kaiwan / device-memory-readwrite Goto Github PK

Test case:
On a QEMU-emulated (Versatile Express CA-9) platform (in fact, I use my other opensource project - SEALS - to do so):

ARM # insmod ./rwmem.ko
rwmem: registered with major number 252
rwmem: cdev rwmem.0 added
 rwmem: Device node /dev/rwmem.0 created.
rwmem: IO base address NOT specified (or len invalid) as module param; not performing ioremap...
ARM # ls /dev/rwmem*
ls: /dev/rwmem*: No such file or directory
ARM # 

I had to manually create the device node:

ARM # mknod /dev/rwmem.0 c 252 0
ARM # ls -l /dev/rwmem.0 
crw-r--r--    1 0        0         252,   0 Oct  7 04:01 /dev/rwmem.0
ARM # 

Then everything works just fine. For eg.:

ARM # ./rdmem 80000000 32
PID 620. [Enter] to cont...
PRINT_CTX:: in function rwmem_ioctl on cpu # 0
 in process context: rdmem:620
        +0          +4          +8          +c            0   4   8   c   
+0000   00 00 a1 ff 00 00 00 0e 57 f6 34 7b 54 9b ed 86   ........W.4{T...
+0010   54 9b ed 6e 00 00 00 00 00 01 00 00 00 00 00 00   T..n............
+0020   00 00 00 00 00 00 00 01 62 2f 2e 2e 62 2f 6e 69   ........b/..b/ni
+0030   62 79 73 75 00 00 78 6f 00 00 00 00 00 00 00 00   bysu..xo........
ARM # 

But how come the device node is not created (works on x86)?

TODO - have it work for Port IO as well...

Request a general code review. Thanks!

Original issue reported on code.google.com by [email protected] on 25 Jul 2011 at 7:56

First: I use the tool to access the PINMUX control registers on a TI AM335x ARM Cortex-A8. These are protected, so that you need the Kernel Mode for writes.

I define an iobase with
insmod devmem_rw.ko iobase_start=0x44E10000 iobase_len=0x100

./wrmem -o 860 27 (e.g.) didn't work (... user mode)

At line 98 I added the first "if", like it is used in RDMEM:
if (st_wrm.flag != USE_IOBASE) {
if (is_user_address(st_wrm.addr)) {
if (uaddr_valid(st_wrm.addr) == -1) {
fprintf(stderr,
"%s: the (usermode virtual) address passed (%p) seems to be invalid. Aborting...\n",
argv[0], (void *)st_wrm.addr);
close(fd);
exit(1);
}
}
}

I didn't analyse the code in depth, as this worked right away. So I don't know if this is a good solution.

Applicable to ver 0.1.2 :

What steps will reproduce the problem?
1. 'make' on the device driver

What is the expected output? What do you see instead?
$ make
...
rwmem.c:271: warning: initialization from incompatible pointer type
...
$ 

Original issue reported on code.google.com by [email protected] on 24 Sep 2012 at 6:26

on x86_64 Ubuntu 22.04 VM @ addr
ffffffffc0000000

Need to check...

File open on /sys/kernel/debug/devmem_rw/get_page_offset fails, even as root!
Error : "rdmem: open dbgfs_file: Operation not permitted"
errno=EPERM.

Weird:
Fails: on x86_64 native Ubuntu 18.10, fails on Fedora 29 guest.
(I tried disabling any active LSMs - AppArmor, SELinux. No luck).
Works: on x86_64 18.04 LTS guest VM, on ARMv7 Raspberry Pi