[PATCH v2 bpf-next 8/9] selftests/bpf: add realistic loop tests

[Alexei Starovoitov <ast@kernel.org>]

Add a bunch of loop tests. Most of them are created by replacing
'#pragma unroll' with '#pragma clang loop unroll(disable)'

Several tests are artificially large:
  /* partial unroll. llvm will unroll loop ~150 times.
   * C loop count -> 600.
   * Asm loop count -> 4.
   * 16k insns in loop body.
   * Total of 5 such loops. Total program size ~82k insns.
   */
  "./pyperf600.o",

  /* no unroll at all.
   * C loop count -> 600.
   * ASM loop count -> 600.
   * ~110 insns in loop body.
   * Total of 5 such loops. Total program size ~1500 insns.
   */
  "./pyperf600_nounroll.o",

  /* partial unroll. 19k insn in a loop.
   * Total program size 20.8k insn.
   * ~350k processed_insns
   */
  "./strobemeta.o",

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
---
 .../bpf/prog_tests/bpf_verif_scale.c          |  67 ++-
 tools/testing/selftests/bpf/progs/loop1.c     |  28 +
 tools/testing/selftests/bpf/progs/loop2.c     |  28 +
 tools/testing/selftests/bpf/progs/loop3.c     |  22 +
 tools/testing/selftests/bpf/progs/pyperf.h    |   6 +-
 tools/testing/selftests/bpf/progs/pyperf600.c |   9 +
 .../selftests/bpf/progs/pyperf600_nounroll.c  |   8 +
 .../testing/selftests/bpf/progs/strobemeta.c  |  10 +
 .../testing/selftests/bpf/progs/strobemeta.h  | 528 ++++++++++++++++++
 .../bpf/progs/strobemeta_nounroll1.c          |   9 +
 .../bpf/progs/strobemeta_nounroll2.c          |   9 +
 .../selftests/bpf/progs/test_seg6_loop.c      | 261 +++++++++
 .../selftests/bpf/progs/test_sysctl_loop1.c   |  71 +++
 .../selftests/bpf/progs/test_sysctl_loop2.c   |  72 +++
 .../selftests/bpf/progs/test_xdp_loop.c       | 231 ++++++++
 15 files changed, 1347 insertions(+), 12 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/loop1.c
 create mode 100644 tools/testing/selftests/bpf/progs/loop2.c
 create mode 100644 tools/testing/selftests/bpf/progs/loop3.c
 create mode 100644 tools/testing/selftests/bpf/progs/pyperf600.c
 create mode 100644 tools/testing/selftests/bpf/progs/pyperf600_nounroll.c
 create mode 100644 tools/testing/selftests/bpf/progs/strobemeta.c
 create mode 100644 tools/testing/selftests/bpf/progs/strobemeta.h
 create mode 100644 tools/testing/selftests/bpf/progs/strobemeta_nounroll1.c
 create mode 100644 tools/testing/selftests/bpf/progs/strobemeta_nounroll2.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_seg6_loop.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sysctl_loop1.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_sysctl_loop2.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_loop.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
index c0091137074b..e1b55261526f 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
@@ -5,7 +5,7 @@ static int libbpf_debug_print(enum libbpf_print_level level,
 			      const char *format, va_list args)
 {
 	if (level != LIBBPF_DEBUG)
-		return 0;
+		return vfprintf(stderr, format, args);
 
 	if (!strstr(format, "verifier log"))
 		return 0;
@@ -32,24 +32,69 @@ static int check_load(const char *file, enum bpf_prog_type type)
 
 void test_bpf_verif_scale(void)
 {
-	const char *scale[] = {
-		"./test_verif_scale1.o", "./test_verif_scale2.o", "./test_verif_scale3.o"
+	const char *sched_cls[] = {
+		"./test_verif_scale1.o", "./test_verif_scale2.o", "./test_verif_scale3.o",
 	};
-	const char *pyperf[] = {
-		"./pyperf50.o",	"./pyperf100.o", "./pyperf180.o"
+	const char *raw_tp[] = {
+		/* full unroll by llvm */
+		"./pyperf50.o",	"./pyperf100.o", "./pyperf180.o",
+
+		/* partial unroll. llvm will unroll loop ~150 times.
