I have attempted to write a kernel module that sends a message via CAN but I am
having trouble understanding which level of the socket api I should be using,
and where there may be some documentation or examples of how to use it?
I am on a much older embedded 2.6.31 imx arm kernel, and eventually I
would like to
send this message from within a high res timer triggered ISR.
This is my code, which is hobbled together from internet examples, and kernel
oops is during sock_sendmsg, for now I am just trying to get it do run as part
of the init of the module:
int SendCanTime(struct timespec *tsCurrentTime) {
int s;
struct sockaddr_can addr;
struct can_frame frame;
struct socket *sock;
int thetime = tsCurrentTime->tv_sec;
mm_segment_t oldfs;
oldfs = get_fs();
set_fs(KERNEL_DS);
printk("cantime.ko: Socket 10\n");
if ((s = sock_create(PF_CAN, SOCK_RAW, CAN_RAW, &sock)) < 0) {
printk("cantime.ko: Socket failure\n");
return 1;
}
printk("cantime.ko: Socket 20\n");
memset(&addr, 0, sizeof(addr));
addr.can_family = PF_CAN;
addr.can_ifindex = 2; // This is bad how do I dynamically find it?
printk("cantime.ko: Socket 30");
if (sock->ops->bind(sock, (struct sockaddr *)&addr, sizeof(struct
sockaddr) ) < 0) {
printk("cantime.ko: Bind failure\n");
return 1;
}
printk("cantime.ko: Socket 40\n");
frame.can_id = 0x00050F93 | CAN_EFF_FLAG;
frame.can_dlc = 6;
frame.data[0] = 0x00;
frame.data[1] = 0x02;
memcpy(frame.data+2, &thetime, sizeof(int));
printk("cantime.ko: Socket 50\n");
if (sock_sendmsg(sock,(struct msghdr*)&frame,sizeof(struct
can_frame)) != sizeof(struct can_frame)) {
printk("cantime.ko: Write failure");
return 1;
}
sock_release(sock);
set_fs(oldfs);
return 0;
}
Output:
cantime.ko: Socket 10
cantime.ko: Socket 20
cantime.ko: Socket 30cantime.ko: Socket 40
cantime.ko: Socket 50
Unable to handle kernel paging request at virtual address 80050f93
pgd = d14c8000
[80050f93] *pgd=00000000
Internal error: Oops: 1 [#1] PREEMPT
Modules linked in: cantime(+) g_ether arcotg_udc
CPU: 0 Not tainted (2.6.31-imx-09.12.00 #1)
PC is at raw_sendmsg+0x20/0x138
LR is at sock_sendmsg+0xa0/0xc4
pc : [<c02fe83c>] lr : [<c0283c30>] psr: a0000013
sp : d67fddc8 ip : c04246c4 fp : 00000000
r10: 0000bb38 r9 : d67fc000 r8 : 00000010
r7 : d67fded0 r6 : d679fe00 r5 : 00000000 r4 : 00000000
r3 : 00000010 r2 : 80050f93 r1 : d0d194e0 r0 : d67fdde8
Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: 0005317f Table: 914c8000 DAC: 00000017
Process insmod (pid: 13116, stack limit = 0xd67fc270)
Stack: (0xd67fddc8 to 0xd67fe000)
ddc0: d67fc000 000699b8 00000000 00000000 d67fded0 00000000
dde0: c0044fe4 c0283c30 c031b2a8 d785c4cc 00000000 00000001 ffffffff 00000000
de00: 00000000 00000000 00000000 00000000 d785c340 d67fde20 00000000 00000000
de20: 00002a89 d785c340 c00793d0 d67fde2c d67fde2c c031b278 00000000 00000016
de40: d67fde78 c0398293 d679ff38 d6aaa800 00000034 60000013 00000000 c0044fe4
de60: d6aaa800 0000bb38 00000000 c02feb94 00000000 d0d194e0 d6aaa800 d679fe00
de80: d6aaa800 00000010 d0d194e0 00000000 00000000 d67fded0 00000002 bf000000
dea0: 00000000 c0044fe4 d67fc000 0000bb38 00000000 c031ab78 00000000 d67fdee0
dec0: 00000002 bf000000 00000000 bf01837c 80050f93 bf019506 00000200 bf010000
dee0: 0000001d 00000002 00000000 00000000 00000000 d0d194e0 bf019528 00000000
df00: bf01877b bf0185e8 bf01877b c040e5d0 00000000 00000000 00000000 00000000
df20: 00000000 00000000 bf0188a0 00000000 00000000 00000000 00000000 00000000
df40: 00000000 00000000 00000000 0000003c 00000000 bf0193ac bf0184cc c004432c
df60: 00001e66 bf0193ac 00000000 000c9058 c0044fe4 00000000 bf0193ac 00000000
df80: 000c9058 c008d974 d6bcf6c0 d1477a60 be926ca4 00001e66 be926e67 00000002
dfa0: 00000080 c0044e60 00001e66 be926e67 000c9058 00001e66 000c9008 000c86b8
dfc0: 00001e66 be926e67 00000002 00000080 00000002 0000d33c 0000bb38 00000000
dfe0: be926ca0 be926c90 0001f87c 4001a8d0 20000010 000c9058 00000000 00000000
[<c02fe83c>] (raw_sendmsg+0x20/0x138) from [<c0283c30>] (sock_sendmsg+0xa0/0xc4)
[<c0283c30>] (sock_sendmsg+0xa0/0xc4) from [<bf01837c>]
(SendCanTime+0x10c/0x180 [cantime])
[<bf01837c>] (SendCanTime+0x10c/0x180 [cantime]) from [<bf0185e8>]
(cantime_init+0x11c/0x180 [cantime])
[<bf0185e8>] (cantime_init+0x11c/0x180 [cantime]) from [<c004432c>]
(do_one_initcall+0x5c/0x1c4)
[<c004432c>] (do_one_initcall+0x5c/0x1c4) from [<c008d974>]
(sys_init_module+0xc0/0x1d8)
[<c008d974>] (sys_init_module+0xc0/0x1d8) from [<c0044e60>]
(ret_fast_syscall+0x0/0x2c)
Code: e3520000 e1a08003 e591601c 0a000004 (e1d230b0)
---[ end trace 8599b84226905be0 ]---
I also have the user space code that works perfectly that I was trying to model
my kernel module code after:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <linux/socket.h>
#include <linux/can.h>
#include <linux/can/raw.h>
int main(int argc, char **argv)
{
int s;
struct sockaddr_can addr;
struct ifreq ifr;
struct can_frame frame;
if ((s = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0) {
perror("Socket");
return 1;
}
strcpy(ifr.ifr_name, "can0" );
ioctl(s, SIOCGIFINDEX, &ifr);
memset(&addr, 0, sizeof(addr));
addr.can_family = AF_CAN;
addr.can_ifindex = ifr.ifr_ifindex;
printf("if index = %x\n", addr.can_ifindex);
if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("Bind");
return 1;
}
frame.can_id = 0x00050F93 | CAN_EFF_FLAG;
frame.can_dlc = 6;
frame.data[0] = 0x00;
frame.data[1] = 0x02;
int thetime = (int)time(NULL);
memcpy(frame.data+2, &thetime, sizeof(int));
if (write(s, &frame, sizeof(struct can_frame)) != sizeof(struct can_frame)) {
perror("Write");
return 1;
}
if (close(s) < 0) {
perror("Close");
return 1;
}
return 0;
}
^
