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Message-Id: <1406031230-18107-7-git-send-email-elder@linaro.org> Date: Tue, 22 Jul 2014 07:13:49 -0500 From: Alex Elder <elder@...aro.org> To: akpm@...ux-foundation.org Cc: kay@...y.org, pmladek@...e.cz, bp@...e.de, john.stultz@...aro.org, jack@...e.cz, linux-kernel@...r.kernel.org Subject: [PATCH v6 6/7] printk: honor LOG_PREFIX in msg_print_text() This patch fixes a problem similar to what was addressed in the previous patch. All paths that read and format log records (for consoles, and for reading via syslog and /dev/kmsg) go through msg_print_text(). That function starts with some logic to determine whether the given log record when formatted should begin with a "prefix" string, and whether it should end with a newline. That logic has a bug. The LOG_PREFIX flag in a log record indicates that when it's formatted, a log record should include a prefix. This is used to force a record to begin a new line--even if its preceding log record contained LOG_CONT (indicating its content should be combined with the next record). Like the previous patch, the problem occurs when these flags are all set: prev & LOG_CONT msg->flags & LOG_PREFIX msg->flags & LOG_CONT In that case, "prefix" should be true but it is not. The fix involves checking LOG_PREFIX when a message has its LOG_CONT flag set, and in that case allowing "prefix" to become false only if LOG_PREFIX is not set. I.e., the logic for "prefix" would become: if (prev & LOG_CONT && !(msg->flags & LOG_PREFIX)) prefix = false; if (msg->flags & LOG_CONT) if (prev & LOG_CONT && !(msg->flags & LOG_PREFIX)) prefix = false; However, note that this makes the (msg->flags & LOG_CONT) block redunant--it's handled by the test just above it. The result becomes quite a bit simpler than before. The following table concisely defines the problem: prev | msg | msg || CONT |PREFIX| CONT ||prefix ------+------+------++------ clear| clear| clear|| true clear| clear| set || true clear| set | clear|| true clear| set | set || true set | clear| clear|| false set | clear| set || false set | set | clear|| true set | set | set || false <-- should be true Signed-off-by: Alex Elder <elder@...aro.org> Reviewed-by: Petr Mládek <pmladek@...e.cz> --- kernel/printk/printk.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 25b7527..b630c85 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1010,11 +1010,8 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev, if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)) prefix = false; - if (msg->flags & LOG_CONT) { - if (prev & LOG_CONT) - prefix = false; + if (msg->flags & LOG_CONT) newline = false; - } if ((prev & LOG_CONT) && (msg->flags & LOG_PREFIX) && len < size) { if (buf) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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