Re: [PATCH v3 3/5] tools/libs/foreignmemory: Fix PAGE_SIZE redefinition error

[Julien Grall <julien@xen.org>]

Hi Costin,

On 10/05/2021 09:35, Costin Lupu wrote:
> @@ -168,7 +168,7 @@ void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
>       size_t i;
>       int rc;
>   
> -    addr = mmap(addr, num << PAGE_SHIFT, prot, flags | MAP_SHARED,
> +    addr = mmap(addr, num << XC_PAGE_SHIFT, prot, flags | MAP_SHARED,
>                   fd, 0);
>       if ( addr == MAP_FAILED )
>           return NULL;
> @@ -198,9 +198,10 @@ void *osdep_xenforeignmemory_map(xenforeignmemory_handle *fmem,
>            */
>           privcmd_mmapbatch_t ioctlx;
>           xen_pfn_t *pfn;
> -        unsigned int pfn_arr_size = ROUNDUP((num * sizeof(*pfn)), PAGE_SHIFT);
> +        unsigned int pfn_arr_size = ROUNDUP((num * sizeof(*pfn)), XC_PAGE_SHIFT);
> +        int os_page_size = getpagesize();

Hmmm... Sorry I only realized now that the manpage suggests that 
getpagesize() is legacy:

     SVr4, 4.4BSD, SUSv2.  In SUSv2 the getpagesize() call is labeled 
LEGACY, and in POSIX.1-2001 it has been dropped; HP-UX does not have 
this call.

And then:

    Portable applications should employ sysconf(_SC_PAGESIZE) instead of 
getpagesize():

            #include <unistd.h>
            long sz = sysconf(_SC_PAGESIZE);

As this is only used by Linux, it is not clear to me whether this is 
important. Ian, what do you think?

>   
> -        if ( pfn_arr_size <= PAGE_SIZE )
> +        if ( pfn_arr_size <= os_page_size )

Your commit message suggests we are only s/PAGE_SHIFT/XC_PAGE_SHIFT/ but 
this is using getpagesize() instead. I agree it should be using the OS 
size. However, this should be clarified in the commit message.

The rest of the patch looks fine to me .

Cheers,

-- 
Julien Grall