On 10/21/2010 09:19 AM, David Daney wrote:
On 10/20/2010 02:31 PM, Camm Maguire wrote:
Greetings!
Does this suffice?
(sid)camm@gabrielli:~/maxima-5.22.1/tests$ uname -a
Linux gabrielli 2.6.35.4-dsa-octeon #1 SMP Fri Sep 17 21:15:34 UTC
2010 mips64 GNU/Linux
(sid)camm@gabrielli:~/maxima-5.22.1/tests$ cat /proc/cpuinfo
system type : CUST_WSX16 (CN3860p3.X-500-EXP)
processor : 0
cpu model : Cavium Octeon V0.3
[...]
Hah! I have those things piled up all around me.
No guarantees, but I will try to reproduce it. If I can reproduce it, it
should be easy to fix.
Definitely a kernel bug. Consider this program:
------------8<--------sigbus.c-------
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
int main(int argc, char *argv[])
{
int pgsize;
float *p1;
float *p2;
int r;
pgsize = getpagesize();
p1 = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (p1 == MAP_FAILED) {
perror("mmap p1 failed");
exit(1);
}
p2 = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (p2 == MAP_FAILED) {
perror("mmap p2 failed");
exit(1);
}
*p1 = 2.5;
*p2 = 3.5;
r = mprotect(p1, pgsize, PROT_READ);
if (r) {
perror("mprotect p1 failed");
exit(1);
}
r = mprotect(p2, pgsize, PROT_READ);
if (r) {
perror("mprotect p2 failed");
exit(1);
}
*p2 = *p1;
asm volatile("" ::: "memory");
puts("All done!");
exit(0);
}
------------8<-----------------------
$ mips64-octeon-linux-gnu-gcc -Wall -mhard-float -march=mips64 -O3 -o
sigbus sigbus.c
$ mips64-octeon-linux-gnu-objdump -d sigbus > sigbus.dis
The float copy '*p2 = *p1;' dissassembles as:
120000b30: c6400000 lwc1 $f0,0(s2)
120000b34: e6000000 swc1 $f0,0(s0)
When run on an FPU-less system I get:
~ # ./sigbus
Bus error
When run on my x86_64 workstation:
$ ./sigbus
Segmentation fault (core dumped)
I will fix this kernel bug.
David Daney
