Re: disk_map in subr_disk.c
On Wed, Jul 25, 2012 at 11:37:32PM +0200, Frank Brodbeck wrote:
On Wed, Jul 25, 2012 at 10:51:56PM +0200, Otto Moerbeek wrote:
Userland prorams do not share memory or symbols with the kernel at all
that is a fundamental thing in Unix. Your code just references a bunch
of uninitialized vars.
Chekc opendev(3) (source in src/lib/libutil/opendev.c) which is a
userland function to do the translation you want. Note it interfaces
with the kernel via ioctl(2), the actual work is done by the diskmap
device driver that calls disk_map(), all in kernel mode.
Funny, I first looked at opendev(3) and the DIOCMAP ioctl before I went
on to disk_map(). Obviously I missed something. Will have a look at
opendev(3) again.
Thanks a lot for the pointer.
Frank.
Maybe this helps:
#include sys/types.h
#include sys/dkio.h
#include sys/disk.h
#include sys/ioctl.h
#include err.h
#include fcntl.h
#include limits.h
#include stdio.h
#include stdlib.h
#include string.h
#include unistd.h
int
main(int argc, char *argv[])
{
struct dk_diskmap dm;
const char *dmpath = /dev/diskmap;
char dev[PATH_MAX];
char *d;
if (argc != 2) {
fprintf(stderr, usage: duid2dev duid|device\n);
exit(1);
}
bzero(dm, sizeof(dm));
dm.flags = DM_OPENPART;
if ((dm.fd = open(dmpath, O_RDONLY)) 0)
err(1, open: %s, dmpath);
strlcpy(dev, argv[1], PATH_MAX);
dm.device = dev;
if (ioctl(dm.fd, DIOCMAP, dm) == -1)
err(1, ioctl);
d = strrchr(dm.device, '/');
if (d[1] == 'r')
dm.device = d + 2;
else
dm.device = d + 1;
dm.device[strlen(dm.device) - 1] = '\0';
printf(%s\n, dm.device);
close(dm.fd);
exit(0);
}
--
Frank Brodbeck f...@guug.de
Re: disk_map in subr_disk.c
On Wed, Jul 25, 2012 at 09:34:02PM +0200, Frank Brodbeck wrote: | Hi, | | currently I am trying (just out of curiosity) to find a way to resolve a | duid to a device name. For that matter I believe that looking at | disk_map() in subr_disk.c is the right place. Or try sysctl(3). Here's some output from sysctl(8): hw.disknames=sd0:3e482244f831fa23,cd0: Paul 'WEiRD' de Weerd -- [++-]+++.+++[---].+++[+ +++-].++[-]+.--.[-] http://www.weirdnet.nl/
disk_map in subr_disk.c
Hi,
currently I am trying (just out of curiosity) to find a way to resolve a
duid to a device name. For that matter I believe that looking at
disk_map() in subr_disk.c is the right place.
As I am a complete C beginner I have a hard time to understand a
particular block of code so I decided to copy that function into my own
C code so I can easily track what's going on w/ gdb:
int
main(void)
{
struct disk *dk, *mdk;
struct disklist_head disklist;
u_char uid[8];
char *path, *mpath, part, c;
int i;
path = 9c750dc043a2751f.i;
part = path[17];
bzero(uid, sizeof(uid));
for (i = 0; i 16; i++) {
c = path[i];
if (c = '0' c = '9')
c -= '0';
else if (c = 'a' c = 'f')
c -= ('a' - 10);
else
errx(Invalid duid);
uid[i / 2] = 4;
uid[i / 2] |= c 0xf;
}
mdk = NULL;
TAILQ_FOREACH(dk, disklist, dk_link) {
if ((dk-dk_flags DKF_LABELVALID) dk-dk_label
bcmp(dk-dk_label-d_uid, uid,
sizeof(dk-dk_label-d_uid)) == 0) {
if (mdk != NULL)
return -1;
mdk = dk;
}
}
return 0;
}
If I run the program I get a segfault and w/ gdb I see:
Program received signal SIGSEGV, Segmentation fault.
