From: Wenchao Xia <wenchaolinux@xxxxxxxxx>
This serial try to enable mremap syscall to cow some private memory region,
just like what fork() did. As a result, user space application would got a
mirror of those region, and it can be used as a snapshot for further processing.
This patch is based on the commit
a12183c62717ac4579319189a00f5883a18dff08 pulled from upstream (linux 3.9) on
2013-04-04, but I hope to sent it first to see if some case I missed to handle
correctly, will try rebase to latest upstream code in next version.
simple test code:
#define _GNU_SOURCE
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int main(void)
{
int len = 4096 * 2 ;
void *old_addr = malloc(len);
old_addr = ((unsigned long)(old_addr + 4096) & (~0x3FF));
printf("mapping addr %p with len %d.\n", old_addr, len);
char *oldc = old_addr;
oldc[0] = 0;
oldc[1] = 1;
oldc[2] = 2;
oldc[3] = 3;
void *new_addr;
unsigned long new_addr_l;
new_addr = mremap(old_addr, len, 0, 4);
printf("result new addr %lx %p.\n", new_addr_l, new_addr);
char *newc = new_addr;
printf("old value is 0x%lx.\n", *((unsigned long *)oldc));
printf("new value is 0x%lx.\n", *((unsigned long *)newc));
newc[0] = 6;
printf("old value is 0x%lx.\n", *((unsigned long *)oldc));
printf("new value is 0x%lx.\n", *((unsigned long *)newc));
oldc[0] = 9;
printf("old value is 0x%lx.\n", *((unsigned long *)oldc));
printf("new value is 0x%lx.\n", *((unsigned long *)newc));
assert(0 == munmap(new_addr, len));
}
Wenchao Xia (6):
mm: add parameter remove_old in move_huge_pmd()
mm : allow copy between different addresses for copy_one_pte()
mm : export rss vec helper functions
mm : export is_cow_mapping()
mm : add parameter remove_old in move_page_tables
mm : add new option MREMAP_DUP to mremap() syscall
fs/exec.c | 2 +-
include/linux/huge_mm.h | 2 +-
include/linux/mm.h | 9 ++-
include/uapi/linux/mman.h | 1 +
mm/huge_memory.c | 6 +-
mm/memory.c | 33 ++++----
mm/mremap.c | 200 +++++++++++++++++++++++++++++++++++++++++++--
7 files changed, 224 insertions(+), 29 deletions(-)
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