[PATCH] staging: dgnc: fix compile warning frame size is larger than 1024 bytes

[PATCH] staging: dgnc: fix compile warning frame size is larger than 1024 bytes

[Martin Kepplinger]

fix following warning by dynamically allocating memory:
dgnc_tty.c:583:1: warning: the frame size of 1060 bytes is larger than 1024 bytes [-Wframe-larger-than=]

Signed-off-by: Martin Kepplinger <martink@posteo.de>
---
This is more of a question. Is this a desired solution to fixing such a
frame size warning?

thanks,
                martin

 drivers/staging/dgnc/dgnc_tty.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_tty.c b/drivers/staging/dgnc/dgnc_tty.c
index f0b17c3..1c78cc2 100644
--- a/drivers/staging/dgnc/dgnc_tty.c
+++ b/drivers/staging/dgnc/dgnc_tty.c
@@ -481,8 +481,8 @@ void dgnc_sniff_nowait_nolock(struct channel_t *ch, uchar *text, uchar *buf, int
 	int nbuf;
 	int i;
 	int tmpbuflen;
-	char tmpbuf[TMPBUFLEN];
-	char *p = tmpbuf;
+	char *tmpbuf;
+	char *p;
 	int too_much_data;
 
 	/* Leave if sniff not open */
@@ -492,6 +492,13 @@ void dgnc_sniff_nowait_nolock(struct channel_t *ch, uchar *text, uchar *buf, int
 	do_gettimeofday(&tv);
 
 	/* Create our header for data dump */
+	tmpbuf = kmalloc(TMPBUFLEN, GFP_KERNEL);
+	if (!tmpbuf) {
+		pr_err("dgnc: memory allocation error\n");
+		return;
+	}
+	p = tmpbuf;
+
 	p += sprintf(p, "<%ld %ld><%s><", tv.tv_sec, tv.tv_usec, text);
 	tmpbuflen = p - tmpbuf;
 
-- 
1.7.10.4

Re: [PATCH] staging: dgnc: fix compile warning frame size is larger than 1024 bytes

[Dan Carpenter]

On Tue, May 06, 2014 at 02:41:37PM +0200, Martin Kepplinger wrote:
> fix following warning by dynamically allocating memory:
> dgnc_tty.c:583:1: warning: the frame size of 1060 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> Signed-off-by: Martin Kepplinger <martink@posteo.de>
> ---
> This is more of a question. Is this a desired solution to fixing such a
> frame size warning?

This warning is because the kernel uses an 8k stack so you add up all
the stack memory used by each function from the syscall to here.  If
it adds up to more than 8k then it's a bug.  The 1k limit per function
is just a hack to spot where people are maybe being reckless.

There are no kfree()s and this function is called with a spin_lock held
so this patch introduces a couple bugs.

There may be a better way to allocate this.  Like maybe at probe() and
then use spinlocks to serialize access to the buffer.  But sometimes
that's a very bad idea.

It's better if you know the driver a bit and can test things.

regards,
dan carpenter

Re: [PATCH] staging: dgnc: fix compile warning frame size is larger than 1024 bytes

[Martin Kepplinger]

Am 2014-05-06 15:33, schrieb Dan Carpenter:
> On Tue, May 06, 2014 at 02:41:37PM +0200, Martin Kepplinger wrote:
>> fix following warning by dynamically allocating memory:
>> dgnc_tty.c:583:1: warning: the frame size of 1060 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>>
>> Signed-off-by: Martin Kepplinger <martink@posteo.de>
>> ---
>> This is more of a question. Is this a desired solution to fixing such a
>> frame size warning?
> 
> This warning is because the kernel uses an 8k stack so you add up all
> the stack memory used by each function from the syscall to here.  If
> it adds up to more than 8k then it's a bug.  The 1k limit per function
> is just a hack to spot where people are maybe being reckless.

nice. thanks.

> 
> There are no kfree()s and this function is called with a spin_lock held
> so this patch introduces a couple bugs.

I know, it should have been just a question (probably to kernelnewbies'
list). Sorry for the noise.

> 
> There may be a better way to allocate this.  Like maybe at probe() and
> then use spinlocks to serialize access to the buffer.  But sometimes
> that's a very bad idea.
> 
> It's better if you know the driver a bit and can test things.
> 
> regards,
> dan carpenter
> 
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