bcmp (b1=0x1c7f88988, b2=0x7f7be830, length=8) at
/usr/src/lib/libc/string/bcmp.c:51
Which I believe is caused by dk-dk_label-d_uid being inaccessible:
(gdb) print dk-dk_label
$1 = (struct disklabel *) 0x1c7f88948
(gdb) print dk-dk_label-d_uid
Cannot access memory at address 0x1c7f88988
In dev/diskmap.c I see copyinstr(9) before disk_map() and copyoutstr(9)
after disk_map. Is this because dk-dk_label-d_uid is not accessible
from userspace or am I talking complete BS here?
Beatings with the cluestick are welcomed.
Thanks,
Frank.
--
Frank Brodbeck f...@guug.de
Re: disk_map in subr_disk.c
On Wed, Jul 25, 2012 at 09:34:02PM +0200, Frank Brodbeck wrote:
Hi,
currently I am trying (just out of curiosity) to find a way to resolve a
duid to a device name. For that matter I believe that looking at
disk_map() in subr_disk.c is the right place.
As I am a complete C beginner I have a hard time to understand a
particular block of code so I decided to copy that function into my own
C code so I can easily track what's going on w/ gdb:
int
main(void)
{
struct disk *dk, *mdk;
struct disklist_head disklist;
u_char uid[8];
char *path, *mpath, part, c;
int i;
path = 9c750dc043a2751f.i;
part = path[17];
bzero(uid, sizeof(uid));
for (i = 0; i 16; i++) {
c = path[i];
if (c = '0' c = '9')
c -= '0';
else if (c = 'a' c = 'f')
c -= ('a' - 10);
else
errx(Invalid duid);
uid[i / 2] = 4;
uid[i / 2] |= c 0xf;
}
mdk = NULL;
TAILQ_FOREACH(dk, disklist, dk_link) {
if ((dk-dk_flags DKF_LABELVALID) dk-dk_label
bcmp(dk-dk_label-d_uid, uid,
sizeof(dk-dk_label-d_uid)) == 0) {
if (mdk != NULL)
return -1;
mdk = dk;
}
}
return 0;
}
If I run the program I get a segfault and w/ gdb I see:
Program received signal SIGSEGV, Segmentation fault.
bcmp (b1=0x1c7f88988, b2=0x7f7be830, length=8) at
/usr/src/lib/libc/string/bcmp.c:51
Which I believe is caused by dk-dk_label-d_uid being inaccessible:
(gdb) print dk-dk_label
$1 = (struct disklabel *) 0x1c7f88948
(gdb) print dk-dk_label-d_uid
Cannot access memory at address 0x1c7f88988
In dev/diskmap.c I see copyinstr(9) before disk_map() and copyoutstr(9)
after disk_map. Is this because dk-dk_label-d_uid is not accessible
from userspace or am I talking complete BS here?
Userland prorams do not share memory or symbols with the kernel at all
that is a fundamental thing in Unix. Your code just references a bunch
of uninitialized vars.
Chekc opendev(3) (source in src/lib/libutil/opendev.c) which is a
userland function to do the translation you want. Note it interfaces
with the kernel via ioctl(2), the actual work is done by the diskmap
device driver that calls disk_map(), all in kernel mode.
-Otto
Re: disk_map in subr_disk.c
On Wed, Jul 25, 2012 at 10:51:56PM +0200, Otto Moerbeek wrote: Userland prorams do not share memory or symbols with the kernel at all that is a fundamental thing in Unix. Your code just references a bunch of uninitialized vars. Chekc opendev(3) (source in src/lib/libutil/opendev.c) which is a userland function to do the translation you want. Note it interfaces with the kernel via ioctl(2), the actual work is done by the diskmap device driver that calls disk_map(), all in kernel mode. Funny, I first looked at opendev(3) and the DIOCMAP ioctl before I went on to disk_map(). Obviously I missed something. Will have a look at opendev(3) again. Thanks a lot for the pointer. Frank. -- Frank Brodbeck f...@guug.de
