Add some clarity to the printk subsystem by restructuring
the code a bit.
Move the log_buf variables and functions to separate
code and header files.
Signed-off-by: Joe Perches <joe@xxxxxxxxxxx>
---
kernel/printk/Makefile | 3 +-
kernel/printk/log_buf.c | 268 ++++++++++++++++++++++++++++++++++++++++++++
kernel/printk/log_buf.h | 27 +++++
kernel/printk/printk.c | 283 ++++-------------------------------------------
4 files changed, 317 insertions(+), 264 deletions(-)
create mode 100644 kernel/printk/log_buf.c
create mode 100644 kernel/printk/log_buf.h
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index 6bae497..2fc9fe7 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -1 +1,2 @@
-obj-y += printk.o
+obj-y += printk.o
+obj-y += log_buf.o
diff --git a/kernel/printk/log_buf.c b/kernel/printk/log_buf.c
new file mode 100644
index 0000000..b75acf3
--- /dev/null
+++ b/kernel/printk/log_buf.c
@@ -0,0 +1,268 @@
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/jiffies.h>
+#include <linux/bootmem.h>
+#include <linux/memblock.h>
+#include <linux/kexec.h>
+#include <linux/syslog.h>
+#include <linux/uaccess.h>
+
+#include "log_buf.h"
+
+extern struct semaphore console_sem;
+
+/*
+ * 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();.
+ */
+DEFINE_RAW_SPINLOCK(logbuf_lock);
+
+DECLARE_WAIT_QUEUE_HEAD(log_wait);
+
+/*
+ * These indices into log_buf are not constrained to log_buf_len
+ * they must be masked before subscripting
+ */
+unsigned log_start; /* next char to be read by syslog() */
+unsigned con_start; /* next char to be sent to consoles */
+unsigned log_end; /* most-recently-written-char + 1 */
+
+char __log_buf[__LOG_BUF_LEN];
+char *log_buf = __log_buf;
+int log_buf_len = __LOG_BUF_LEN;
+
+unsigned logged_chars; /* Number of chars produced since last
+ * read+clear operation
+ */
+
+#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;
+
+int log_buf_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 = 0;
+
+ switch (type) {
+ 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;
+ case SYSLOG_ACTION_READ_CLEAR: /* Read/clear last kernel messages */
+ do_clear = 1;
+ /* FALL THRU */
+ case SYSLOG_ACTION_READ_ALL: /* Read last kernel messages */
+ 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;
+ case SYSLOG_ACTION_CLEAR: /* Clear ring buffer */
+ logged_chars = 0;
+ break;
+ case SYSLOG_ACTION_SIZE_UNREAD: /* Number of chars in the log buffer */
+ error = log_end - log_start;
+ break;
+ case SYSLOG_ACTION_SIZE_BUFFER: /* Size of the log buffer */
+ error = log_buf_len;
+ break;
+ }
+out:
+ return error;
+}
+
+/* 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)
+ 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);
+}
+
+void log_buf_emit_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++;
+}
+
+/*
+ * Zap console related locks when oopsing. Only zap at most once
+ * every 10 seconds, to leave time for slow consoles to print a
+ * full oops.
+ */
+void log_buf_zap_locks(void)
+{
+ static unsigned long oops_timestamp;
+
+ if (time_after_eq(jiffies, oops_timestamp) &&
+ !time_after(jiffies, oops_timestamp + 30 * HZ))
+ return;
+
+ oops_timestamp = jiffies;
+
+ debug_locks_off();
+ /* If a crash is occurring, make sure we can't deadlock */
+ raw_spin_lock_init(&logbuf_lock);
+ /* And make sure that we print immediately */
+ sema_init(&console_sem, 1);
+}
diff --git a/kernel/printk/log_buf.h b/kernel/printk/log_buf.h
new file mode 100644
index 0000000..08ed8ee
--- /dev/null
+++ b/kernel/printk/log_buf.h
@@ -0,0 +1,27 @@
+#ifndef PRINTK_LOG_BUF_H
+#define PRINTK_LOG_BUF_H
+
+#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
+
+extern unsigned log_start; /* next char to be read by syslog() */
+extern unsigned con_start; /* next char to be sent to consoles */
+extern unsigned log_end; /* most-recently-written-char + 1 */
+extern unsigned logged_chars; /* Number of chars produced since last
+ * read+clear operation
+ */
+
+extern raw_spinlock_t logbuf_lock;
+extern wait_queue_head_t log_wait;
+
+extern char __log_buf[__LOG_BUF_LEN];
+extern char *log_buf;
+extern int log_buf_len;
+
+#define LOG_BUF_MASK (log_buf_len - 1)
+#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
+
+int log_buf_do_syslog(int type, char __user *buf, int len, bool from_file);
+void log_buf_emit_char(char c);
+void log_buf_zap_locks(void);
+
+#endif
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d98c094..e90818a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -15,11 +15,9 @@
*/
#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>
@@ -28,10 +26,7 @@
#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>
@@ -52,8 +47,6 @@ 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
@@ -61,8 +54,6 @@ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
#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 */
@@ -82,7 +73,8 @@ EXPORT_SYMBOL(oops_in_progress);
* provides serialisation for access to the entire console
* driver system.
