) + return; + + /* Spin until console data is flushed through to the daemon. */ + while (wc != wp) { + int sent = 0; + if ((sz = wp - wc) == 0) + continue; + sent = xencons_ring_send(&wbuf[WBUF_MASK(wc)], sz); + if (sent > 0) + wc += sent; + } +} + + +/******************** User-space console driver (/dev/console) ************/ + +#define DRV(_d) (_d) + +static struct ktermios *xencons_termios[1]; +static struct ktermios *xencons_termios_locked[1]; +static struct tty_struct *xencons_tty; +static int xencons_priv_irq; +static char x_char; + +void xencons_rx(char *buf, unsigned len) +{ + int i; + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + if (xencons_tty == NULL) + goto out; + + for (i = 0; i < len; i++) { +#ifdef CONFIG_MAGIC_SYSRQ + if (sysrq_on()) { + if (buf[i] == '\x0f') { /* ^O */ + sysrq_requested = jiffies; + continue; /* don't print the sysrq key */ + } else if (sysrq_requested) { + unsigned long sysrq_timeout = + sysrq_requested + HZ*2; + sysrq_requested = 0; + if (time_before(jiffies, sysrq_timeout)) { + spin_unlock_irqrestore( + &xencons_lock, flags); + handle_sysrq( + buf[i], xencons_tty); + spin_lock_irqsave( + &xencons_lock, flags); + continue; + } + } + } +#endif + tty_insert_flip_char(xencons_tty, buf[i], TTY_NORMAL); + } + tty_flip_buffer_push(xencons_tty); + + out: + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static void __xencons_tx_flush(void) +{ + int sent, sz, work_done = 0; + + if (x_char) { + if (is_initial_xendomain()) + kcons_write_dom0(NULL, &x_char, 1); + else + while (x_char) + if (xencons_ring_send(&x_char, 1) == 1) + break; + x_char = 0; + work_done = 1; + } + + while (wc != wp) { + sz = wp - wc; + if (sz > (wbuf_size - WBUF_MASK(wc))) + sz = wbuf_size - WBUF_MASK(wc); + if (is_initial_xendomain()) { + kcons_write_dom0(NULL, &wbuf[WBUF_MASK(wc)], sz); + wc += sz; + } else { + sent = xencons_ring_send(&wbuf[WBUF_MASK(wc)], sz); + if (sent == 0) + break; + wc += sent; + } + work_done = 1; + } + + if (work_done && (xencons_tty != NULL)) { + wake_up_interruptible(&xencons_tty->write_wait); + tty_wakeup(xencons_tty); + } +} + +void xencons_tx(void) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + __xencons_tx_flush(); + spin_unlock_irqrestore(&xencons_lock, flags); +} + +/* Privileged receive callback and transmit kicker. */ +static irqreturn_t xencons_priv_interrupt(int irq, void *dev_id) +{ + static char rbuf[16]; + int l; + + while ((l = HYPERVISOR_console_io(CONSOLEIO_read, 16, rbuf)) > 0) + xencons_rx(rbuf, l); + + xencons_tx(); + + return IRQ_HANDLED; +} + +static int xencons_write_room(struct tty_struct *tty) +{ + return wbuf_size - (wp - wc); +} + +static int xencons_chars_in_buffer(struct tty_struct *tty) +{ + return wp - wc; +} + +static void xencons_send_xchar(struct tty_struct *tty, char ch) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + x_char = ch; + __xencons_tx_flush(); + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static void xencons_throttle(struct tty_struct *tty) +{ + if (I_IXOFF(tty)) + xencons_send_xchar(tty, STOP_CHAR(tty)); +} + +static void xencons_unthrottle(struct tty_struct *tty) +{ + if (I_IXOFF(tty)) { + if (x_char != 0) + x_char = 0; + else + xencons_send_xchar(tty, START_CHAR(tty)); + } +} + +static void xencons_flush_buffer(struct tty_struct *tty) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + wc = wp = 0; + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static inline int __xencons_put_char(unsigned char ch) +{ + if ((wp - wc) == wbuf_size) + return 0; + wbuf[WBUF_MASK(wp++)] = ch; + return 1; +} + +static int xencons_write( + struct tty_struct *tty, + const unsigned char *buf, + int count) +{ + int i; + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + + for (i = 0; i < count; i++) + if (!