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Message-ID: <20120718175625.GD21746@redhat.com>
Date: Wed, 18 Jul 2012 13:56:26 -0400
From: Vivek Goyal <vgoyal@...hat.com>
To: Kay Sievers <kay@...y.org>
Cc: linux kernel mailing list <linux-kernel@...r.kernel.org>,
Kexec Mailing List <kexec@...ts.infradead.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartmann <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] printk: Export struct log size and member offsets
through vmcoreinfo
On Wed, Jul 18, 2012 at 07:27:08PM +0200, Kay Sievers wrote:
> On Wed, Jul 18, 2012 at 7:18 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
>
> > Currently I am not exporting log "level" info as that is a bitfield and
> > offsetof() bitfields can't be calculated.
>
> We could make the level the lower 3 bits of the byte, export the byte,
> and define that only 3 bits of the byte are valid? Would that help?
Yes, that should work. Here is the prototype patch which stores 5 bits
of flag and 3 bits of level in a byte. I have not tested it yet, but
if you like the approach, I will test it.
Thanks
Vivek
---
kernel/printk.c | 48 +++++++++++++++++++++++++++++-------------------
1 file changed, 29 insertions(+), 19 deletions(-)
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c 2012-07-20 14:02:42.000000000 -0400
+++ linux-2.6/kernel/printk.c 2012-07-20 16:34:24.088964153 -0400
@@ -200,14 +200,19 @@ enum log_flags {
LOG_CONT = 8, /* text is a fragment of a continuation line */
};
+#define LOG_FLAG_SHIFT 3
+#define LOG_LEVEL_MASK ((1 << LOG_FLAG_SHIFT) - 1)
+#define LOG_FLAGS(log) ((log)->flags_level >> LOG_FLAG_SHIFT)
+#define LOG_LEVEL(log) (((log)->flags_level) & LOG_LEVEL_MASK)
+
struct log {
u64 ts_nsec; /* timestamp in nanoseconds */
u16 len; /* length of entire record */
u16 text_len; /* length of text buffer */
u16 dict_len; /* length of dictionary buffer */
u8 facility; /* syslog facility */
- u8 flags:5; /* internal record flags */
- u8 level:3; /* syslog level */
+ u8 flags_level; /* 5 bit internal record flags, 3 bits syslog
+ * level */
};
/*
@@ -342,8 +347,8 @@ static void log_store(int facility, int
memcpy(log_dict(msg), dict, dict_len);
msg->dict_len = dict_len;
msg->facility = facility;
- msg->level = level & 7;
- msg->flags = flags & 0x1f;
+ msg->flags_level = level & 7;
+ msg->flags_level |= (flags & 0x1f) << LOG_FLAG_SHIFT;
if (ts_nsec > 0)
msg->ts_nsec = ts_nsec;
else
@@ -463,7 +468,8 @@ static ssize_t devkmsg_read(struct file
ts_usec = msg->ts_nsec;
do_div(ts_usec, 1000);
len = sprintf(user->buf, "%u,%llu,%llu;",
- (msg->facility << 3) | msg->level, user->seq, ts_usec);
+ (msg->facility << 3) | LOG_LEVEL(msg), user->seq,
+ ts_usec);
/* escape non-printable characters */
for (i = 0; i < msg->text_len; i++) {
@@ -655,6 +661,8 @@ void log_buf_kexec_setup(void)
VMCOREINFO_OFFSET(log, len);
VMCOREINFO_OFFSET(log, text_len);
VMCOREINFO_OFFSET(log, dict_len);
+ VMCOREINFO_OFFSET(log, flags_level);
+ VMCOREINFO_LENGTH(log_level_bits, 3);
}
#endif
@@ -831,7 +839,7 @@ static size_t print_time(u64 ts, char *b
static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
{
size_t len = 0;
- unsigned int prefix = (msg->facility << 3) | msg->level;
+ unsigned int prefix = (msg->facility << 3) | LOG_LEVEL(msg);
if (syslog) {
if (buf) {
@@ -860,14 +868,14 @@ static size_t msg_print_text(const struc
bool newline = true;
size_t len = 0;
- if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
+ if ((prev & LOG_CONT) && !(LOG_FLAGS(msg) & LOG_PREFIX))
prefix = false;
- if (msg->flags & LOG_CONT) {
+ if (LOG_FLAGS(msg) & LOG_CONT) {
if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
prefix = false;
- if (!(msg->flags & LOG_NEWLINE))
+ if (!(LOG_FLAGS(msg) & LOG_NEWLINE))
newline = false;
}
@@ -944,7 +952,7 @@ static int syslog_print(char __user *buf
/* message fits into buffer, move forward */
syslog_idx = log_next(syslog_idx);
syslog_seq++;
- syslog_prev = msg->flags;
+ syslog_prev = LOG_FLAGS(msg);
n -= syslog_partial;
syslog_partial = 0;
} else if (!len){
@@ -1038,7 +1046,7 @@ static int syslog_print_all(char __user
}
idx = log_next(idx);
seq++;
- prev = msg->flags;
+ prev = LOG_FLAGS(msg);
raw_spin_unlock_irq(&logbuf_lock);
if (copy_to_user(buf + len, text, textlen))
@@ -1178,7 +1186,7 @@ int do_syslog(int type, char __user *buf
error += msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
- prev = msg->flags;
+ prev = LOG_FLAGS(msg);
}
error -= syslog_partial;
}
@@ -1979,6 +1987,7 @@ again:
struct log *msg;
size_t len;
int level;
+ u16 log_flags;
raw_spin_lock_irqsave(&logbuf_lock, flags);
if (seen_seq != log_next_seq) {
@@ -1997,7 +2006,7 @@ skip:
break;
msg = log_from_idx(console_idx);
- if (msg->flags & LOG_NOCONS) {
+ if (LOG_FLAGS(msg) & LOG_NOCONS) {
/*
* Skip record we have buffered and already printed
* directly to the console when we received it.
@@ -2009,16 +2018,17 @@ skip:
* CON_PRINTBUFFER console. Clear the flag so we
* will properly dump everything later.
*/
- msg->flags &= ~LOG_NOCONS;
+ log_flags = LOG_FLAGS(msg) & ~ LOG_NOCONS;
+ msg->flags_level = log_flags << LOG_FLAG_SHIFT | LOG_LEVEL(msg);
goto skip;
}
- level = msg->level;
+ level = LOG_LEVEL(msg);
len = msg_print_text(msg, console_prev, false,
text, sizeof(text));
console_idx = log_next(console_idx);
console_seq++;
- console_prev = msg->flags;
+ console_prev = LOG_FLAGS(msg);
raw_spin_unlock(&logbuf_lock);
stop_critical_timings(); /* don't trace print latency */
@@ -2645,7 +2655,7 @@ bool kmsg_dump_get_buffer(struct kmsg_du
l += msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
- prev = msg->flags;
+ prev = LOG_FLAGS(msg);
}
/* move first record forward until length fits into the buffer */
@@ -2658,7 +2668,7 @@ bool kmsg_dump_get_buffer(struct kmsg_du
l -= msg_print_text(msg, prev, true, NULL, 0);
idx = log_next(idx);
seq++;
- prev = msg->flags;
+ prev = LOG_FLAGS(msg);
}
/* last message in next interation */
@@ -2673,7 +2683,7 @@ bool kmsg_dump_get_buffer(struct kmsg_du
l += msg_print_text(msg, prev, syslog, buf + l, size - l);
idx = log_next(idx);
seq++;
- prev = msg->flags;
+ prev = LOG_FLAGS(msg);
}
dumper->next_seq = next_seq;
--
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