*/
-static DEFINE_SEMAPHORE(console_sem);
+DEFINE_SEMAPHORE(console_sem);
+
struct console *console_drivers;
EXPORT_SYMBOL_GPL(console_drivers);
@@ -97,24 +89,6 @@ EXPORT_SYMBOL_GPL(console_drivers);
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;
@@ -145,98 +119,9 @@ 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)
- 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);
+#include "log_buf.h"
- 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);
-}
+static int saved_console_loglevel = -1;
#ifdef CONFIG_BOOT_PRINTK_DELAY
@@ -332,9 +217,6 @@ static int check_syslog_permissions(int type, bool from_file)
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);
@@ -350,99 +232,16 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
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;
+ case SYSLOG_ACTION_READ_CLEAR: /* Read/clear last kernel messages */
+ case SYSLOG_ACTION_READ_ALL: /* Read last kernel messages */
+ case SYSLOG_ACTION_CLEAR: /* Clear ring buffer */
+ case SYSLOG_ACTION_SIZE_UNREAD: /* Number of chars in the log buffer */
+ case SYSLOG_ACTION_SIZE_BUFFER: /* Size of the log buffer */
+ error = log_buf_do_syslog(type, buf, len, from_file);
break;
+
/* Disable logging to console */
case SYSLOG_ACTION_CONSOLE_OFF:
if (saved_console_loglevel == -1)
@@ -468,14 +267,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
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;
@@ -664,40 +455,6 @@ static void call_console_drivers(unsigned start, unsigned end)
_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++;
-}
-
-/*
- * Zap console related locks when oopsing. Only zap at most once
- * every 10 seconds, to leave time for slow consoles to print a
- * full oops.
- */
-static void zap_locks(void)
-{
- static unsigned long oops_timestamp;
-
- if (time_after_eq(jiffies, oops_timestamp) &&
- !time_after(jiffies, oops_timestamp + 30 * HZ))
- return;
-
- oops_timestamp = jiffies;
-
- debug_locks_off();
- /* If a crash is occurring, make sure we can't deadlock */
- raw_spin_lock_init(&logbuf_lock);
- /* And make sure that we print immediately */
- sema_init(&console_sem, 1);
-}
-
#if defined(CONFIG_PRINTK_TIME)
static bool printk_time = 1;
#else
@@ -866,7 +623,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
recursion_bug = 1;
goto out_restore_irqs;
}
- zap_locks();
+ log_buf_zap_locks();
}
lockdep_off();
@@ -897,7 +654,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
plen = 0;
default:
if (!new_text_line) {
- emit_log_char('\n');
+ log_buf_emit_char('\n');
new_text_line = 1;
}
}
@@ -916,13 +673,13 @@ asmlinkage int vprintk(const char *fmt, va_list args)
int i;
for (i = 0; i < plen; i++)
- emit_log_char(printk_buf[i]);
+ log_buf_emit_char(printk_buf[i]);
printed_len += plen;
} else {
/* Add log prefix */
- emit_log_char('<');
- emit_log_char(current_log_level + '0');
- emit_log_char('>');
+ log_buf_emit_char('<');
+ log_buf_emit_char(current_log_level + '0');
+ log_buf_emit_char('>');
printed_len += 3;
}
@@ -940,7 +697,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
nanosec_rem / 1000);
for (tp = tbuf; tp < tbuf + tlen; tp++)
- emit_log_char(*tp);
+ log_buf_emit_char(*tp);
printed_len += tlen;
}
@@ -948,7 +705,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
break;
}
- emit_log_char(*p);
+ log_buf_emit_char(*p);
if (*p == '\n')
new_text_line = 1;
}
--
1.7.8.111.gad25c.dirty
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