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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [kernel/] [printk.c] - Rev 1275
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/* * linux/kernel/printk.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Modified to make sys_syslog() more flexible: added commands to * return the last 4k of kernel messages, regardless of whether * they've been read or not. Added option to suppress kernel printk's * to the console. Added hook for sending the console messages * elsewhere, in preparation for a serial line console (someday). * Ted Ts'o, 2/11/93. * Modified for sysctl support, 1/8/97, Chris Horn. * Fixed SMP synchronization, 08/08/99, Manfred Spraul * manfreds@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton <andrewm@uow.edu.au> */ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/smp_lock.h> #include <linux/console.h> #include <linux/init.h> #include <linux/module.h> #include <linux/interrupt.h> /* For in_interrupt() */ #include <linux/config.h> #include <asm/uaccess.h> #if !defined(CONFIG_LOG_BUF_SHIFT) || (CONFIG_LOG_BUF_SHIFT == 0) #if defined(CONFIG_MULTIQUAD) || defined(CONFIG_IA64) #define LOG_BUF_LEN (65536) #elif defined(CONFIG_ARCH_S390) #define LOG_BUF_LEN (131072) #elif defined(CONFIG_SMP) #define LOG_BUF_LEN (32768) #else #define LOG_BUF_LEN (16384) /* This must be a power of two */ #endif #else /* CONFIG_LOG_BUF_SHIFT */ #define LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) #endif #define LOG_BUF_MASK (LOG_BUF_LEN-1) #ifndef arch_consoles_callable #define arch_consoles_callable() (1) #endif /* printk's without a loglevel use this.. */ #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ /* We show everything that is MORE important than this.. */ #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */ #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ DECLARE_WAIT_QUEUE_HEAD(log_wait); int console_printk[4] = { DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */ }; int oops_in_progress; /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */ static DECLARE_MUTEX(console_sem); struct console *console_drivers; /* * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars * It is also used in interesting ways to provide interlocking in * release_console_sem(). */ static spinlock_t logbuf_lock = SPIN_LOCK_UNLOCKED; static char log_buf[LOG_BUF_LEN]; #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) /* * The indices into log_buf are not constrained to LOG_BUF_LEN - they * must be masked before subscripting */ static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */ static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */ static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; static int preferred_console = -1; /* Flag: console code may call schedule() */ static int console_may_schedule; /* * Setup a list of consoles. Called from init/main.c */ static int __init console_setup(char *str) { struct console_cmdline *c; char name[sizeof(c->name)]; char *s, *options; int i, idx; /* * Decode str into name, index, options. */ if (str[0] >= '0' && str[0] <= '9') { strcpy(name, "ttyS"); strncpy(name + 4, str, sizeof(name) - 5); } else strncpy(name, str, sizeof(name) - 1); name[sizeof(name) - 1] = 0; if ((options = strchr(str, ',')) != NULL) *(options++) = 0; #ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(name, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(name, "ttyS1"); #endif for(s = name; *s; s++) if (*s >= '0' && *s <= '9') break; idx = simple_strtoul(s, NULL, 10); *s = 0; /* * See if this tty is not yet registered, and * if we have a slot free. */ for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) if (strcmp(console_cmdline[i].name, name) == 0 && console_cmdline[i].index == idx) { preferred_console = i; return 1; } if (i == MAX_CMDLINECONSOLES) return 1; preferred_console = i; c = &console_cmdline[i]; memcpy(c->name, name, sizeof(c->name)); c->options = options; c->index = idx; return 1; } __setup("console=", console_setup); /* * Commands to do_syslog: * * 0 -- Close the log. Currently a NOP. * 1 -- Open the log. Currently a NOP. * 2 -- Read from