selftests/bpf: Fix size calculation in bpf_xdp_pull_data

The test employs 'sizeof(struct xdp_frame)' on the BPF side, which is not
portable and results in test failures when run on 32-bit systems:

  root@qemu-armhf:/usr/libexec/kselftests-bpf# test_progs -a xdp_pull_data
  [...]
  run_test:PASS:calloc buf 0 nsec
  run_test:PASS:bpf_prog_test_run_opts 0 nsec
  run_test:FAIL:xdp_pull_data_prog retval unexpected xdp_pull_data_prog retval: actual 2 != expected 1
  run_test:PASS:calloc buf 0 nsec
  run_test:PASS:bpf_prog_test_run_opts 0 nsec
  run_test:FAIL:xdp_pull_data_prog retval unexpected xdp_pull_data_prog retval: actual 2 != expected 1
  run_test:PASS:calloc buf 0 nsec
  run_test:PASS:bpf_prog_test_run_opts 0 nsec
  run_test:FAIL:xdp_pull_data_prog retval unexpected xdp_pull_data_prog retval: actual 2 != expected 1
  run_test:PASS:calloc buf 0 nsec
  run_test:PASS:bpf_prog_test_run_opts 0 nsec
  run_test:FAIL:xdp_pull_data_prog retval unexpected xdp_pull_data_prog retval: actual 2 != expected 1
  #639/1   xdp_pull_data/xdp_pull_data:FAIL

Fix by using 'bpf_core_type_size(struct xdp_frame)' instead.

Fixes: 323302f ("selftests/bpf: Test bpf_xdp_pull_data")
Signed-off-by: Tony Ambardar <[email protected]>

Author: guidosarducci

tools/testing/selftests/bpf/progs/test_xdp_pull_data.c

@@ -2,6 +2,7 @@
 
 #include "vmlinux.h"
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
 
 int xdpf_sz;
 int sinfo_sz;
@@ -13,7 +14,7 @@ int pull_len;
 SEC("xdp.frags")
 int xdp_find_sizes(struct xdp_md *ctx)
 {
-	xdpf_sz = sizeof(struct xdp_frame);
+	xdpf_sz = bpf_core_type_size(struct xdp_frame);
 	sinfo_sz = __PAGE_SIZE - XDP_PACKET_HEADROOM -
 		   (ctx->data_end - ctx->data);