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 <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/c7893be1170fdbcf64e0200c110cdbd360ce7086.1752171365.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: pchaigno

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

@@ -2,6 +2,7 @@
 /* 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"
 
@@ -1532,4 +1533,21 @@ __naked void sub32_partial_overflow(void)
 	: __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);
+}
+
 char _license[] SEC("license") = "GPL";