__xencons_put_char(buf[i])) + break; + + if (i != 0) + __xencons_tx_flush(); + + spin_unlock_irqrestore(&xencons_lock, flags); + + return i; +} + +static void xencons_put_char(struct tty_struct *tty, unsigned char ch) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + (void)__xencons_put_char(ch); + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static void xencons_flush_chars(struct tty_struct *tty) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + __xencons_tx_flush(); + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static void xencons_wait_until_sent(struct tty_struct *tty, int timeout) +{ + unsigned long orig_jiffies = jiffies; + + while (DRV(tty->driver)->chars_in_buffer(tty)) { + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(1); + if (signal_pending(current)) + break; + if (timeout && time_after(jiffies, orig_jiffies + timeout)) + break; + } + + set_current_state(TASK_RUNNING); +} + +static int xencons_open(struct tty_struct *tty, struct file *filp) +{ + unsigned long flags; + + spin_lock_irqsave(&xencons_lock, flags); + tty->driver_data = NULL; + if (xencons_tty == NULL) + xencons_tty = tty; + __xencons_tx_flush(); + spin_unlock_irqrestore(&xencons_lock, flags); + + return 0; +} + +static void xencons_close(struct tty_struct *tty, struct file *filp) +{ + unsigned long flags; + + mutex_lock(&tty_mutex); + + if (tty->count != 1) { + mutex_unlock(&tty_mutex); + return; + } + + /* Prevent other threads from re-opening this tty. */ + set_bit(TTY_CLOSING, &tty->flags); + mutex_unlock(&tty_mutex); + + tty->closing = 1; + tty_wait_until_sent(tty, 0); + if (DRV(tty->driver)->flush_buffer != NULL) + DRV(tty->driver)->flush_buffer(tty); + if (tty->ldisc.flush_buffer != NULL) + tty->ldisc.flush_buffer(tty); + tty->closing = 0; + spin_lock_irqsave(&xencons_lock, flags); + xencons_tty = NULL; + spin_unlock_irqrestore(&xencons_lock, flags); +} + +static struct tty_operations xencons_ops = { + .open = xencons_open, + .close = xencons_close, + .write = xencons_write, + .write_room = xencons_write_room, + .put_char = xencons_put_char, + .flush_chars = xencons_flush_chars, + .chars_in_buffer = xencons_chars_in_buffer, + .send_xchar = xencons_send_xchar, + .flush_buffer = xencons_flush_buffer, + .throttle = xencons_throttle, + .unthrottle = xencons_unthrottle, + .wait_until_sent = xencons_wait_until_sent, +}; + +static int __init xencons_init(void) +{ + int rc; + + if (!is_running_on_xen()) + return -ENODEV; + + if (xc_disabled) + return 0; + + if (!is_initial_xendomain()) { + rc = xencons_ring_init(); + if (rc) + return rc; + } + + xencons_driver = alloc_tty_driver(1); + if (xencons_driver == NULL) + return -ENOMEM; + + DRV(xencons_driver)->name = "xvc"; + DRV(xencons_driver)->major = XEN_XVC_MAJOR; + DRV(xencons_driver)->minor_start = XEN_XVC_MINOR; + DRV(xencons_driver)->name_base = xc_num; + DRV(xencons_driver)->type = TTY_DRIVER_TYPE_SERIAL; + DRV(xencons_driver)->subtype = SERIAL_TYPE_NORMAL; + DRV(xencons_driver)->init_termios = tty_std_termios; + DRV(xencons_driver)->flags = + TTY_DRIVER_REAL_RAW | + TTY_DRIVER_RESET_TERMIOS | + TTY_DRIVER_DYNAMIC_DEV; + DRV(xencons_driver)->termios = xencons_termios; + DRV(xencons_driver)->termios_locked = xencons_termios_locked; + + tty_set_operations(xencons_driver, &xencons_ops); + + if ((rc = tty_register_driver(DRV(xencons_driver))) != 0) { + printk("WARNING: Failed to register Xen virtual " + "console driver as '%s%d'\n", + DRV(xencons_driver)->name, + DRV(xencons_driver)->name_base); + put_tty_driver(xencons_driver); + xencons_driver = NULL; + return rc; + } + + if (is_initial_xendomain()) { + xencons_priv_irq = bind_virq_to_irqhandler( + VIRQ_CONSOLE, + 0, + xencons_priv_interrupt, + 0, + "console", + NULL); + BUG_ON(xencons_priv_irq < 0); + } + + printk("Xen virtual console successfully installed as %s%d\n", + DRV(xencons_driver)->name, xc_num); + + return 0; +} + +module_init(xencons_init); =================================================================== --- /dev/null +++ b/drivers/xen/console/xencons_ring.c @@ -0,0 +1,144 @@ +/* + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 + * as published by the Free Software Foundation; or, when distributed + * separately from the Linux kernel or incorporated into other + * software packages, subject to the following license: + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this source file (the "Software"), to deal in the Software without + * restriction, including without limitation the rights to use, copy, modify, + * merge, publish, distribute, sublicense, and/or sell copies of the Software, + * and to permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static int xencons_irq; + +static inline struct xencons_interface *xencons_interface(void) +{ + return mfn_to_virt(xen_start_info->console.domU.mfn); +} + +static inline void notify_daemon(void) +{ + /* Use evtchn: this is called early, before irq is set up. */ + notify_remote_via_evtchn(xen_start_info->console.domU.evtchn); +} + +int xencons_ring_send(const char *data, unsigned len) +{ + int sent = 0; + struct xencons_interface *intf = xencons_interface(); + XENCONS_RING_IDX cons, prod; + + cons = intf->out_cons; + prod = intf->out_prod; + mb(); + BUG_ON((prod - cons) > sizeof(intf->out)); + + while ((sent < len) && ((prod - cons) < sizeof(intf->out))) + intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++]; + + wmb(); + intf->out_prod = prod; + + notify_daemon(); + + return sent; +} + +static irqreturn_t handle_input(int irq, void *unused) +{ + struct xencons_interface *intf = xencons_interface(); + XENCONS_RING_IDX cons, prod; + + cons = intf->in_cons; + prod = intf->in_prod; + mb(); + BUG_ON((prod - cons) > sizeof(intf->in)); + + while (cons != prod) { + xencons_rx(intf->in+MASK_XENCONS_IDX(cons,intf->in), 1); + cons++; + } + + mb(); + intf->in_cons = cons; + + notify_daemon(); + + xencons_tx(); + + return IRQ_HANDLED; +} + +int xencons_ring_init(void) +{ + int irq; + + if (xencons_irq) + unbind_from_irqhandler(xencons_irq, NULL); + xencons_irq = 0; + + if (!is_running_on_xen() || + is_initial_xendomain() || + !xen_start_info->console.domU.evtchn) + return -ENODEV; + + irq = bind_evtchn_to_irqhandler( + xen_start_info->console.domU.evtchn, + handle_input, 0, "xencons", NULL); + if (irq < 0) { + printk(KERN_ERR "XEN console request irq failed %i\n", irq); + return irq; + } + + xencons_irq = irq; + + /* In case we have in-flight data after save/restore... */ + notify_daemon(); + + return 0; +} + +void xencons_resume(void) +{ + (void)xencons_ring_init(); +} =================================================================== --- /dev/null +++ b/include/xen/xencons.h @@ -0,0 +1,14 @@ +#ifndef __ASM_XENCONS_H__ +#define __ASM_XENCONS_H__ + +void xencons_force_flush(void); +void xencons_resume(void); + +/* Interrupt work hooks. Receive data, or kick data out. */ +void xencons_rx(char *buf, unsigned len); +void xencons_tx(void); + +int xencons_ring_init(void); +int xencons_ring_send(const char *data, unsigned len); + +#endif /* __ASM_XENCONS_H__ */ =================================================================== --- a/init/main.c +++ b/init/main.c @@ -495,6 +495,8 @@ asmlinkage void __init start_kernel(void unwind_init(); lockdep_init(); + //setup_early_printk(NULL); + local_irq_disable(); early_boot_irqs_off(); early_init_irq_lock_class(); --