+		 * C loop count -> 600.
+		 * Asm loop count -> 4.
+		 * 16k insns in loop body.
+		 * Total of 5 such loops. Total program size ~82k insns.
+		 */
+		"./pyperf600.o",
+
+		/* no unroll at all.
+		 * C loop count -> 600.
+		 * ASM loop count -> 600.
+		 * ~110 insns in loop body.
+		 * Total of 5 such loops. Total program size ~1500 insns.
+		 */
+		"./pyperf600_nounroll.o",
+
+		"./loop1.o", "./loop2.o",
+
+		/* partial unroll. 19k insn in a loop.
+		 * Total program size 20.8k insn.
+		 * ~350k processed_insns
+		 */
+		"./strobemeta.o",
+
+		/* no unroll, tiny loops */
+		"./strobemeta_nounroll1.o",
+		"./strobemeta_nounroll2.o",
+	};
+	const char *cg_sysctl[] = {
+		"./test_sysctl_loop1.o", "./test_sysctl_loop2.o",
 	};
 	int err, i;
 
 	if (verifier_stats)
 		libbpf_set_print(libbpf_debug_print);
 
-	for (i = 0; i < ARRAY_SIZE(scale); i++) {
-		err = check_load(scale[i], BPF_PROG_TYPE_SCHED_CLS);
-		printf("test_scale:%s:%s\n", scale[i], err ? "FAIL" : "OK");
+	err = check_load("./loop3.o", BPF_PROG_TYPE_RAW_TRACEPOINT);
+	printf("test_scale:loop3:%s\n", err ? (error_cnt--, "OK") : "FAIL");
+
+	for (i = 0; i < ARRAY_SIZE(sched_cls); i++) {
+		err = check_load(sched_cls[i], BPF_PROG_TYPE_SCHED_CLS);
+		printf("test_scale:%s:%s\n", sched_cls[i], err ? "FAIL" : "OK");
 	}
 
-	for (i = 0; i < ARRAY_SIZE(pyperf); i++) {
-		err = check_load(pyperf[i], BPF_PROG_TYPE_RAW_TRACEPOINT);
-		printf("test_scale:%s:%s\n", pyperf[i], err ? "FAIL" : "OK");
+	for (i = 0; i < ARRAY_SIZE(raw_tp); i++) {
+		err = check_load(raw_tp[i], BPF_PROG_TYPE_RAW_TRACEPOINT);
+		printf("test_scale:%s:%s\n", raw_tp[i], err ? "FAIL" : "OK");
 	}
+
+	for (i = 0; i < ARRAY_SIZE(cg_sysctl); i++) {
+		err = check_load(cg_sysctl[i], BPF_PROG_TYPE_CGROUP_SYSCTL);
+		printf("test_scale:%s:%s\n", cg_sysctl[i], err ? "FAIL" : "OK");
+	}
+	err = check_load("./test_xdp_loop.o", BPF_PROG_TYPE_XDP);
+	printf("test_scale:test_xdp_loop:%s\n", err ? "FAIL" : "OK");
+
+	err = check_load("./test_seg6_loop.o", BPF_PROG_TYPE_LWT_SEG6LOCAL);
+	printf("test_scale:test_seg6_loop:%s\n", err ? "FAIL" : "OK");
 }
diff --git a/tools/testing/selftests/bpf/progs/loop1.c b/tools/testing/selftests/bpf/progs/loop1.c
new file mode 100644
index 000000000000..dea395af9ea9
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop1.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("raw_tracepoint/kfree_skb")
+int nested_loops(volatile struct pt_regs* ctx)
+{
+	int i, j, sum = 0, m;
+
+	for (j = 0; j < 300; j++)
+		for (i = 0; i < j; i++) {
+			if (j & 1)
+				m = ctx->rax;
+			else
+				m = j;
+			sum += i * m;
+		}
+
+	return sum;
+}
diff --git a/tools/testing/selftests/bpf/progs/loop2.c b/tools/testing/selftests/bpf/progs/loop2.c
new file mode 100644
index 000000000000..0637bd8e8bcf
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop2.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("raw_tracepoint/consume_skb")
+int while_true(volatile struct pt_regs* ctx)
+{
+	int i = 0;
+
+	while (true) {
+		if (ctx->rax & 1)
+			i += 3;
+		else
+			i += 7;
+		if (i > 40)
+			break;
+	}
+
+	return i;
+}
diff --git a/tools/testing/selftests/bpf/progs/loop3.c b/tools/testing/selftests/bpf/progs/loop3.c
new file mode 100644
index 000000000000..30a0f6cba080