the log. * 3 -- Read all messages remaining in the ring buffer. * 4 -- Read and clear all messages remaining in the ring buffer * 5 -- Clear ring buffer. * 6 -- Disable printk's to console * 7 -- Enable printk's to console * 8 -- Set level of messages printed to console * 9 -- Return number of unread characters in the log buffer */ int do_syslog(int type, char * buf, int len) { unsigned long i, j, limit, count; int do_clear = 0; char c; int error = 0; switch (type) { case 0: /* Close log */ break; case 1: /* Open log */ break; case 2: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; error = verify_area(VERIFY_WRITE,buf,len); if (error) goto out; error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; spin_lock_irq(&logbuf_lock); while ((log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; spin_unlock_irq(&logbuf_lock); __put_user(c,buf); buf++; i++; spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); error = i; break; case 4: /* Read/clear last kernel messages */ do_clear = 1; /* FALL THRU */ case 3: /* Read last kernel messages */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; error = verify_area(VERIFY_WRITE,buf,len); if (error) goto out; count = len; if (count > LOG_BUF_LEN) count = LOG_BUF_LEN; spin_lock_irq(&logbuf_lock); if (count > logged_chars) count = logged_chars; if (do_clear) logged_chars = 0; limit = log_end; /* * __put_user() could sleep, and while we sleep * printk() could overwrite the messages * we try to copy to user space. Therefore * the messages are copied in reverse. <manfreds> */ for(i=0;i < count;i++) { j = limit-1-i; if (j+LOG_BUF_LEN < log_end) break; c = LOG_BUF(j); spin_unlock_irq(&logbuf_lock); __put_user(c,&buf[count-1-i]); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); error = i; if(i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for(i=0;i<error;i++) { __get_user(c,&buf[i+offset]); __put_user(c,&buf[i]); } } break; case 5: /* Clear ring buffer */ spin_lock_irq(&logbuf_lock); logged_chars = 0; spin_unlock_irq(&logbuf_lock); break; case 6: /* Disable logging to console */ spin_lock_irq(&logbuf_lock); console_loglevel = minimum_console_loglevel; spin_unlock_irq(&logbuf_lock); break; case 7: /* Enable logging to console */ spin_lock_irq(&logbuf_lock); console_loglevel = default_console_loglevel; spin_unlock_irq(&logbuf_lock); break; case 8: /* Set level of messages printed to console */ error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; spin_lock_irq(&logbuf_lock); console_loglevel = len; spin_unlock_irq(&logbuf_lock); error = 0; break; case 9: /* Number of chars in the log buffer */ spin_lock_irq(&logbuf_lock); error = log_end - log_start; spin_unlock_irq(&logbuf_lock); break; default: error = -EINVAL; break; } out: return error; } asmlinkage long sys_syslog(int type, char * buf, int len) { if ((type != 3) && !capable(CAP_SYS_ADMIN)) return -EPERM; return do_syslog(type, buf, len); } /* * Call the console drivers on a range of log_buf */ static void __call_console_drivers(unsigned long start, unsigned long end) { struct console *con; for (con = console_drivers; con; con = con->next) { if ((con->flags & CON_ENABLED) && con->write) con->write(con, &LOG_BUF(start), end - start); } } /* * Write out chars from start to end - 1 inclusive */ static void _call_console_drivers(unsigned long start, unsigned long end, int msg_log_level) { if (msg_log_level < console_loglevel && console_drivers && start != end) { if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { /* wrapped write */ __call_console_drivers(start & LOG_BUF_MASK, LOG_BUF_LEN); __call_console_drivers(0, end & LOG_BUF_MASK); } else { __call_console_drivers(start, end); } } } /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_sem must be held. */ static void call_console_drivers(unsigned long start, unsigned long end) { unsigned long cur_index, start_print; static int msg_level = -1; if (((long)(start - end)) > 0) BUG(); cur_index = start; start_print = start; while (cur_index != end) { if ( msg_level < 0 && ((end - cur_index) > 2) && LOG_BUF(cur_index + 0) == '<' && LOG_BUF(cur_index + 1) >= '0' && LOG_BUF(cur_index + 1) <= '7' && LOG_BUF(cur_index + 2) == '>') { msg_level = LOG_BUF(cur_index + 1) - '0'; cur_index += 3; start_print = cur_index; } while (cur_index != end) { char c = LOG_BUF(cur_index); cur_index++; if (c == '\n') { if (msg_level < 0) { /* * printk() has already given us loglevel tags in * the buffer. This code is here in case the * log buffer has wrapped right round and scribbled * on those tags */ msg_level = default_message_loglevel; } _call_console_drivers(start_print, cur_index, msg_level); msg_level = -1; start_print = cur_index; break; } } } _call_console_drivers(start_print, end, msg_level); } static void emit_log_char(char c) { LOG_BUF(log_end) = c; log_end++; if (log_end - log_start > LOG_BUF_LEN) log_start = log_end - LOG_BUF_LEN; if (log_end - con_start > LOG_BUF_LEN) con_start = log_end - LOG_BUF_LEN; if (logged_chars < LOG_BUF_LEN) logged_chars++; } /* * This is printk. It can be called from any context. We want it to work. * * We try to grab the console_sem. If we succeed, it's easy - we log the output and * call the console drivers. If we fail to get the semaphore we place the output * into the log buffer and return. The current holder of the console_sem will * notice the new output in release_console_sem() and will send it to the * consoles before releasing the semaphore. * * One effect of this deferred printing is that code which calls printk() and * then changes console_loglevel may break. This is because console_loglevel * is inspected when the actual printing occurs. */ asmlinkage int printk(const char *fmt, ...) { va_list args; unsigned long flags; int printed_len; char *p; static char printk_buf[1024]; static int log_level_unknown = 1; if (oops_in_progress) { /* If a crash is occurring, make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem); } /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); /* Emit the output into the temporary buffer */ va_start(args, fmt); printed_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args); va_end(args); /* * Copy the output into log_buf. If the caller didn't provide * appropriate log level tags, we insert them here */ for (p = printk_buf; *p; p++) { if (log_level_unknown) { if (p[0] != '<' || p[1] < '0' || p[1] > '7' || p[2] != '>') { emit_log_char('<'); emit_log_char(default_message_loglevel + '0'); emit_log_char('>'); } log_level_unknown = 0; } emit_log_char(*p); if (*p == '\n') log_level_unknown = 1; } if (!arch_consoles_callable()) { /* * On some architectures, the consoles are not usable * on secondary CPUs early in the boot process. */ spin_unlock_irqrestore(&logbuf_lock, flags); goto out; } if (!down_trylock(&console_sem)) { /* * We own the drivers. We can drop the spinlock and let * release_console_sem() print the text */ spin_unlock_irqrestore(&logbuf_lock, flags); console_may_schedule = 0; release_console_sem(); } else { /* * Someone else owns the drivers. We drop the spinlock, which * allows the semaphore holder to proceed and to call the * console drivers with the output which we just produced. */ spin_unlock_irqrestore(&logbuf_lock, flags); } out: return printed_len; } EXPORT_SYMBOL(printk); /** * acquire_console_sem - lock the console system for exclusive use. * * Acquires a semaphore which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * Can sleep, returns nothing. */ void acquire_console_sem(void) { if (in_interrupt()) BUG(); down(&console_sem); console_may_schedule = 1; } EXPORT_SYMBOL(acquire_console_sem); /** * release_console_sem - unlock the console system * * Releases the semaphore which the caller holds on the console system * and the console driver list. * * While the semaphore was held, console output may have been buffered * by printk(). If this is the case, release_console_sem() emits * the output prior to releasing the semaphore. * * If there is output waiting for klogd, we wake it up. * * release_console_sem() may be called from any context. */ void release_console_sem(void) { unsigned long flags; unsigned long _con_start, _log_end; unsigned long must_wake_klogd = 0; for ( ; ; ) { spin_lock_irqsave(&logbuf_lock, flags); must_wake_klogd |= log_start - log_end; if (con_start == log_end) break; /* Nothing