Re: [PATCH] bpf: avoid warning for wrong pointer cast

From: David Miller
Date: Mon Apr 18 2016 - 00:04:21 EST

From: Arnd Bergmann <arnd@xxxxxxxx>
Date: Sat, 16 Apr 2016 22:29:33 +0200

> Two new functions in bpf contain a cast from a 'u64' to a
> pointer. This works on 64-bit architectures but causes a warning
> on all 32-bit architectures:
> kernel/trace/bpf_trace.c: In function 'bpf_perf_event_output_tp':
> kernel/trace/bpf_trace.c:350:13: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> u64 ctx = *(long *)r1;
> This changes the cast to first convert the u64 argument into a uintptr_t,
> which is guaranteed to be the same size as a pointer.
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Fixes: 9940d67c93b5 ("bpf: support bpf_get_stackid() and bpf_perf_event_output() in tracepoint programs")