patch 'test/bpf: fix undefined behavior with clang' has been queued to stable release 19.11.11

[christian.ehrhardt at canonical.com]

Hi,

FYI, your patch has been queued to stable release 19.11.11

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before December 10th 2021. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/cpaelzer/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/cpaelzer/dpdk-stable-queue/commit/0f30d115c5cdec4b1dbdda29fedf07a77d3565fd

Thanks.

Christian Ehrhardt <christian.ehrhardt at canonical.com>

---
>From 0f30d115c5cdec4b1dbdda29fedf07a77d3565fd Mon Sep 17 00:00:00 2001
From: Konstantin Ananyev <konstantin.ananyev at intel.com>
Date: Mon, 18 Oct 2021 14:40:52 +0100
Subject: [PATCH] test/bpf: fix undefined behavior with clang

[ upstream commit 3ac2dffae88e8eb5c374b1fdd40d605014526510 ]

test_shift1_check() function fails with clang build.
The reason for that is that clang uses 64-bit shift instruction for
what expected to be 32-bit operation.
To be more specific, this C code:
r2 = (uint32_t)r2 >> r4;
With clang produces:
41a4eb:       48 d3 ef                shr    %cl,%rdi
In that particular case it is an allowed choice, as from one side
left-operand value is known to fit into 32 bits, from other side
according to 'C' standard:
"...if the value of the right operand is negative or is greater than
or equal to the width of the promoted left operand, the behavior is
undefined."
The problem is that on x86 behavior for 64-bit and 32-bit shift
operation might differ.
The fix avoids undefined behavior by making sure
that right operand will not exceed width of the promoted left operand.

Bugzilla ID: 811
Fixes: 9f8f9d91a701 ("test/bpf: introduce functional test")

Reported-by: Stephen Hemminger <stephen at networkplumber.org>
Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
Acked-by: Stephen Hemminger <stephen at networkplumber.org>
---
 app/test/test_bpf.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/app/test/test_bpf.c b/app/test/test_bpf.c
index 88048b4644..533d8ba878 100644
--- a/app/test/test_bpf.c
+++ b/app/test/test_bpf.c
@@ -51,6 +51,9 @@ struct dummy_net {
 #define TEST_SHIFT_1	15
 #define TEST_SHIFT_2	33
 
+#define TEST_SHIFT32_MASK	(CHAR_BIT * sizeof(uint32_t) - 1)
+#define TEST_SHIFT64_MASK	(CHAR_BIT * sizeof(uint64_t) - 1)
+
 #define TEST_JCC_1	0
 #define TEST_JCC_2	-123
 #define TEST_JCC_3	5678
@@ -540,15 +543,25 @@ static const struct ebpf_insn test_shift1_prog[] = {
 		.off = offsetof(struct dummy_vect8, out[1].u64),
 	},
 	{
-		.code = (BPF_ALU | BPF_RSH | BPF_X),
-		.dst_reg = EBPF_REG_2,
-		.src_reg = EBPF_REG_4,
+		.code = (BPF_ALU | BPF_AND | BPF_K),
+		.dst_reg = EBPF_REG_4,
+		.imm = TEST_SHIFT64_MASK,
 	},
 	{
 		.code = (EBPF_ALU64 | BPF_LSH | BPF_X),
 		.dst_reg = EBPF_REG_3,
 		.src_reg = EBPF_REG_4,
 	},
+	{
+		.code = (BPF_ALU | BPF_AND | BPF_K),
+		.dst_reg = EBPF_REG_4,
+		.imm = TEST_SHIFT32_MASK,
+	},
+	{
+		.code = (BPF_ALU | BPF_RSH | BPF_X),
+		.dst_reg = EBPF_REG_2,
+		.src_reg = EBPF_REG_4,
+	},
 	{
 		.code = (BPF_STX | BPF_MEM | EBPF_DW),
 		.dst_reg = EBPF_REG_1,
@@ -582,7 +595,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
 	{
 		.code = (BPF_ALU | BPF_AND | BPF_K),
 		.dst_reg = EBPF_REG_2,
-		.imm = sizeof(uint64_t) * CHAR_BIT - 1,
+		.imm = TEST_SHIFT64_MASK,
 	},
 	{
 		.code = (EBPF_ALU64 | EBPF_ARSH | BPF_X),
@@ -592,7 +605,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
 	{
 		.code = (BPF_ALU | BPF_AND | BPF_K),
 		.dst_reg = EBPF_REG_2,
-		.imm = sizeof(uint32_t) * CHAR_BIT - 1,
+		.imm = TEST_SHIFT32_MASK,
 	},
 	{
 		.code = (BPF_ALU | BPF_LSH | BPF_X),
@@ -658,8 +671,10 @@ test_shift1_check(uint64_t rc, const void *arg)
 	dve.out[0].u64 = r2;
 	dve.out[1].u64 = r3;
 
-	r2 = (uint32_t)r2 >> r4;
+	r4 &= TEST_SHIFT64_MASK;
 	r3 <<= r4;
+	r4 &= TEST_SHIFT32_MASK;
+	r2 = (uint32_t)r2 >> r4;
 
 	dve.out[2].u64 = r2;
 	dve.out[3].u64 = r3;
@@ -668,9 +683,9 @@ test_shift1_check(uint64_t rc, const void *arg)
 	r3 = dvt->in[1].u64;
 	r4 = dvt->in[2].u32;
 
-	r2 &= sizeof(uint64_t) * CHAR_BIT - 1;
+	r2 &= TEST_SHIFT64_MASK;
 	r3 = (int64_t)r3 >> r2;
-	r2 &= sizeof(uint32_t) * CHAR_BIT - 1;
+	r2 &= TEST_SHIFT32_MASK;
 	r4 = (uint32_t)r4 << r2;
 
 	dve.out[4].u64 = r4;
-- 
2.34.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-11-30 16:50:10.003580557 +0100
+++ 0070-test-bpf-fix-undefined-behavior-with-clang.patch	2021-11-30 16:50:05.746873207 +0100
@@ -1 +1 @@
-From 3ac2dffae88e8eb5c374b1fdd40d605014526510 Mon Sep 17 00:00:00 2001
+From 0f30d115c5cdec4b1dbdda29fedf07a77d3565fd Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 3ac2dffae88e8eb5c374b1fdd40d605014526510 ]
+
@@ -26 +27,0 @@
-Cc: stable at dpdk.org
@@ -36 +37 @@
-index 8118a1849b..7fcf92e716 100644
+index 88048b4644..533d8ba878 100644
@@ -39 +40 @@
-@@ -59,6 +59,9 @@ struct dummy_mbuf {
+@@ -51,6 +51,9 @@ struct dummy_net {
@@ -49 +50 @@
-@@ -548,15 +551,25 @@ static const struct ebpf_insn test_shift1_prog[] = {
+@@ -540,15 +543,25 @@ static const struct ebpf_insn test_shift1_prog[] = {
@@ -78 +79 @@
-@@ -590,7 +603,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
+@@ -582,7 +595,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
@@ -87 +88 @@
-@@ -600,7 +613,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
+@@ -592,7 +605,7 @@ static const struct ebpf_insn test_shift1_prog[] = {
@@ -96 +97 @@
-@@ -666,8 +679,10 @@ test_shift1_check(uint64_t rc, const void *arg)
+@@ -658,8 +671,10 @@ test_shift1_check(uint64_t rc, const void *arg)
@@ -108 +109 @@
-@@ -676,9 +691,9 @@ test_shift1_check(uint64_t rc, const void *arg)
+@@ -668,9 +683,9 @@ test_shift1_check(uint64_t rc, const void *arg)