On Mon, May 06, 2013 at 09:57:01PM +0200, Andrea Arcangeli wrote:
> ===
>
> static unsigned char *c, *tmp;
>
> void userfault_sighandler(int signum, siginfo_t *info, void *ctx)
oops, the hash of the test program got cut... so I append it below
which is nicer without leading whitespaces.
===
#define _GNU_SOURCE
#include <sys/mman.h>
#include <pthread.h>
#include <strings.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <sys/syscall.h>
#include <sys/types.h>
#define USE_USERFAULT
#define THP
#define MADV_USERFAULT 18
#define SIZE (1024*1024*1024)
#define SYS_remap_anon_pages 314
static unsigned char *c, *tmp;
void userfault_sighandler(int signum, siginfo_t *info, void *ctx)
{
unsigned char *addr = info->si_addr;
int len = 4096;
int ret;
#ifdef THP
addr = (unsigned char *) ((unsigned long) addr & ~((2*1024*1024)-1));
len = 2*1024*1024;
#endif
if (addr >= c && addr < c + SIZE) {
unsigned long offset = addr - c;
ret = syscall(SYS_remap_anon_pages, c+offset, tmp+offset, len);
if (ret)
perror("sigbus remap_anon_pages"), exit(1);
//printf("sigbus offset %lu\n", offset);
return;
}
printf("sigbus error addr %p c %p tmp %p\n", addr, c, tmp), exit(1);
}
int main()
{
struct sigaction sa;
int ret;
unsigned long i;
#ifndef THP
/*
* Fails with THP due lack of alignment because of memset
* pre-filling the destination
*/
c = mmap(0, SIZE, PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
if (c == MAP_FAILED)
perror("mmap"), exit(1);
tmp = mmap(0, SIZE, PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
if (tmp == MAP_FAILED)
perror("mmap"), exit(1);
#else
ret = posix_memalign((void **)&c, 2*1024*1024, SIZE);
if (ret)
perror("posix_memalign"), exit(1);
ret = posix_memalign((void **)&tmp, 2*1024*1024, SIZE);
if (ret)
perror("posix_memalign"), exit(1);
#endif
/*
* MADV_USERFAULT must run before memset, to avoid THP 2m
* faults to map memory into "tmp", if "tmp" isn't allocated
* with hugepage alignment.
*/
if (madvise(c, SIZE, MADV_USERFAULT))
perror("madvise"), exit(1);
memset(tmp, 0xaa, SIZE);
sa.sa_sigaction = userfault_sighandler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO;
sigaction(SIGBUS, &sa, NULL);
#ifndef USE_USERFAULT
ret = syscall(SYS_remap_anon_pages, c, tmp, SIZE);
if (ret)
perror("remap_anon_pages"), exit(1);
#endif
for (i = 0; i < SIZE; i += 4096) {
if ((i/4096) % 2) {
/* exercise read and write MADV_USERFAULT */
c[i+1] = 0xbb;
}
if (c[i] != 0xaa)
printf("error %x offset %lu\n", c[i], i), exit(1);
}
return 0;
}
--
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