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

[Andrey Konovalov]

On Wed, Jun 12, 2019 at 5:01 PM Catalin Marinas <catalin.marinas at arm.com> wrote:
>
> 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).

OK, will do in v18.

>
> 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