selftests/bpf: Range analysis test case for JSET

This patch adds coverage for the warning detected by syzkaller and fixed
in the previous patch. Without the previous patch, this test fails with:

verifier bug: REG INVARIANTS VIOLATION (false_reg1): range bounds
violation u64=[0x0, 0x0] s64=[0x0, 0x0] u32=[0x1, 0x0] s32=[0x0, 0x0]
var_off=(0x0, 0x0)(1)

Signed-off-by: Paul Chaignon <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Link: https://lore.kernel.org/r/c7893[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 /* Converted from tools/testing/selftests/bpf/verifier/bounds.c */
 
 #include <linux/bpf.h>
+#include <../../../include/linux/filter.h>
 #include <bpf/bpf_helpers.h>
 #include "bpf_misc.h"
 
···
 	"exit"
 	:
 	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("dead branch on jset, does not result in invariants violation error")
+__success __log_level(2)
+__retval(0) __flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_range_analysis(void)
+{
+	asm volatile ("			\
+	call %[bpf_get_netns_cookie];	\
+	if r0 == 0 goto l0_%=;		\
+	if r0 & 0xffffffff goto +0; 	\
+l0_%=:	r0 = 0;				\
+	exit;				\
+"	:
+	: __imm(bpf_get_netns_cookie)
 	: __clobber_all);
 }