linux-kernel - [PATCH] mtd: phram: error handling

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Date:	Wed, 11 Nov 2015 13:53:58 +0530
From:	Saurabh Sengar <saurabh.truth@...il.com>
To:	computersforpeace@...il.com, joe@...ches.com
Cc:	andy.shevchenko@...il.com, joern@...ybastard.org,
	dwmw2@...radead.org, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mtd: phram: error handling


Brian Norris wrote:
> Well, today you're in luck! You're touching a driver that requires no
> special hardware, so you should be able to test it.

> I think you can try using the mem= kernel parameter (see
> Documentation/kernel-parameters.txt) to restrict your system memory, and
> then try using that unreachable portions of memory for phram. You can
> try this driver as either a module or built-in. For the former, you can
> specify the parameters during modprobe time, or later by writing to
> /sys/module/phram/parameters/phram. For the latter, you can specify on
> the kernel command line or in /sys/module/phram/parameters/phram.

> Let me know if you have any more questions about testing your patch.


Hi Brian,

As you have suggested I have restricted my laptop's memory to 1GB and tried to access unreachable portion of memory(2GB).
It seems to be successfully registered(this is OK right ?).

I have also tested below error scenarios; all exiting gracefully
  - parameter too long
  - too many arguments
  - not enough arguments
  - invalid start adddress
  - invalid device length


This is my first interaction with phram device so I request you to verify my testing.
Below are the commands and output I did for this testing.

-----------------------------------------------------
  <restricting memory of my machine to 1 GB>
saurabh@...rabh:~/little/Task02/linux$ cat /proc/meminfo | grep Mem
MemTotal:        1016588 kB
MemFree:          126016 kB
MemAvailable:     295508 kB
saurabh@...rabh:~/little/Task02/linux$ cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-4.3.0-10333-gdfe4330-dirty mem=1024M root=UUID=2b66d4b2-ac21-4554-bf3b-64bc973e1dad ro quiet splash vt.handoff=7

  <accessing unreachable portions of memory>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=ram,2048Mi,1ki
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[  634.748495] phram: ram device: 0x400 at 0x80000000

  <parameter too long>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz,256Mi,1Mi
insmod: ERROR: could not insert module drivers/mtd/devices/phram.ko: Invalid parameters
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[ 1469.763787] phram: parameter too long
[ 1469.763797] phram: `abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz,256Mi,1Mi' invalid for parameter `phram'


  <too many arguments>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=swap,256Mi,1Mi,extra_parameter
insmod: ERROR: could not insert module drivers/mtd/devices/phram.ko: Invalid parameters
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[ 1650.081694] phram: too many arguments
[ 1650.081703] phram: `swap,256Mi,1Mi,extra_parameter' invalid for parameter `phram'

  <not enough arguments>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=swap,256Mi
insmod: ERROR: could not insert module drivers/mtd/devices/phram.ko: Invalid parameters
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[ 1707.437130] phram: not enough arguments
[ 1707.437138] phram: `swap,256Mi' invalid for parameter `phram'


  <invalid start address>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=swap,256xyz,1Mi
insmod: ERROR: could not insert module drivers/mtd/devices/phram.ko: Invalid parameters
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[ 1783.014351] phram: invalid start address
[ 1783.014359] phram: `swap,256xyz,1Mi' invalid for parameter `phram'

  <invalid device length>
saurabh@...rabh:~/little/Task02/linux$ sudo insmod drivers/mtd/devices/phram.ko phram=swap,256Mi,1xyz
insmod: ERROR: could not insert module drivers/mtd/devices/phram.ko: Invalid parameters
saurabh@...rabh:~/little/Task02/linux$ sudo dmesg -c
[ 1831.746108] phram: invalid device length
[ 1831.746117] phram: `swap,256Mi,1xyz' invalid for parameter `phram'
-------------------------------------------
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