[PATCH v17 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel

[Catalin Marinas]

On Wed, Jun 12, 2019 at 01:30:36PM +0100, Szabolcs Nagy wrote:
> On 12/06/2019 12:43, Andrey Konovalov wrote:
> > --- /dev/null
> > +++ b/tools/testing/selftests/arm64/tags_lib.c
> > @@ -0,0 +1,62 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <stdlib.h>
> > +#include <sys/prctl.h>
> > +
> > +#define TAG_SHIFT	(56)
> > +#define TAG_MASK	(0xffUL << TAG_SHIFT)
> > +
> > +#define PR_SET_TAGGED_ADDR_CTRL	55
> > +#define PR_GET_TAGGED_ADDR_CTRL	56
> > +#define PR_TAGGED_ADDR_ENABLE	(1UL << 0)
> > +
> > +void *__libc_malloc(size_t size);
> > +void __libc_free(void *ptr);
> > +void *__libc_realloc(void *ptr, size_t size);
> > +void *__libc_calloc(size_t nmemb, size_t size);
> 
> this does not work on at least musl.
> 
> the most robust solution would be to implement
> the malloc apis with mmap/munmap/mremap, if that's
> too cumbersome then use dlsym RTLD_NEXT (although
> that has the slight wart that in glibc it may call
> calloc so wrapping calloc that way is tricky).
> 
> in simple linux tests i'd just use static or
> stack allocations or mmap.
> 
> if a generic preloadable lib solution is needed
> then do it properly with pthread_once to avoid
> races etc.

Thanks for the feedback Szabolcs. I guess we can go back to the initial
simple test that Andrey had and drop the whole LD_PRELOAD hack (I'll
just use it for my internal testing).

BTW, when you get some time, please review Vincenzo's ABI documentation
patches from a user/libc perspective. Once agreed, they should become
part of this series.

-- 
Catalin