fix on rt-tests of backfire kernel module

fix on rt-tests of backfire kernel module

[Michele Dionisio]

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Hi all,
I'm new in this mailing list. I start to work/test PREEPT_RT and
making some test I seee that there is a bug on backfire module in
rt-tests repository.

I'm attaching my patch.

best regards.
Michele

[-- Attachment #2: backfire_copyto_from_userspace.patch --]
[-- Type: text/x-patch, Size: 2513 bytes --]

From cd94ede8cf9eb8c26a196ea0111220969451cbb2 Mon Sep 17 00:00:00 2001
From: Michele Dionisio <michele.dionisio@powersoft.it>
Date: Tue, 26 Sep 2017 14:32:51 +0200
Subject: [FIX] fix copy data to and from userspace


diff --git a/src/backfire/backfire.c b/src/backfire/backfire.c
index aaf9c4a..b38651b 100644
--- a/src/backfire/backfire.c
+++ b/src/backfire/backfire.c
@@ -20,11 +20,9 @@
  */
 
 #include <linux/module.h>
-
 #include <linux/sched.h>
 #include <linux/cpumask.h>
 #include <linux/time.h>
-#include <linux/smp_lock.h>
 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/miscdevice.h>
@@ -32,25 +30,33 @@
 #include <linux/spinlock.h>
 
 #include <asm/uaccess.h>
-#include <asm/system.h>
 
 #define BACKFIRE_MINOR MISC_DYNAMIC_MINOR
 
-static spinlock_t backfire_state_lock = SPIN_LOCK_UNLOCKED;
+static DEFINE_SPINLOCK(backfire_state_lock);
 static int backfire_open_cnt; /* #times opened */
 static int backfire_open_mode; /* special open modes */
 static struct timeval sendtime; /* when the most recent signal was sent */
 #define BACKFIRE_WRITE 1 /* opened for writing (exclusive) */
 #define BACKFIRE_EXCL 2 /* opened with O_EXCL */
 
+#define MAX_SIZE_DATA_RW 512
+
 /*
  * These are the file operation function for user access to /dev/backfire
  */
 static ssize_t
 backfire_read(struct file *file, char *buf, size_t count, loff_t *ppos)
 {
-	return snprintf(buf, count, "%d,%d\n", (int) sendtime.tv_sec,
+    char kbuf[MAX_SIZE_DATA_RW];
+    ssize_t res;
+    if (count > MAX_SIZE_DATA_RW) {
+        count = MAX_SIZE_DATA_RW;
+    }
+	res = snprintf(kbuf, count, "%d,%d\n", (int) sendtime.tv_sec,
 		(int) sendtime.tv_usec);
+    copy_to_user(buf, kbuf, res+1);
+    return res;
 }
 
 static ssize_t
@@ -58,16 +64,28 @@ backfire_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
 {
 	int signo;
 	struct pid *pid;
-
-	if (sscanf(buf, "%d", &signo) >= 1) {
+    char kbuf[MAX_SIZE_DATA_RW+1];
+    ssize_t retval = 0;
+    
+    if (count == 0) {
+        return 0;
+    }
+    if (count > MAX_SIZE_DATA_RW) {
+        count = MAX_SIZE_DATA_RW;
+    }
+    copy_from_user(kbuf, buf, count);
+    kbuf[count] = '\0';
+
+	if (sscanf(kbuf, "%d", &signo) >= 1) {
 		if (signo > 0 && signo < 32) {
 			pid = get_pid(task_pid(current));
 			do_gettimeofday(&sendtime);
 			kill_pid(pid, signo, 1);
+            retval = strlen(kbuf);
 		} else
 			printk(KERN_ERR "Invalid signal no. %d\n", signo);
 	}
-	return strlen(buf);
+	return retval;
 }
 
 static int

Re: fix on rt-tests of backfire kernel module

[Julia Cartwright]

On Wed, Sep 27, 2017 at 09:15:11AM +0200, Michele Dionisio wrote:
> Hi all,
>
> I'm new in this mailing list.

Welcome!

> I start to work/test PREEPT_RT and making some test I seee that there
> is a bug on backfire module in rt-tests repository.

At the very least, you'll want to elaborate on the bug you were seeing.
What broke?  What did you expect to see?  What did you see instead?  Is
this a build time problem?  A run-time problem?  How does your fix
prevent this problem from occurring?

Also, for rt-tests patches, you'll want to ensure to CC John Kacur and
Clark Williams, who are maintaining the project.

> I'm attaching my patch.
>
> best regards.
> Michele


> From cd94ede8cf9eb8c26a196ea0111220969451cbb2 Mon Sep 17 00:00:00 2001
> From: Michele Dionisio <michele.dionisio@powersoft.it>
> Date: Tue, 26 Sep 2017 14:32:51 +0200
> Subject: [FIX] fix copy data to and from userspace

You'll want to include a changelog here, describing the above.  This is
what will go into the git permanent history.

> diff --git a/src/backfire/backfire.c b/src/backfire/backfire.c
> index aaf9c4a..b38651b 100644
> --- a/src/backfire/backfire.c
> +++ b/src/backfire/backfire.c
> @@ -20,11 +20,9 @@
[..]
> +#define MAX_SIZE_DATA_RW 512
> +
>  /*
>   * These are the file operation function for user access to /dev/backfire
>   */
>  static ssize_t
>  backfire_read(struct file *file, char *buf, size_t count, loff_t *ppos)
>  {
> -	return snprintf(buf, count, "%d,%d\n", (int) sendtime.tv_sec,
> +    char kbuf[MAX_SIZE_DATA_RW];
> +    ssize_t res;
> +    if (count > MAX_SIZE_DATA_RW) {
> +        count = MAX_SIZE_DATA_RW;
> +    }
> +	res = snprintf(kbuf, count, "%d,%d\n", (int) sendtime.tv_sec,
>  		(int) sendtime.tv_usec);
> +    copy_to_user(buf, kbuf, res+1);
> +    return res;

Your patch is also whitespace damaged.  You'll want to ensure to follow
the kernel's CodingStyle here (which is 8-space tabstops).

   Julia

Re: fix on rt-tests of backfire kernel module

[Uwe Kleine-König]

Hello Michele,

On Wed, Sep 27, 2017 at 09:15:11AM +0200, Michele Dionisio wrote:
> Hi all,
> I'm new in this mailing list. I start to work/test PREEPT_RT and
> making some test I seee that there is a bug on backfire module in
> rt-tests repository.
> 
> I'm attaching my patch.

I didn't look in detail into your patch, but I guess most of your stuff
was already addressed before in a thread here. See

	https://marc.info/?t=131384496800001&r=1&w=2

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: fix on rt-tests of backfire kernel module

[michele.dionisio]

Ok. It is true. The only missing part is copy from/to userspace.

If you suggest me a git repo from where i can start to work I will prepare a better patch with only that fix.

Regards

Il Venerdì 29 settembre 2017, Uwe Kleine-König scrive:
> Hello Michele,
> 
> On Wed, Sep 27, 2017 at 09:15:11AM +0200, Michele Dionisio wrote:
> > Hi all,
> > I'm new in this mailing list. I start to work/test PREEPT_RT and
> > making some test I seee that there is a bug on backfire module in
> > rt-tests repository.
> > 
> > I'm attaching my patch.
> 
> I didn't look in detail into your patch, but I guess most of your stuff
> was already addressed before in a thread here. See
> 
> 	https://marc.info/?t=131384496800001&r=1&w=2
> 
> Best regards
> Uwe
> 
> -- 
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
>