selftests/bpf: Fix endianness issues in atomic tests

Atomic tests store a DW, but then load it back as a W from the same
address. This doesn't work on big-endian systems, and since the point
of those tests is not testing narrow loads, fix simply by loading a
DW.

Fixes: 98d666d ("bpf: Add tests for new BPF atomic operations")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210210020713.77911-1-iii@linux.ibm.com

tools/testing/selftests/bpf/verifier/atomic_and.c

@@ -7,7 +7,7 @@
 		BPF_MOV64_IMM(BPF_REG_1, 0x011),
 		BPF_ATOMIC_OP(BPF_DW, BPF_AND, BPF_REG_10, BPF_REG_1, -8),
 		/* if (val != 0x010) exit(2); */
-		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -8),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
 		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0x010, 2),
 		BPF_MOV64_IMM(BPF_REG_0, 2),
 		BPF_EXIT_INSN(),

tools/testing/selftests/bpf/verifier/atomic_or.c

@@ -7,7 +7,7 @@
 		BPF_MOV64_IMM(BPF_REG_1, 0x011),
 		BPF_ATOMIC_OP(BPF_DW, BPF_OR, BPF_REG_10, BPF_REG_1, -8),
 		/* if (val != 0x111) exit(2); */
-		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -8),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
 		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0x111, 2),
 		BPF_MOV64_IMM(BPF_REG_0, 2),
 		BPF_EXIT_INSN(),

tools/testing/selftests/bpf/verifier/atomic_xor.c

@@ -7,7 +7,7 @@
 		BPF_MOV64_IMM(BPF_REG_1, 0x011),
 		BPF_ATOMIC_OP(BPF_DW, BPF_XOR, BPF_REG_10, BPF_REG_1, -8),
 		/* if (val != 0x101) exit(2); */
-		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -8),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
 		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0x101, 2),
 		BPF_MOV64_IMM(BPF_REG_0, 2),
 		BPF_EXIT_INSN(),