/* * 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 * manfred@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton */ #include <linux/kernel.h>#include <linux/mm.h>#include <linux/tty.h>#include <linux/tty_driver.h>#include <linux/console.h>#include <linux/init.h>#include <linux/jiffies.h>#include <linux/nmi.h>#include <linux/module.h>#include <linux/moduleparam.h>#include <linux/interrupt.h> /* For in_interrupt() */#include <linux/delay.h>#include <linux/smp.h>#include <linux/security.h>#include <linux/bootmem.h>#include <linux/memblock.h>#include <linux/syscalls.h>#include <linux/kexec.h>#include <linux/kdb.h>#include <linux/ratelimit.h>#include <linux/kmsg_dump.h>#include <linux/syslog.h>#include <linux/cpu.h>#include <linux/notifier.h>#include <linux/rculist.h> #include <asm/uaccess.h> /* * Architectures can override it: */void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...){} #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) /* printk's without a loglevel use this.. */#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL /* 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 */}; /* * Low level drivers may need that to know if they can schedule in * their unblank() callback or not. So let's export it. */int oops_in_progress;EXPORT_SYMBOL(oops_in_progress); /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */static DEFINE_SEMAPHORE(console_sem);struct console *console_drivers;EXPORT_SYMBOL_GPL(console_drivers); /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's * definitely not the perfect debug tool (we don't know if _WE_ * hold it are racing, but it helps tracking those weird code * path in the console code where we end up in places I want * locked without the console sempahore held */static int console_locked, console_suspended; /* * 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 * console_unlock();. */static DEFINE_RAW_SPINLOCK(logbuf_lock); #define LOG_BUF_MASK (log_buf_len-1)#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 log_start; /* Index into log_buf: next char to be read by syslog() */static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */ /* * If exclusive_console is non-NULL then only this console is to be printed to. */static struct console *exclusive_console; /* * Array of consoles built from command line options (console=) */struct console_cmdline{ char name[8]; /* Name of the driver */ int index; /* Minor dev. to use */ char *options; /* Options for the driver */#ifdef CONFIG_A11Y_BRAILLE_CONSOLE char *brl_options; /* Options for braille driver */#endif}; #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];static int selected_console = -1;static int preferred_console = -1;int console_set_on_cmdline;EXPORT_SYMBOL(console_set_on_cmdline); /* Flag: console code may call schedule() */static int console_may_schedule; #ifdef CONFIG_PRINTK static char __log_buf[__LOG_BUF_LEN];static char *log_buf = __log_buf;static int log_buf_len = __LOG_BUF_LEN;static unsigned logged_chars; /* Number of chars produced since last read+clear operation */static int saved_console_loglevel = -1; #ifdef CONFIG_KEXEC/* * This appends the listed symbols to /proc/vmcoreinfo * * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to * obtain access to symbols that are otherwise very difficult to locate. These * symbols are specifically used so that utilities can access and extract the * dmesg log from a vmcore file after a crash. */void log_buf_kexec_setup(void){ VMCOREINFO_SYMBOL(log_buf); VMCOREINFO_SYMBOL(log_end); VMCOREINFO_SYMBOL(log_buf_len); VMCOREINFO_SYMBOL(logged_chars);}#endif /* requested log_buf_len from kernel cmdline */static unsigned long __initdata new_log_buf_len; /* save requested log_buf_len since it's too early to process it */static int __init log_buf_len_setup(char *str){ unsigned size = memparse(str, &str); if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) new_log_buf_len = size; return 0;}early_param("log_buf_len", log_buf_len_setup); void __init setup_log_buf(int early){ unsigned long flags; unsigned