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop3.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("raw_tracepoint/consume_skb")
+int while_true(volatile struct pt_regs* ctx)
+{
+	__u64 i = 0, sum = 0;
+	do {
+		i++;
+		sum += ctx->rax;
+	} while (i < 0x100000000ULL);
+	return sum;
+}
diff --git a/tools/testing/selftests/bpf/progs/pyperf.h b/tools/testing/selftests/bpf/progs/pyperf.h
index 0cc5e4ee90bd..6b0781391be5 100644
--- a/tools/testing/selftests/bpf/progs/pyperf.h
+++ b/tools/testing/selftests/bpf/progs/pyperf.h
@@ -220,7 +220,11 @@ static inline __attribute__((__always_inline__)) int __on_event(struct pt_regs *
 		int32_t* symbol_counter = bpf_map_lookup_elem(&symbolmap, &sym);
 		if (symbol_counter == NULL)
 			return 0;
-#pragma unroll
+#ifdef NO_UNROLL
+#pragma clang loop unroll(disable)
+#else
+#pragma clang loop unroll(full)
+#endif
 		/* Unwind python stack */
 		for (int i = 0; i < STACK_MAX_LEN; ++i) {
 			if (frame_ptr && get_frame_data(frame_ptr, pidData, &frame, &sym)) {
diff --git a/tools/testing/selftests/bpf/progs/pyperf600.c b/tools/testing/selftests/bpf/progs/pyperf600.c
new file mode 100644
index 000000000000..cb49b89e37cd
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/pyperf600.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#define STACK_MAX_LEN 600
+/* clang will not unroll the loop 600 times.
+ * Instead it will unroll it to the amount it deemed
+ * appropriate, but the loop will still execute 600 times.
+ * Total program size is around 90k insns
+ */
+#include "pyperf.h"
diff --git a/tools/testing/selftests/bpf/progs/pyperf600_nounroll.c b/tools/testing/selftests/bpf/progs/pyperf600_nounroll.c
new file mode 100644
index 000000000000..6beff7502f4d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/pyperf600_nounroll.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#define STACK_MAX_LEN 600
+#define NO_UNROLL
+/* clang will not unroll at all.
+ * Total program size is around 2k insns
+ */
+#include "pyperf.h"
diff --git a/tools/testing/selftests/bpf/progs/strobemeta.c b/tools/testing/selftests/bpf/progs/strobemeta.c
new file mode 100644
index 000000000000..d3df3d86f092
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/strobemeta.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+// Copyright (c) 2019 Facebook
+
+#define STROBE_MAX_INTS 2
+#define STROBE_MAX_STRS 25
+#define STROBE_MAX_MAPS 100
+#define STROBE_MAX_MAP_ENTRIES 20
+/* full unroll by llvm #undef NO_UNROLL */
+#include "strobemeta.h"
+
diff --git a/tools/testing/selftests/bpf/progs/strobemeta.h b/tools/testing/selftests/bpf/progs/strobemeta.h
new file mode 100644
index 000000000000..1ff73f60a3e4
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/strobemeta.h
@@ -0,0 +1,528 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include <linux/ptrace.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include "bpf_helpers.h"
+
+typedef uint32_t pid_t;
+struct task_struct {};
+
+#define TASK_COMM_LEN 16
+#define PERF_MAX_STACK_DEPTH 127
+
+#define STROBE_TYPE_INVALID 0
+#define STROBE_TYPE_INT 1
+#define STROBE_TYPE_STR 2
+#define STROBE_TYPE_MAP 3
+
+#define STACK_TABLE_EPOCH_SHIFT 20
+#define STROBE_MAX_STR_LEN 1
+#define STROBE_MAX_CFGS 32
+#define STROBE_MAX_PAYLOAD						\
+	(STROBE_MAX_STRS * STROBE_MAX_STR_LEN +				\
