linux-kernel - [PATCH] drivers-core: beware dev_printk() from printing nonsense

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Message-ID: <20120820103337.GA16744@linutronix.de>
Date:	Mon, 20 Aug 2012 12:33:37 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, Jim Cromie <jim.cromie@...il.com>,
	Jason Baron <jbaron@...hat.com>,
	Kay Sievers <kay.sievers@...y.org>,
	Joe Perches <joe@...ches.com>
Subject: [PATCH] drivers-core: beware dev_printk() from printing nonsense

on boot I saw plenty of rubbish like:

|ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
|pci_root PNP0A03:00: Force enabled HPET at 0x%lx
|host bridge window [io  0x0000-0x0cf7] (ignored)
|pci_root PNP0A03:00: Force enabled HPET at 0x%lx
|host bridge window [io  0x0d00-0xffff] (ignored)
|pci_root PNP0A03:00: Force enabled HPET at 0x%lx
|ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
|virtio-pci 0000:00:05.0: Force enabled HPET at 0x%lx

First I wonder myself why the kernel Force enables more than one HPET
and why the address isn't printed. Then I wasn't sure why virtio-pci
does the same thing.
As it turns out commit af7f2158fdee ("drivers-core: make structured
logging play nice with dynamic-debug") has probably an off by one error.
Since commit 314ba3520 ("printk: add kern_levels.h to make KERN_<LEVEL>
available for asm use") the whole shrunk by one byte. And for some
reason the compiler put the HPET string just after one of the kernel log
levels so level[3] was always true.

This should make the rubish go away, I am not sure if the dynamic debug
is still working. Jim could you please try?

Cc: Jim Cromie <jim.cromie@...il.com>
Cc: Jason Baron <jbaron@...hat.com>
Cc: stable <stable@...r.kernel.org>
Cc: Kay Sievers <kay.sievers@...y.org>
Cc: Joe Perches <joe@...ches.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 drivers/base/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index cdd01c5..5a864c3 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1912,7 +1912,7 @@ int __dev_printk(const char *level, const struct device *dev,
 				    "DEVICE=+%s:%s", subsys, dev_name(dev));
 	}
 skip:
-	if (level[3])
+	if (level[sizeof(KERN_ERR) - 1])
 		level_extra = &level[3]; /* skip past "<L>" */
 
 	return printk_emit(0, level[1] - '0',
-- 
1.7.10.4

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