start, dest_idx, offset; char *new_log_buf; int free; if (!new_log_buf_len) return; if (early) { unsigned long mem; mem = memblock_alloc(new_log_buf_len, PAGE_SIZE); if (mem == MEMBLOCK_ERROR) return; new_log_buf = __va(mem); } else { new_log_buf = alloc_bootmem_nopanic(new_log_buf_len); } if (unlikely(!new_log_buf)) { pr_err("log_buf_len: %ld bytes not available\n", new_log_buf_len); return; } raw_spin_lock_irqsave(&logbuf_lock, flags); log_buf_len = new_log_buf_len; log_buf = new_log_buf; new_log_buf_len = 0; free = __LOG_BUF_LEN - log_end; offset = start = min(con_start, log_start); dest_idx = 0; while (start != log_end) { unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1); log_buf[dest_idx] = __log_buf[log_idx_mask]; start++; dest_idx++; } log_start -= offset; con_start -= offset; log_end -= offset; raw_spin_unlock_irqrestore(&logbuf_lock, flags); pr_info("log_buf_len: %d\n", log_buf_len); pr_info("early log buf free: %d(%d%%)\n", free, (free * 100) / __LOG_BUF_LEN);} #ifdef CONFIG_BOOT_PRINTK_DELAY static int boot_delay; /* msecs delay after each printk during bootup */static unsigned long long loops_per_msec; /* based on boot_delay */ static int __init boot_delay_setup(char *str){ unsigned long lpj; lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ loops_per_msec = (unsigned long long)lpj / 1000 * HZ; get_option(&str, &boot_delay); if (boot_delay > 10 * 1000) boot_delay = 0; pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " "HZ: %d, loops_per_msec: %llu\n", boot_delay, preset_lpj, lpj, HZ, loops_per_msec); return 1;}__setup("boot_delay=", boot_delay_setup); static void boot_delay_msec(void){ unsigned long long k; unsigned long timeout; if (boot_delay == 0 || system_state != SYSTEM_BOOTING) return; k = (unsigned long long)loops_per_msec * boot_delay; timeout = jiffies + msecs_to_jiffies(boot_delay); while (k) { k--; cpu_relax(); /* * use (volatile) jiffies to prevent * compiler reduction; loop termination via jiffies * is secondary and may or may not happen. */ if (time_after(jiffies, timeout)) break; touch_nmi_watchdog(); }}#elsestatic inline void boot_delay_msec(void){}#endif #ifdef CONFIG_SECURITY_DMESG_RESTRICTint dmesg_restrict = 1;#elseint dmesg_restrict;#endif static int syslog_action_restricted(int type){ if (dmesg_restrict) return 1; /* Unless restricted, we allow "read all" and "get buffer size" for everybody */ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;} static int check_syslog_permissions(int type, bool from_file){ /* * If this is from /proc/kmsg and we've already opened it, then we've * already done the capabilities checks at open time. */ if (from_file && type != SYSLOG_ACTION_OPEN) return 0; if (syslog_action_restricted(type)) { if (capable(CAP_SYSLOG)) return 0; /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ if (capable(CAP_SYS_ADMIN)) { printk_once(KERN_WARNING "%s (%d): " "Attempt to access syslog with CAP_SYS_ADMIN " "but no CAP_SYSLOG (deprecated).\n", current->comm, task_pid_nr(current)); return 0; } return -EPERM; } return 0;} int do_syslog(int type, char __user *buf, int len, bool from_file){ unsigned i, j, limit, count; int do_clear = 0; char c; int error; error = check_syslog_permissions(type, from_file); if (error) goto out; error = security_syslog(type); if (error) return error; switch (type) { case SYSLOG_ACTION_CLOSE: /* Close log */ break; case SYSLOG_ACTION_OPEN: /* Open log */ break; case SYSLOG_ACTION_READ: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; raw_spin_lock_irq(&logbuf_lock); while (!error && (log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; raw_spin_unlock_irq(&logbuf_lock); error = __put_user(c,buf); buf++; i++; cond_resched(); raw_spin_lock_irq(&logbuf_lock); } raw_spin_unlock_irq(&logbuf_lock); if (!error) error = i; break; /* Read/clear last kernel messages */ case SYSLOG_ACTION_READ_CLEAR: do_clear = 1; /* FALL THRU */ /* Read last kernel messages */ case SYSLOG_ACTION_READ_ALL: error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } count = len; if (count > log_buf_len) count = log_buf_len; raw_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 && !error; i++) { j = limit-1-i; if (j + log_buf_len < log_end) break; c = LOG_BUF(j); raw_spin_unlock_irq(&logbuf_lock); error = __put_user(c,&buf[count-1-i]); cond_resched(); raw_spin_lock_irq(&logbuf_lock); } raw_spin_unlock_irq(&logbuf_lock); if (error) break; error = i; if (i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for (i = 0; i < error; i++) { if (__get_user(c,&buf[i+offset]) || __put_user(c,&buf[i])) { error = -EFAULT; break; } cond_resched(); } } break; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: logged_chars = 0; break; /* Disable logging to console */ case SYSLOG_ACTION_CONSOLE_OFF: if (saved_console_loglevel == -1) saved_console_loglevel = console_loglevel; console_loglevel = minimum_console_loglevel; break; /* Enable logging to console */ case SYSLOG_ACTION_CONSOLE_ON: if (saved_console_loglevel != -1) { console_loglevel = saved_console_loglevel; saved_console_loglevel = -1; } break; /* Set level of messages printed to console */ case SYSLOG_ACTION_CONSOLE_LEVEL: error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; /* Implicitly re-enable logging to console */ saved_console_loglevel = -1; error = 0; break; /* Number of chars in the log buffer */ case SYSLOG_ACTION_SIZE_UNREAD: error = log_end - log_start; break; /* Size of the log buffer */ case SYSLOG_ACTION_SIZE_BUFFER: error = log_buf_len; break; default: error = -EINVAL; break; }out: return error;} SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len){ return do_syslog(type, buf, len, SYSLOG_FROM_CALL);} #ifdef CONFIG_KGDB_KDB/* kdb dmesg command needs access to the syslog buffer. do_syslog() * uses locks so it cannot be used during debugging. Just tell kdb * where the start and end of the physical and logical logs are. This * is equivalent to do_syslog(3). */void kdb_syslog_data(char *syslog_data[4]){ syslog_data[0] = log_buf; syslog_data[1] = log_buf + log_buf_len;Lines 1–500 of 1763. Load more
/* * 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 * manfred@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton */ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/console.h> #include <linux/init.h> #include <linux/jiffies.h> #include <linux/nmi.h> #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/interrupt.h> /* For in_interrupt() */ #include <linux/delay.h> #include <linux/smp.h> #include <linux/security.h> #include <linux/bootmem.h> #include <linux/memblock.h> #include <linux/syscalls.h> #include <linux/kexec.h> #include <linux/kdb.h> #include <linux/ratelimit.h> #include <linux/kmsg_dump.h> #include <linux/syslog.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/rculist.h> #include <asm/uaccess.h> /* * Architectures can override it: */ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...) { } #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) /* printk's without a loglevel use this.. */ #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL /* 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 */ }; /* * Low level drivers may need that to know if they can schedule in * their unblank() callback or not. So let's export it. */ int oops_in_progress; EXPORT_SYMBOL(oops_in_progress); /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */ static DEFINE_SEMAPHORE(console_sem); struct console *console_drivers; EXPORT_SYMBOL_GPL(console_drivers); /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's * definitely not the perfect debug tool (we don't know if _WE_ * hold it are racing, but it helps tracking those weird code * path in the console code where we end up in places I want * locked without the console sempahore held */ static int console_locked, console_suspended; /* * 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 * console_unlock();. */ static DEFINE_RAW_SPINLOCK(logbuf_lock); #define LOG_BUF_MASK (log_buf_len-1) #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 log_start; /* Index into log_buf: next char to be read by syslog() */ static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */ static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */ /* * If exclusive_console is non-NULL then only this console is to be printed to. */ static struct console *exclusive_console; /* * Array of consoles built from command line options (console=) */ struct console_cmdline { char name[8]; /* Name of the driver */ int index; /* Minor dev. to use */ char *options; /* Options for the driver */ #ifdef CONFIG_A11Y_BRAILLE_CONSOLE char *brl_options; /* Options for braille driver */ #endif }; #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; static int selected_console = -1; static int preferred_console = -1; int console_set_on_cmdline; EXPORT_SYMBOL(console_set_on_cmdline); /* Flag: console code may call schedule() */ static int console_may_schedule; #ifdef CONFIG_PRINTK static char __log_buf[__LOG_BUF_LEN]; static char *log_buf = __log_buf; static int log_buf_len = __LOG_BUF_LEN; static unsigned logged_chars; /* Number of chars produced since last read+clear operation */ static int saved_console_loglevel = -1; #ifdef CONFIG_KEXEC /* * This appends the listed symbols to /proc/vmcoreinfo * * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to * obtain access to symbols that are otherwise very difficult to locate. These * symbols are specifically used so that utilities can access and extract the * dmesg log from a vmcore file after a crash. */ void log_buf_kexec_setup(void) { VMCOREINFO_SYMBOL(log_buf); VMCOREINFO_SYMBOL(log_end); VMCOREINFO_SYMBOL(log_buf_len); VMCOREINFO_SYMBOL(logged_chars); } #endif /* requested log_buf_len from kernel cmdline */ static unsigned long __initdata new_log_buf_len; /* save requested log_buf_len since it's too early to process it */ static int __init log_buf_len_setup(char *str) { unsigned size = memparse(str, &str); if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) new_log_buf_len = size; return 0; } early_param("log_buf_len", log_buf_len_setup); void __init setup_log_buf(int early) { unsigned long flags; unsigned start, dest_idx, offset; char *new_log_buf; int free; if (!new_log_buf_len) return; if (early) { unsigned long mem; mem = memblock_alloc(new_log_buf_len, PAGE_SIZE); if (mem == MEMBLOCK_ERROR) return; new_log_buf = __va(mem); } else { new_log_buf = alloc_bootmem_nopanic(new_log_buf_len); } if (unlikely(!new_log_buf)) { pr_err("log_buf_len: %ld bytes not available\n", new_log_buf_len); return; } raw_spin_lock_irqsave(&logbuf_lock, flags); log_buf_len = new_log_buf_len; log_buf = new_log_buf; new_log_buf_len = 0; free = __LOG_BUF_LEN - log_end; offset = start = min(con_start, log_start); dest_idx = 0; while (start != log_end) { unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1); log_buf[dest_idx] = __log_buf[log_idx_mask]; start++; dest_idx++; } log_start -= offset; con_start -= offset; log_end -= offset; raw_spin_unlock_irqrestore(&logbuf_lock, flags); pr_info("log_buf_len: %d\n", log_buf_len); pr_info("early log buf free: %d(%d%%)\n", free, (free * 100) / __LOG_BUF_LEN); } #ifdef CONFIG_BOOT_PRINTK_DELAY static int boot_delay; /* msecs delay after each printk during bootup */ static unsigned long long loops_per_msec; /* based on boot_delay */ static int __init boot_delay_setup(char *str) { unsigned long lpj; lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ loops_per_msec = (unsigned long long)lpj / 1000 * HZ; get_option(&str, &boot_delay); if (boot_delay > 10 * 1000) boot_delay = 0; pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " "HZ: %d, loops_per_msec: %llu\n", boot_delay, preset_lpj, lpj, HZ, loops_per_msec); return 1; } __setup("boot_delay=", boot_delay_setup); static void boot_delay_msec(void) { unsigned long long k; unsigned long timeout; if (boot_delay == 0 || system_state != SYSTEM_BOOTING) return; k = (unsigned long long)loops_per_msec * boot_delay; timeout = jiffies + msecs_to_jiffies(boot_delay); while (k) { k--; cpu_relax(); /* * use (volatile) jiffies to prevent * compiler reduction; loop termination via jiffies * is secondary and may or may not happen. */ if (time_after(jiffies, timeout)) break; touch_nmi_watchdog(); } } #else static inline void boot_delay_msec(void) { } #endif #ifdef CONFIG_SECURITY_DMESG_RESTRICT int dmesg_restrict = 1; #else int dmesg_restrict; #endif static int syslog_action_restricted(int type) { if (dmesg_restrict) return 1; /* Unless restricted, we allow "read all" and "get buffer size" for everybody */ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER; } static int check_syslog_permissions(int type, bool from_file) { /* * If this is from /proc/kmsg and we've already opened it, then we've * already done the capabilities checks at open time. */ if (from_file && type != SYSLOG_ACTION_OPEN) return 0; if (syslog_action_restricted(type)) { if (capable(CAP_SYSLOG)) return 0; /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ if (capable(CAP_SYS_ADMIN)) { printk_once(KERN_WARNING "%s (%d): " "Attempt to access syslog with CAP_SYS_ADMIN " "but no CAP_SYSLOG (deprecated).\n", current->comm, task_pid_nr(current)); return 0; } return -EPERM; } return 0; } int do_syslog(int type, char __user *buf, int len, bool from_file) { unsigned i, j, limit, count; int do_clear = 0; char c; int error; error = check_syslog_permissions(type, from_file); if (error) goto out; error = security_syslog(type); if (error) return error; switch (type) { case SYSLOG_ACTION_CLOSE: /* Close log */ break; case SYSLOG_ACTION_OPEN: /* Open log */ break; case SYSLOG_ACTION_READ: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; raw_spin_lock_irq(&logbuf_lock); while (!error && (log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; raw_spin_unlock_irq(&logbuf_lock); error = __put_user(c,buf); buf++; i++; cond_resched(); raw_spin_lock_irq(&logbuf_lock); } raw_spin_unlock_irq(&logbuf_lock); if (!error) error = i; break; /* Read/clear last kernel messages */ case SYSLOG_ACTION_READ_CLEAR: do_clear = 1; /* FALL THRU */ /* Read last kernel messages */ case SYSLOG_ACTION_READ_ALL: error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; if (!access_ok(VERIFY_WRITE, buf, len)) { error = -EFAULT; goto out; } count = len; if (count > log_buf_len) count = log_buf_len; raw_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 && !error; i++) { j = limit-1-i; if (j + log_buf_len < log_end) break; c = LOG_BUF(j); raw_spin_unlock_irq(&logbuf_lock); error = __put_user(c,&buf[count-1-i]); cond_resched(); raw_spin_lock_irq(&logbuf_lock); } raw_spin_unlock_irq(&logbuf_lock); if (error) break; error = i; if (i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for (i = 0; i < error; i++) { if (__get_user(c,&buf[i+offset]) || __put_user(c,&buf[i])) { error = -EFAULT; break; } cond_resched(); } } break; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: logged_chars = 0; break; /* Disable logging to console */ case SYSLOG_ACTION_CONSOLE_OFF: if (saved_console_loglevel == -1) saved_console_loglevel = console_loglevel; console_loglevel = minimum_console_loglevel; break; /* Enable logging to console */ case SYSLOG_ACTION_CONSOLE_ON: if (saved_console_loglevel != -1) { console_loglevel = saved_console_loglevel; saved_console_loglevel = -1; } break; /* Set level of messages printed to console */ case SYSLOG_ACTION_CONSOLE_LEVEL: error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; /* Implicitly re-enable logging to console */ saved_console_loglevel = -1; error = 0; break; /* Number of chars in the log buffer */ case SYSLOG_ACTION_SIZE_UNREAD: error = log_end - log_start; break; /* Size of the log buffer */ case SYSLOG_ACTION_SIZE_BUFFER: error = log_buf_len; break; default: error = -EINVAL; break; } out: return error; } SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) { return do_syslog(type, buf, len, SYSLOG_FROM_CALL); } #ifdef CONFIG_KGDB_KDB /* kdb dmesg command needs access to the syslog buffer. do_syslog() * uses locks so it cannot be used during debugging. Just tell kdb * where the start and end of the physical and logical logs are. This * is equivalent to do_syslog(3). */ void kdb_syslog_data(char *syslog_data[4]) { syslog_data[0] = log_buf; syslog_data[1] = log_buf + log_buf_len;