+	STROBE_MAX_MAPS * (1 + STROBE_MAX_MAP_ENTRIES * 2) * STROBE_MAX_STR_LEN)
+
+struct strobe_value_header {
+	/*
+	 * meaning depends on type:
+	 * 1. int: 0, if value not set, 1 otherwise
+	 * 2. str: 1 always, whether value is set or not is determined by ptr
+	 * 3. map: 1 always, pointer points to additional struct with number
+	 *    of entries (up to STROBE_MAX_MAP_ENTRIES)
+	 */
+	uint16_t len;
+	/*
+	 * _reserved might be used for some future fields/flags, but we always
+	 * want to keep strobe_value_header to be 8 bytes, so BPF can read 16
+	 * bytes in one go and get both header and value
+	 */
+	uint8_t _reserved[6];
+};
+
+/*
+ * strobe_value_generic is used from BPF probe only, but needs to be a union
+ * of strobe_value_int/strobe_value_str/strobe_value_map
+ */
+struct strobe_value_generic {
+	struct strobe_value_header header;
+	union {
+		int64_t val;
+		void *ptr;
+	};
+};
+
+struct strobe_value_int {
+	struct strobe_value_header header;
+	int64_t value;
+};
+
+struct strobe_value_str {
+	struct strobe_value_header header;
+	const char* value;
+};
+
+struct strobe_value_map {
+	struct strobe_value_header header;
+	const struct strobe_map_raw* value;
+};
+
+struct strobe_map_entry {
+	const char* key;
+	const char* val;
+};
+
+/*
+ * Map of C-string key/value pairs with fixed maximum capacity. Each map has
+ * corresponding int64 ID, which application can use (or ignore) in whatever
+ * way appropriate. Map is "write-only", there is no way to get data out of
+ * map. Map is intended to be used to provide metadata for profilers and is
+ * not to be used for internal in-app communication. All methods are
+ * thread-safe.
+ */
+struct strobe_map_raw {
+	/*
+	 * general purpose unique ID that's up to application to decide
+	 * whether and how to use; for request metadata use case id is unique
+	 * request ID that's used to match metadata with stack traces on
+	 * Strobelight backend side
+	 */
+	int64_t id;
+	/* number of used entries in map */
+	int64_t cnt;
+	/*
+	 * having volatile doesn't change anything on BPF side, but clang
+	 * emits warnings for passing `volatile const char *` into
+	 * bpf_probe_read_str that expects just `const char *`
+	 */
+	const char* tag;
+	/*
+	 * key/value entries, each consisting of 2 pointers to key and value
+	 * C strings
+	 */
+	struct strobe_map_entry entries[STROBE_MAX_MAP_ENTRIES];
+};
+
+/* Following values define supported values of TLS mode */
+#define TLS_NOT_SET -1
+#define TLS_LOCAL_EXEC 0
+#define TLS_IMM_EXEC 1
+#define TLS_GENERAL_DYN 2
+
+/*
+ * structure that universally represents TLS location (both for static
+ * executables and shared libraries)
+ */
+struct strobe_value_loc {
+	/*
+	 * tls_mode defines what TLS mode was used for particular metavariable:
+	 * - -1 (TLS_NOT_SET) - no metavariable;
+	 * - 0 (TLS_LOCAL_EXEC) - Local Executable mode;
+	 * - 1 (TLS_IMM_EXEC) - Immediate Executable mode;
+	 * - 2 (TLS_GENERAL_DYN) - General Dynamic mode;
+	 * Local Dynamic mode is not yet supported, because never seen in
+	 * practice.  Mode defines how offset field is interpreted. See
+	 * calc_location() in below for details.
+	 */
+	int64_t tls_mode;
+	/*
+	 * TLS_LOCAL_EXEC: offset from thread pointer (fs:0 for x86-64,
+	 * tpidr_el0 for aarch64).
