Re: [Xen-devel] [PATCH XEN v6 20/32] tools/libs/foreignmemory: Support err == NULL to map.

["Egger, Christoph" <chegger@xxxxxxxxx>]

On 2015/12/09 13:22, Wei Liu wrote:
> On Thu, Dec 03, 2015 at 11:22:17AM +0000, Ian Campbell wrote:
>> The existing xc_map_foreign_bulk-like interface encourages callers to
>> miss error checking for partial failure (by forgetting to scan the err
>> array).
>>
>> Add support for passing err==NULL which behaves in a
>> xc_map_foreign_pages-like manner and returns a global error for any
>> failure.
>>
>> While documenting this also clarify the overall behaviour and the
>> behaviour with err!=NULL.
>>
>> With this the compat wrapper of xc_map_foreign_pages() can be
>> simplified.
>>
>> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> ---
>> v6: New
>> ---
>>  tools/libs/foreignmemory/core.c                    | 30 
>> +++++++++++++++++++++-
>>  .../libs/foreignmemory/include/xenforeignmemory.h  | 24 ++++++++++++++---
>>  tools/libxc/xc_foreign_memory.c                    | 22 +---------------
>>  3 files changed, 51 insertions(+), 25 deletions(-)
>>
>> diff --git a/tools/libs/foreignmemory/core.c 
>> b/tools/libs/foreignmemory/core.c
>> index 21dc7ee..91bea55 100644
>> --- a/tools/libs/foreignmemory/core.c
>> +++ b/tools/libs/foreignmemory/core.c
>> @@ -14,6 +14,8 @@
>>   */
>>  
>>  #include <stdlib.h>
>> +#include <assert.h>
>> +#include <errno.h>
>>  
>>  #include "private.h"
>>  
>> @@ -64,7 +66,33 @@ void *xenforeignmemory_map(xenforeignmemory_handle *fmem,
>>                             uint32_t dom, int prot,
>>                             const xen_pfn_t *arr, int *err, size_t num)
>>  {
>> -    return osdep_xenforeignmemory_map(fmem, dom, prot, arr, err, num);
>> +    void *ret;
>> +    int *err_to_free = NULL;
>> +
>> +    if ( err == NULL )
>> +        err = err_to_free = malloc(num * sizeof(int));
>> +
> 
> malloc can fail, which means when user passes in err==NULL there is two
> possible behaviours of this function?

I recommend calloc(num, sizeof(int))

Christoph

Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B


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