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authorLinus Torvalds <torvalds@linux-foundation.org>2018-10-26 03:11:52 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-10-26 03:11:52 +0300
commita67eefad996f007afc7c38efe8f45257fb1e3994 (patch)
treead8e92971827bfbb26d34fd49e7633d72f1369e2 /kernel
parent62606c224d72a98c35d21a849f95cccf95b0a252 (diff)
parent54edeb0327d7320e2a9a3e517e8bc8f318d41a77 (diff)
downloadlinux-a67eefad996f007afc7c38efe8f45257fb1e3994.tar.xz
Merge tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk updates from Petr Mladek: - Fix two more locations where printf formatting leaked pointers - Better log_buf_len parameter handling - Add prefix to messages from printk code - Do not miss messages on other consoles when the log is replayed on a new one - Reduce race between console registration and panic() when the log might get replayed on all consoles - Some cont buffer code clean up - Call console only when there is something to do (log vs cont buffer) * tag 'printk-for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: lib/vsprintf: Hash printed address for netdev bits fallback lib/vsprintf: Hash legacy clock addresses lib/vsprintf: Prepare for more general use of ptr_to_id() lib/vsprintf: Make ptr argument conts in ptr_to_id() printk: fix integer overflow in setup_log_buf() printk: do not preliminary split up cont buffer printk: lock/unlock console only for new logbuf entries printk: keep kernel cont support always enabled printk: Give error on attempt to set log buffer length to over 2G printk: Add KBUILD_MODNAME and remove a redundant print prefix printk: Correct wrong casting printk: Fix panic caused by passing log_buf_len to command line printk: CON_PRINTBUFFER console registration is a bit racy printk: Do not miss new messages when replaying the log
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk/printk.c86
1 files changed, 48 insertions, 38 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 9bf5404397e0..b77150ad1965 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -16,6 +16,8 @@
* 01Mar01 Andrew Morton
*/
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
@@ -192,16 +194,7 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
return 0;
}
-/*
- * Number of registered extended console drivers.
- *
- * If extended consoles are present, in-kernel cont reassembly is disabled
- * and each fragment is stored as a separate log entry with proper
- * continuation flag so that every emitted message has full metadata. This
- * doesn't change the result for regular consoles or /proc/kmsg. For
- * /dev/kmsg, as long as the reader concatenates messages according to
- * consecutive continuation flags, the end result should be the same too.
- */
+/* Number of registered extended console drivers. */
static int nr_ext_console_drivers;
/*
@@ -423,6 +416,7 @@ static u32 log_next_idx;
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
+static u64 exclusive_console_stop_seq;
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
@@ -437,6 +431,7 @@ static u32 clear_idx;
/* record buffer */
#define LOG_ALIGN __alignof__(struct printk_log)
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
+#define LOG_BUF_LEN_MAX (u32)(1 << 31)
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;
@@ -1037,18 +1032,28 @@ void log_buf_vmcoreinfo_setup(void)
static unsigned long __initdata new_log_buf_len;
/* we practice scaling the ring buffer by powers of 2 */
-static void __init log_buf_len_update(unsigned size)
+static void __init log_buf_len_update(u64 size)
{
+ if (size > (u64)LOG_BUF_LEN_MAX) {
+ size = (u64)LOG_BUF_LEN_MAX;
+ pr_err("log_buf over 2G is not supported.\n");
+ }
+
if (size)
size = roundup_pow_of_two(size);
if (size > log_buf_len)
- new_log_buf_len = size;
+ new_log_buf_len = (unsigned long)size;
}
/* 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);
+ u64 size;
+
+ if (!str)
+ return -EINVAL;
+
+ size = memparse(str, &str);
log_buf_len_update(size);
@@ -1093,7 +1098,7 @@ void __init setup_log_buf(int early)
{
unsigned long flags;
char *new_log_buf;
- int free;
+ unsigned int free;
if (log_buf != __log_buf)
return;
@@ -1113,7 +1118,7 @@ void __init setup_log_buf(int early)
}
if (unlikely(!new_log_buf)) {
- pr_err("log_buf_len: %ld bytes not available\n",
+ pr_err("log_buf_len: %lu bytes not available\n",
new_log_buf_len);
return;
}
@@ -1126,8 +1131,8 @@ void __init setup_log_buf(int early)
memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
logbuf_unlock_irqrestore(flags);
- pr_info("log_buf_len: %d bytes\n", log_buf_len);
- pr_info("early log buf free: %d(%d%%)\n",
+ pr_info("log_buf_len: %u bytes\n", log_buf_len);
+ pr_info("early log buf free: %u(%u%%)\n",
free, (free * 100) / __LOG_BUF_LEN);
}
@@ -1767,12 +1772,8 @@ static void cont_flush(void)
static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
{
- /*
- * If ext consoles are present, flush and skip in-kernel
- * continuation. See nr_ext_console_drivers definition. Also, if
- * the line gets too long, split it up in separate records.