+	 * TLS_IMM_EXEC: absolute address of GOT entry containing offset
+	 * from thread pointer;
+	 * TLS_GENERAL_DYN: absolute addres of double GOT entry
+	 * containing tls_index_t struct;
+	 */
+	int64_t offset;
+};
+
+struct strobemeta_cfg {
+	int64_t req_meta_idx;
+	struct strobe_value_loc int_locs[STROBE_MAX_INTS];
+	struct strobe_value_loc str_locs[STROBE_MAX_STRS];
+	struct strobe_value_loc map_locs[STROBE_MAX_MAPS];
+};
+
+struct strobe_map_descr {
+	uint64_t id;
+	int16_t tag_len;
+	/*
+	 * cnt <0 - map value isn't set;
+	 * 0 - map has id set, but no key/value entries
+	 */
+	int16_t cnt;
+	/*
+	 * both key_lens[i] and val_lens[i] should be >0 for present key/value
+	 * entry
+	 */
+	uint16_t key_lens[STROBE_MAX_MAP_ENTRIES];
+	uint16_t val_lens[STROBE_MAX_MAP_ENTRIES];
+};
+
+struct strobemeta_payload {
+	/* req_id has valid request ID, if req_meta_valid == 1 */
+	int64_t req_id;
+	uint8_t req_meta_valid;
+	/*
+	 * mask has Nth bit set to 1, if Nth metavar was present and
+	 * successfully read
+	 */
+	uint64_t int_vals_set_mask;
+	int64_t int_vals[STROBE_MAX_INTS];
+	/* len is >0 for present values */
+	uint16_t str_lens[STROBE_MAX_STRS];
+	/* if map_descrs[i].cnt == -1, metavar is not present/set */
+	struct strobe_map_descr map_descrs[STROBE_MAX_MAPS];
+	/*
+	 * payload has compactly packed values of str and map variables in the
+	 * form: strval1\0strval2\0map1key1\0map1val1\0map2key1\0map2val1\0
+	 * (and so on); str_lens[i], key_lens[i] and val_lens[i] determines
+	 * value length
+	 */
+	char payload[STROBE_MAX_PAYLOAD];
+};
+
+struct strobelight_bpf_sample {
+	uint64_t ktime;
+	char comm[TASK_COMM_LEN];
+	pid_t pid;
+	int user_stack_id;
+	int kernel_stack_id;
+	int has_meta;
+	struct strobemeta_payload metadata;
+	/*
+	 * makes it possible to pass (<real payload size> + 1) as data size to
+	 * perf_submit() to avoid perf_submit's paranoia about passing zero as
+	 * size, as it deduces that <real payload size> might be
+	 * **theoretically** zero
+	 */
+	char dummy_safeguard;
+};
+
+struct bpf_map_def SEC("maps") samples = {
+	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = 32,
+};
+
+struct bpf_map_def SEC("maps") stacks_0 = {
+	.type = BPF_MAP_TYPE_STACK_TRACE,
+	.key_size = sizeof(uint32_t),
+	.value_size = sizeof(uint64_t) * PERF_MAX_STACK_DEPTH,
+	.max_entries = 16,
+};
+
+struct bpf_map_def SEC("maps") stacks_1 = {
+	.type = BPF_MAP_TYPE_STACK_TRACE,
+	.key_size = sizeof(uint32_t),
+	.value_size = sizeof(uint64_t) * PERF_MAX_STACK_DEPTH,
+	.max_entries = 16,
+};
+
+struct bpf_map_def SEC("maps") sample_heap = {
+	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size = sizeof(uint32_t),
+	.value_size = sizeof(struct strobelight_bpf_sample),
+	.max_entries = 1,
+};
+
+struct bpf_map_def SEC("maps") strobemeta_cfgs = {
+	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size = sizeof(pid_t),
+	.value_size = sizeof(struct strobemeta_cfg),
+	.max_entries = STROBE_MAX_CFGS,
+};
+
+/* Type for the dtv.  */
+/* https://github.com/lattera/glibc/blob/master/nptl/sysdeps/x86_64/tls.h#L34 */
+typedef union dtv {
+	size_t counter;
+	struct {
+		void* val;
+		bool is_static;
+	} pointer;
+} dtv_t;
+
+/* Partial definition for tcbhead_t */
+/* https://github.com/bminor/glibc/blob/master/sysdeps/x86_64/nptl/tls.h#L42 */
+struct tcbhead {
+	void* tcb;
+	dtv_t* dtv;
+};
+
+/*
+ * TLS module/offset information for shared library case.
+ * For x86-64, this is mapped onto two entries in GOT.
+ * For aarch64, this is pointed to by second GOT entry.
