[PATCH bpf-next 2/2] selftests/bpf: Add a couple of tests for potential sdiv overflow

[Yonghong Song <yonghong.song@linux.dev>]

Two subtests are added to exercise the patched code which handles
LLONG_MIN/-1. The first subtest will cause kernel exception without
previous kernel verifier change. The second subtest exercises part
of the patched code logic and the end result is still correct.

Translated asm codes are parts of correctness checking and those asm
codes also make it easy to understand the patched code in verifier.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 .../selftests/bpf/progs/verifier_sdiv.c       | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_sdiv.c b/tools/testing/selftests/bpf/progs/verifier_sdiv.c
index 2a2271cf0294..c9c56008e534 100644
--- a/tools/testing/selftests/bpf/progs/verifier_sdiv.c
+++ b/tools/testing/selftests/bpf/progs/verifier_sdiv.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/bpf.h>
+#include <limits.h>
 #include <bpf/bpf_helpers.h>
 #include "bpf_misc.h"
 
@@ -770,6 +771,74 @@ __naked void smod64_zero_divisor(void)
 "	::: __clobber_all);
 }
 
+SEC("socket")
+__description("SDIV64, overflow, LLONG_MIN/-1")
+__success __retval(1)
+__arch_x86_64
+__xlated("0: r2 = 0x8000000000000000")
+__xlated("2: r3 = -1")
+__xlated("3: r4 = r2")
+__xlated("4: if r3 != 0x0 goto pc+2")
+__xlated("5: w2 ^= w2")
+__xlated("6: goto pc+8")
+__xlated("7: if r3 != 0xffffffff goto pc+6")
+__xlated("8: r3 = 0x8000000000000000")
+__xlated("10: if r2 != r3 goto pc+2")
+__xlated("11: r3 = -1")
+__xlated("12: goto pc+2")
+__xlated("13: r3 = -1")
+__xlated("14: r2 s/= r3")
+__xlated("15: r0 = 0")
+__xlated("16: if r2 != r4 goto pc+1")
+__xlated("17: r0 = 1")
+__xlated("18: exit")
+__naked void sdiv64_overflow(void)
+{
+	asm volatile ("					\
+	r2 = %[llong_min] ll;				\
+	r3 = -1;					\
+	r4 = r2;					\
+	r2 s/= r3;					\
+	r0 = 0;						\
+	if r2 != r4 goto +1;				\
+	r0 = 1;						\
+	exit;						\
+"	:
+	: __imm_const(llong_min, LLONG_MIN)
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SDIV64, divisor -1")
+__success __retval(-5)
+__arch_x86_64
+__xlated("0: r2 = 5")
+__xlated("1: r3 = -1")
+__xlated("2: if r3 != 0x0 goto pc+2")
+__xlated("3: w2 ^= w2")
+__xlated("4: goto pc+8")
+__xlated("5: if r3 != 0xffffffff goto pc+6")
+__xlated("6: r3 = 0x8000000000000000")
+__xlated("8: if r2 != r3 goto pc+2")
+__xlated("9: r3 = -1")
+__xlated("10: goto pc+2")
+__xlated("11: r3 = -1")
+__xlated("12: r2 s/= r3")
+__xlated("13: r0 = r2")
+__xlated("14: exit")
+__naked void sdiv64_divisor_neg_1(void)
+{
+	asm volatile ("					\
+	r2 = 5;						\
+	r3 = -1;					\
+	r2 s/= r3;					\
+	r0 = r2;					\
+	exit;						\
+"	:
+	: __imm_const(llong_min, LLONG_MIN)
+	: __clobber_all);
+}
+
 #else
 
 SEC("socket")
-- 
2.43.5