[CRIU] [PATCH v3] compel/ppc64le: make task size detection more robust

[Andrei Vagin]

On Thu, Sep 07, 2017 at 11:41:59AM +0300, Mike Rapoport wrote:
> The recent changes to user address space limits in the Linux kernel break
> the assumption that TASK_SIZE is 128TB. For now, the maximal task size on
> ppc64le is 512TB and we need to detect it in runtime for compatibility with
> older kernels.
> 
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> Acked-by: Laurent Dufour <ldufour at linux.vnet.ibm.com>
> ---
> v3: drop unused definition of TASK_SIZE_128TB
> v2: fix off-by-one
> 
>  compel/arch/ppc64/src/lib/infect.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/compel/arch/ppc64/src/lib/infect.c b/compel/arch/ppc64/src/lib/infect.c
> index 8112588..1fa333e 100644
> --- a/compel/arch/ppc64/src/lib/infect.c
> +++ b/compel/arch/ppc64/src/lib/infect.c
> @@ -2,6 +2,7 @@
>  #include <sys/types.h>
>  #include <sys/uio.h>
>  #include <sys/user.h>
> +#include <sys/mman.h>
>  #include <stdint.h>
>  #include <errno.h>
>  #include <compel/plugins/std/syscall-codes.h>
> @@ -9,6 +10,7 @@
>  #include "errno.h"
>  #include "log.h"
>  #include "common/bug.h"
> +#include "common/page.h"
>  #include "infect.h"
>  #include "infect-priv.h"
>  
> @@ -458,7 +460,18 @@ int arch_fetch_sas(struct parasite_ctl *ctl, struct rt_sigframe *s)
>   *
>   * NOTE: 32bit tasks are not supported.
>   */
> -#define TASK_SIZE_USER64	(0x0000400000000000UL)
> -#define TASK_SIZE		TASK_SIZE_USER64
> +#define TASK_SIZE_64TB  (0x0000400000000000UL)
> +#define TASK_SIZE_512TB (0x0002000000000000UL)
>  
> -unsigned long compel_task_size(void) { return TASK_SIZE; }
> +#define TASK_SIZE_MIN TASK_SIZE_64TB
> +#define TASK_SIZE_MAX TASK_SIZE_512TB
> +
> +unsigned long compel_task_size(void)
> +{
> +	unsigned long task_size;
> +
> +	for (task_size = TASK_SIZE_MIN; task_size < TASK_SIZE_MAX; task_size <<= 1)
> +		if (munmap((void *)task_size, page_size()))

What if you unmap something useful?

> +			break;
> +	return task_size;
> +}
> -- 
> 2.7.4
>