+ */
+struct tls_index {
+	uint64_t module;
+	uint64_t offset;
+};
+
+static inline __attribute__((always_inline))
+void *calc_location(struct strobe_value_loc *loc, void *tls_base)
+{
+	/*
+	 * tls_mode value is:
+	 * - -1 (TLS_NOT_SET), if no metavar is present;
+	 * - 0 (TLS_LOCAL_EXEC), if metavar uses Local Executable mode of TLS
+	 * (offset from fs:0 for x86-64 or tpidr_el0 for aarch64);
+	 * - 1 (TLS_IMM_EXEC), if metavar uses Immediate Executable mode of TLS;
+	 * - 2 (TLS_GENERAL_DYN), if metavar uses General Dynamic mode of TLS;
+	 * This schema allows to use something like:
+	 * (tls_mode + 1) * (tls_base + offset)
+	 * to get NULL for "no metavar" location, or correct pointer for local
+	 * executable mode without doing extra ifs.
+	 */
+	if (loc->tls_mode <= TLS_LOCAL_EXEC) {
+		/* static executable is simple, we just have offset from
+		 * tls_base */
+		void *addr = tls_base + loc->offset;
+		/* multiply by (tls_mode + 1) to get NULL, if we have no
+		 * metavar in this slot */
+		return (void *)((loc->tls_mode + 1) * (int64_t)addr);
+	}
+	/*
+	 * Other modes are more complicated, we need to jump through few hoops.
+	 *
+	 * For immediate executable mode (currently supported only for aarch64):
+	 *  - loc->offset is pointing to a GOT entry containing fixed offset
+	 *  relative to tls_base;
+	 *
+	 * For general dynamic mode:
+	 *  - loc->offset is pointing to a beginning of double GOT entries;
+	 *  - (for aarch64 only) second entry points to tls_index_t struct;
+	 *  - (for x86-64 only) two GOT entries are already tls_index_t;
+	 *  - tls_index_t->module is used to find start of TLS section in
+	 *  which variable resides;
+	 *  - tls_index_t->offset provides offset within that TLS section,
+	 *  pointing to value of variable.
+	 */
+	struct tls_index tls_index;
+	dtv_t *dtv;
+	void *tls_ptr;
+
+	bpf_probe_read(&tls_index, sizeof(struct tls_index),
+		       (void *)loc->offset);
+	/* valid module index is always positive */
+	if (tls_index.module > 0) {
+		/* dtv = ((struct tcbhead *)tls_base)->dtv[tls_index.module] */
+		bpf_probe_read(&dtv, sizeof(dtv),
+			       &((struct tcbhead *)tls_base)->dtv);
+		dtv += tls_index.module;
+	} else {
+		dtv = NULL;
+	}
+	bpf_probe_read(&tls_ptr, sizeof(void *), dtv);
+	/* if pointer has (void *)-1 value, then TLS wasn't initialized yet */
+	return tls_ptr && tls_ptr != (void *)-1
+		? tls_ptr + tls_index.offset
+		: NULL;
+}
+
+static inline __attribute__((always_inline))
+void read_int_var(struct strobemeta_cfg *cfg, size_t idx, void *tls_base,
+		  struct strobe_value_generic *value,
+		  struct strobemeta_payload *data)
+{
+	void *location = calc_location(&cfg->int_locs[idx], tls_base);
+	if (!location)
+		return;
+
+	bpf_probe_read(value, sizeof(struct strobe_value_generic), location);
+	data->int_vals[idx] = value->val;
+	if (value->header.len)
+		data->int_vals_set_mask |= (1 << idx);
+}
+
+static inline __attribute__((always_inline))
+uint64_t read_str_var(struct strobemeta_cfg* cfg, size_t idx, void *tls_base,
+		      struct strobe_value_generic *value,
+		      struct strobemeta_payload *data, void *payload)
+{
+	void *location;
+	uint32_t len;
+
+	data->str_lens[idx] = 0;
+	location = calc_location(&cfg->str_locs[idx], tls_base);
+	if (!location)
+		return 0;
+
+	bpf_probe_read(value, sizeof(struct strobe_value_generic), location);
+	len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN, value->ptr);
+	/*
+	 * if bpf_probe_read_str returns error (<0), due to casting to
