On Mon, 2010-08-30 at 22:57 -0600, dann frazier wrote:
> On Mon, Aug 30, 2010 at 08:22:23AM -0600, dann frazier wrote:
> > hey Ian,
> > I haven't seen any reports of xen problems w/ the latest lenny DSA
> > that added the guard page code. I looked at backporting the 3 patches
> > from Linus - but the mlock patch touches code that didn't exist in
> > .26, so I'm wondering if that patch is just not needed.
>
> fyi, I setup a Xen/lenny system and didn't have any problems w/
> save/restore, so we're good afaict :)
Thanks, I can't see code in the Lenny kernel equivalent to that which
was broken either.
I wrote a pretty skanky test program to test for the issue (mlock.c,
attached, run with "./mlock lock" to trigger the issue). I don't have a
Lenny system to hand right not where I can run it but if you still have
a Lenny system setup then it might be interesting to try. (the test
program doesn't actually require Xen to demonstrate the issue so any
Lenny system should do).
Ian.
--
Ian Campbell
Current Noise: Desecration - Human Gore
Barach's Rule:
An alcoholic is a person who drinks more than his own physician.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/resource.h>
#define PAGE_SIZE 4096
#define PAGE_MASK (~(PAGE_SIZE-1))
static void do_lock(void *addr, size_t len)
{
void *laddr = (void *)((unsigned long)addr & PAGE_MASK);
size_t llen = (len + ((unsigned long)addr - (unsigned long)laddr) +
PAGE_SIZE - 1) & PAGE_MASK;
int e = mlock(laddr, llen);
printf("locking %p-%p -> %p-%p -> %d\n",
addr, addr+len, laddr, laddr+llen, e);
if (e < 0)
exit(1);
}
static void do_test(int lock_it) __attribute__((noinline));
static void do_test(int lock_it) {
struct rusage rbefore, rafter;
struct {
char pad1[2*PAGE_SIZE];
unsigned long lock_me;
char pad2[2*PAGE_SIZE];
} s;
unsigned long esp;
s.pad1[0] = 1;
s.pad2[2*PAGE_SIZE-1] = 1;
//memset(&s.pad1, 0, sizeof(s.pad1));
//memset(&s.pad2, 0, sizeof(s.pad2));
printf("pad1 at %p-%p\n", &s.pad1[0], &s.pad1[sizeof(s.pad1)-1]);
printf("LCK at %p-%p\n", &s.lock_me, &s.lock_me + 1);
printf("pad2 at %p-%p\n", &s.pad2[0], &s.pad2[sizeof(s.pad2)-1]);
asm volatile("mov %%esp, %0\n" : "=r" (esp));
printf("esp: %#lx\n", esp);
if (lock_it) {
do_lock(&s.lock_me, sizeof(s.lock_me));
}
getrusage(RUSAGE_SELF, &rbefore);
s.lock_me = 0xdeadbeef;
getrusage(RUSAGE_SELF, &rafter);
printf("minor faults: %ld -> %ld\n", rbefore.ru_minflt, rafter.ru_minflt);
printf("major faults: %ld -> %ld\n", rbefore.ru_majflt, rafter.ru_majflt);
if (lock_it && (rbefore.ru_minflt != rafter.ru_minflt || rbefore.ru_majflt != rafter.ru_majflt))
printf("ERROR -- Should not have faulted\n");
}
int main(int argc, char **argv)
{
do_test(argc > 1 && strcmp(argv[1], "lock") == 0);
return 0;
}
