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authorKay Sievers <kay@vrfy.org>2012-07-09 10:05:10 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-07-09 10:05:10 -0700
commiteb02dac93708f581c99858a19162af8ca2b6bfcb (patch)
tree2e749f4599eff44107ecedea84eacd51a859a6a5 /kernel/printk.c
parent68b6507dc554ba015b5ed5e13b1ed4993cdf4024 (diff)
downloadlinux-eb02dac93708f581c99858a19162af8ca2b6bfcb.tar.gz
kmsg: /proc/kmsg - support reading of partial log records
Restore support for partial reads of any size on /proc/kmsg, in case the supplied read buffer is smaller than the record size. Some people seem to think is is ia good idea to run: $ dd if=/proc/kmsg bs=1 of=... as a klog bridge. Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44211 Reported-by: Jukka Ollila <jiiksteri@gmail.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/printk.c')
-rw-r--r--kernel/printk.c28
1 files changed, 20 insertions, 8 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index f02f1f5ddc3..50c33411442 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -217,6 +217,7 @@ static DEFINE_RAW_SPINLOCK(logbuf_lock);
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
+static size_t syslog_partial;
/* index and sequence number of the first record stored in the buffer */
static u64 log_first_seq;
@@ -890,22 +891,33 @@ static int syslog_print(char __user *buf, int size)
while (size > 0) {
size_t n;
+ size_t skip;
raw_spin_lock_irq(&logbuf_lock);
if (syslog_seq < log_first_seq) {
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
+ syslog_partial = 0;
}
if (syslog_seq == log_next_seq) {
raw_spin_unlock_irq(&logbuf_lock);
break;
}
+
+ skip = syslog_partial;
msg = log_from_idx(syslog_idx);
n = msg_print_text(msg, true, text, LOG_LINE_MAX);
- if (n <= size) {
+ if (n - syslog_partial <= size) {
+ /* message fits into buffer, move forward */
syslog_idx = log_next(syslog_idx);
syslog_seq++;
+ n -= syslog_partial;
+ syslog_partial = 0;
+ } else if (!len){
+ /* partial read(), remember position */
+ n = size;
+ syslog_partial += n;
} else
n = 0;
raw_spin_unlock_irq(&logbuf_lock);
@@ -913,17 +925,15 @@ static int syslog_print(char __user *buf, int size)
if (!n)
break;
- len += n;
- size -= n;
- buf += n;
- n = copy_to_user(buf - n, text, n);
-
- if (n) {
- len -= n;
+ if (copy_to_user(buf, text + skip, n)) {
if (!len)
len = -EFAULT;
break;
}
+
+ len += n;
+ size -= n;
+ buf += n;
}
kfree(text);
@@ -1107,6 +1117,7 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
/* messages are gone, move to first one */
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
+ syslog_partial = 0;
}
if (from_file) {
/*
@@ -1129,6 +1140,7 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
idx = log_next(idx);
seq++;
}
+ error -= syslog_partial;
}
raw_spin_unlock_irq(&logbuf_lock);
break;