- */
- if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
+ /* If the line gets too long, split it up in separate records. */
+ if (cont.len + len > sizeof(cont.buf)) {
cont_flush();
return false;
}
@@ -1795,9 +1796,6 @@ static bool cont_add(int facility, int level, enum log_flags flags, const char *
cont_flush();
}
- if (cont.len > (sizeof(cont.buf) * 80) / 100)
- cont_flush();
-
return true;
}
@@ -1889,8 +1887,9 @@ asmlinkage int vprintk_emit(int facility, int level,
const char *fmt, va_list args)
{
int printed_len;
- bool in_sched = false;
+ bool in_sched = false, pending_output;
unsigned long flags;
+ u64 curr_log_seq;
if (level == LOGLEVEL_SCHED) {
level = LOGLEVEL_DEFAULT;
@@ -1902,11 +1901,13 @@ asmlinkage int vprintk_emit(int facility, int level,
/* This stops the holder of console_sem just where we want him */
logbuf_lock_irqsave(flags);
+ curr_log_seq = log_next_seq;
printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
+ pending_output = (curr_log_seq != log_next_seq);
logbuf_unlock_irqrestore(flags);
/* If called from the scheduler, we can not call up(). */
- if (!in_sched) {
+ if (!in_sched && pending_output) {
/*
* Disable preemption to avoid being preempted while holding
* console_sem which would prevent anyone from printing to
@@ -1923,7 +1924,8 @@ asmlinkage int vprintk_emit(int facility, int level,
preempt_enable();
}
- wake_up_klogd();
+ if (pending_output)
+ wake_up_klogd();
return printed_len;
}
EXPORT_SYMBOL(vprintk_emit);
@@ -2009,6 +2011,7 @@ static u64 syslog_seq;
static u32 syslog_idx;
static u64 console_seq;
static u32 console_idx;
+static u64 exclusive_console_stop_seq;
static u64 log_first_seq;
static u32 log_first_idx;
static u64 log_next_seq;
@@ -2351,8 +2354,9 @@ again:
printk_safe_enter_irqsave(flags);
raw_spin_lock(&logbuf_lock);
if (console_seq < log_first_seq) {
- len = sprintf(text, "** %u printk messages dropped **\n",
- (unsigned)(log_first_seq - console_seq));
+ len = sprintf(text,
+ "** %llu printk messages dropped **\n",
+ log_first_seq - console_seq);
/* messages are gone, move to first one */
console_seq = log_first_seq;
@@ -2376,6 +2380,12 @@ skip:
goto skip;
}
+ /* Output to all consoles once old messages replayed. */
+ if (unlikely(exclusive_console &&
+ console_seq >= exclusive_console_stop_seq)) {
+ exclusive_console = NULL;
+ }
+
len += msg_print_text(msg,
console_msg_format & MSG_FORMAT_SYSLOG,
text + len,
@@ -2418,10 +2428,6 @@ skip:
console_locked = 0;
- /* Release the exclusive_console once it is used */
- if (unlikely(exclusive_console))
- exclusive_console = NULL;
-
raw_spin_unlock(&logbuf_lock);
up_console_sem();
@@ -2688,8 +2694,7 @@ void register_console(struct console *newcon)
}
if (newcon->flags & CON_EXTENDED)
- if (!nr_ext_console_drivers++)
- pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+ nr_ext_console_drivers++;
if (newcon->flags & CON_PRINTBUFFER) {
/*
@@ -2699,13 +2704,18 @@ void register_console(struct console *newcon)
logbuf_lock_irqsave(flags);
console_seq = syslog_seq;
console_idx = syslog_idx;
- logbuf_unlock_irqrestore(flags);
/*
* We're about to replay the log buffer. Only do this to the
* just-registered console to avoid excessive message spam to
* the already-registered consoles.
+ *
+ * Set exclusive_console with disabled interrupts to reduce
+ * race window with eventual console_flush_on_panic() that
+ * ignores console_lock.
*/
exclusive_console = newcon;
+ exclusive_console_stop_seq = console_seq;
+ logbuf_unlock_irqrestore(flags);
}
console_unlock();
console_sysfs_notify();