to print */ _con_start = con_start; _log_end = log_end; con_start = log_end; /* Flush */ spin_unlock_irqrestore(&logbuf_lock, flags); call_console_drivers(_con_start, _log_end); } console_may_schedule = 0; up(&console_sem); spin_unlock_irqrestore(&logbuf_lock, flags); if (must_wake_klogd && !oops_in_progress) wake_up_interruptible(&log_wait); } /** console_conditional_schedule - yield the CPU if required * * If the console code is currently allowed to sleep, and * if this CPU should yield the CPU to another task, do * so here. * * Must be called within acquire_console_sem(). */ void console_conditional_schedule(void) { if (console_may_schedule && current->need_resched) { set_current_state(TASK_RUNNING); schedule(); } } void console_print(const char *s) { printk(KERN_EMERG "%s", s); } EXPORT_SYMBOL(console_print); void console_unblank(void) { struct console *c; /* * Try to get the console semaphore. If someone else owns it * we have to return without unblanking because console_unblank * may be called in interrupt context. */ if (down_trylock(&console_sem) != 0) return; console_may_schedule = 0; for (c = console_drivers; c != NULL; c = c->next) if ((c->flags & CON_ENABLED) && c->unblank) c->unblank(); release_console_sem(); } EXPORT_SYMBOL(console_unblank); /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to * print any messages that were printed by the kernel before the * console driver was initialized. */ void register_console(struct console * console) { int i; unsigned long flags; /* * See if we want to use this console driver. If we * didn't select a console we take the first one * that registers here. */ if (preferred_console < 0) { if (console->index < 0) console->index = 0; if (console->setup == NULL || console->setup(console, NULL) == 0) { console->flags |= CON_ENABLED | CON_CONSDEV; preferred_console = 0; } } /* * See if this console matches one we selected on * the command line. */ for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) { if (strcmp(console_cmdline[i].name, console->name) != 0) continue; if (console->index >= 0 && console->index != console_cmdline[i].index) continue; if (console->index < 0) console->index = console_cmdline[i].index; if (console->setup && console->setup(console, console_cmdline[i].options) != 0) break; console->flags |= CON_ENABLED; console->index = console_cmdline[i].index; if (i == preferred_console) console->flags |= CON_CONSDEV; break; } if (!(console->flags & CON_ENABLED)) return; /* * Put this console in the list - keep the * preferred driver at the head of the list. */ acquire_console_sem(); if ((console->flags & CON_CONSDEV) || console_drivers == NULL) { console->next = console_drivers; console_drivers = console; } else { console->next = console_drivers->next; console_drivers->next = console; } if (console->flags & CON_PRINTBUFFER) { /* * release_console_sem() will print out the buffered messages for us. */ spin_lock_irqsave(&logbuf_lock, flags); con_start = log_start; spin_unlock_irqrestore(&logbuf_lock, flags); } release_console_sem(); } EXPORT_SYMBOL(register_console); int unregister_console(struct console * console) { struct console *a,*b; int res = 1; acquire_console_sem(); if (console_drivers == console) { console_drivers=console->next; res = 0; } else { for (a=console_drivers->next, b=console_drivers ; a; b=a, a=b->next) { if (a == console) { b->next = a->next; res = 0; break; } } } /* If last console is removed, we re-enable picking the first * one that gets registered. Without that, pmac early boot console * would prevent fbcon from taking over. */ if (console_drivers == NULL) preferred_console = -1; release_console_sem(); return res; } EXPORT_SYMBOL(unregister_console); /** * tty_write_message - write a message to a certain tty, not just the console. * * This is used for messages that need to be redirected to a specific tty. * We don't put it into the syslog queue right now maybe in the future if * really needed. */ void tty_write_message(struct tty_struct *tty, char *msg) { if (tty && tty->driver.write) tty->driver.write(tty, 0, msg, strlen(msg)); return; }
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