[parisc-linux] Unaligned trap handler - comments appreciated

[parisc-linux] Unaligned trap handler - comments appreciated

[Randolph Chung]

I just checked in an arch/parisc/kernel/unaligned.c file into palinux
cvs.

It's my (not-yet-successful) attempt at putting together an unaligned
memory access handler for palinux.

Since I'm not really familiar with how this is "supposed" to be done, I
would really appreciate if folks more in the know can review the code
and let me know if i'm on the right track, or if i'm smoking something
funny :-)

I haven't checked in the (simple, obvious) hook in traps.c that calls
the unaligned handler since it isn't working yet.

thanks for your patience :)
randolph
-- 
   @..@                                         http://www.TauSq.org/
  (----)
 ( >__< )
 ^^ ~~ ^^

Re: [parisc-linux] Unaligned trap handler - comments appreciated

[Randolph Chung]

In reference to a message from Randolph Chung, dated Jun 18:
> I just checked in an arch/parisc/kernel/unaligned.c file into palinux
> cvs.

I've updated traps.c to call the unaligned handler now. Many thanks to
jsm for his help and advice.

I've only tested this for parisc64, would appreciate if someone can test
to make sure it works on a narrow kernel as well. My test case looks
something like this:


#include <stdio.h>

struct data_t {
        unsigned long a;
        unsigned long b;
};

int main(int argc, char **argv)
{
        struct data_t data;
        unsigned char *t;
        unsigned long l;
        int i;

        data.a = 0x12345678;
        data.b = 0x87654321;

        t = (unsigned char *)(&data)+1;
        l = *((unsigned long *)t);
        printf("l = 0x%08lx\n\n\n", l);

        printf("expected result is: 0x");
        for (i = 0; i < sizeof(unsigned long); i++)
                printf("%x", *(t+i));
        printf("\n");

        printf("testing store...\n");
        *((unsigned long *)t) = 0x13572468;

        l = *((unsigned long *)t);
        printf("l = 0x%08lx\n", l);

        return 0;
}

randolph
-- 
   @..@                                         http://www.TauSq.org/
  (----)
 ( >__< )
 ^^ ~~ ^^

Re: [parisc-linux] Unaligned trap handler - comments appreciated

[Helge Deller]

Hi Randolph,

I've tested your changes on a 32bit kernel:

c3000:~/unaligned# uname -a
Linux c3000 2.4.0-pa37 #1 Sam Jun 23 11:42:43 CEST 2001 parisc unknown
c3000:~/unaligned# gcc unaligned.c
c3000:~/unaligned# ./a.out
Bus error

In the syslog:
Jun 23 14:26:36 c3000 kernel: a.out(3225): unaligned access to 0xbff00649 at 
ip=0x000104fb

Greetings,
Helge

On Saturday 23 June 2001 08:54, Randolph Chung wrote:
> In reference to a message from Randolph Chung, dated Jun 18:
> > I just checked in an arch/parisc/kernel/unaligned.c file into palinux
> > cvs.
>
> I've updated traps.c to call the unaligned handler now. Many thanks to
> jsm for his help and advice.
>
> I've only tested this for parisc64, would appreciate if someone can test
> to make sure it works on a narrow kernel as well. My test case looks
> something like this:
>
>
> #include <stdio.h>
>
> struct data_t {
>         unsigned long a;
>         unsigned long b;
> };
>
> int main(int argc, char **argv)
> {
>         struct data_t data;
>         unsigned char *t;
>         unsigned long l;
>         int i;
>
>         data.a = 0x12345678;
>         data.b = 0x87654321;
>
>         t = (unsigned char *)(&data)+1;
>         l = *((unsigned long *)t);
>         printf("l = 0x%08lx\n\n\n", l);
>
>         printf("expected result is: 0x");
>         for (i = 0; i < sizeof(unsigned long); i++)
>                 printf("%x", *(t+i));
>         printf("\n");
>
>         printf("testing store...\n");
>         *((unsigned long *)t) = 0x13572468;
>
>         l = *((unsigned long *)t);
>         printf("l = 0x%08lx\n", l);
>
>         return 0;
> }
>
> randolph