[CRIU] [PATCH 04/13] mem: Add read_pme helper

[Pavel Emelyanov]

On 05/22/2013 11:09 PM, Cyrill Gorcunov wrote:
> 
> Will need it to compare page frame number of vdso areas.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  include/mem.h |  3 +++
>  mem.c         | 29 +++++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+)
> 
> +int read_pme(pid_t pid, unsigned long addr, u64 *pme)
> +{
> +	int fd, ret = -1;
> +	char path[32];
> +	off_t off;
> +
> +	snprintf(path, sizeof(path), "/proc/%d/pagemap", pid);

Can we use existing open_proc helper?

> +	fd = open(path, O_RDONLY);

Can we open this file once during parasite_fixup_vdso()?

> +	if (fd < 0) {
> +		pr_perror("Can't open %s", path);
> +		return -1;
> +	}
> +
> +	off = (addr / PAGE_SIZE) * sizeof(u64);
> +	if (lseek(fd, off, SEEK_SET) != off) {
> +		pr_perror("Failed to seek address %lx\n", addr);
> +		goto out;
> +	}
> +
> +	ret = read(fd, pme, sizeof(*pme));
> +	if (ret < 0) {
> +		pr_perror("Can't read pme for pid %d", pid);
> +		goto out;
> +	}
> +	ret = 0;
> +out:
> +	close(fd);
> +	return ret;
> +}