+	 * unsinged int, it will become big number, so next check is
+	 * sufficient to check for errors AND prove to BPF verifier, that
+	 * bpf_probe_read_str won't return anything bigger than
+	 * STROBE_MAX_STR_LEN
+	 */
+	if (len > STROBE_MAX_STR_LEN)
+		return 0;
+
+	data->str_lens[idx] = len;
+	return len;
+}
+
+static inline __attribute__((always_inline))
+void *read_map_var(struct strobemeta_cfg *cfg, size_t idx, void *tls_base,
+		   struct strobe_value_generic *value,
+		   struct strobemeta_payload* data, void *payload)
+{
+	struct strobe_map_descr* descr = &data->map_descrs[idx];
+	struct strobe_map_raw map;
+	void *location;
+	uint32_t len;
+	int i;
+
+	descr->tag_len = 0; /* presume no tag is set */
+	descr->cnt = -1; /* presume no value is set */
+
+	location = calc_location(&cfg->map_locs[idx], tls_base);
+	if (!location)
+		return payload;
+
+	bpf_probe_read(value, sizeof(struct strobe_value_generic), location);
+	if (bpf_probe_read(&map, sizeof(struct strobe_map_raw), value->ptr))
+		return payload;
+
+	descr->id = map.id;
+	descr->cnt = map.cnt;
+	if (cfg->req_meta_idx == idx) {
+		data->req_id = map.id;
+		data->req_meta_valid = 1;
+	}
+
+	len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN, map.tag);
+	if (len <= STROBE_MAX_STR_LEN) {
+		descr->tag_len = len;
+		payload += len;
+	}
+
+#ifdef NO_UNROLL
+#pragma clang loop unroll(disable)
+#else
+#pragma unroll
+#endif
+	for (int i = 0; i < STROBE_MAX_MAP_ENTRIES && i < map.cnt; ++i) {
+		descr->key_lens[i] = 0;
+		len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN,
+					 map.entries[i].key);
+		if (len <= STROBE_MAX_STR_LEN) {
+			descr->key_lens[i] = len;
+			payload += len;
+		}
+		descr->val_lens[i] = 0;
+		len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN,
+					 map.entries[i].val);
+		if (len <= STROBE_MAX_STR_LEN) {
+			descr->val_lens[i] = len;
+			payload += len;
+		}
+	}
+
+	return payload;
+}
+
+/*
+ * read_strobe_meta returns NULL, if no metadata was read; otherwise returns
+ * pointer to *right after* payload ends
+ */
+static inline __attribute__((always_inline))
+void *read_strobe_meta(struct task_struct* task,
+		       struct strobemeta_payload* data) {
+	pid_t pid = bpf_get_current_pid_tgid() >> 32;
+	struct strobe_value_generic value = {0};
+	struct strobemeta_cfg *cfg;
+	void *tls_base, *payload;
+
+	cfg = bpf_map_lookup_elem(&strobemeta_cfgs, &pid);
+	if (!cfg)
+		return NULL;
+
+	data->int_vals_set_mask = 0;
+	data->req_meta_valid = 0;
+	payload = data->payload;
+	/*
+	 * we don't have struct task_struct definition, it should be:
+	 * tls_base = (void *)task->thread.fsbase;
+	 */
+	tls_base = (void *)task;
+
+#ifdef NO_UNROLL
+#pragma clang loop unroll(disable)
+#else
+#pragma unroll
+#endif
+	for (int i = 0; i < STROBE_MAX_INTS; ++i) {
+		read_int_var(cfg, i, tls_base, &value, data);
+	}
+#ifdef NO_UNROLL
+#pragma clang loop unroll(disable)
+#else
+#pragma unroll
+#endif
+	for (int i = 0; i < STROBE_MAX_STRS; ++i) {
+		payload += read_str_var(cfg, i, tls_base, &value, data, payload);
+	}
+#ifdef NO_UNROLL
+#pragma clang loop unroll(disable)
+#else
+#pragma unroll
+#endif
+	for (int i = 0; i < STROBE_MAX_MAPS; ++i) {
+		payload = read_map_var(cfg, i, tls_base, &value, data, payload);
+	}
+	/*
+	 * return pointer right after end of payload, so it's possible to
+	 * calculate exact amount of useful data that needs to be sent
+	 */
+	return payload;
+}
+
+SEC("raw_tracepoint/kfree_skb")
+int on_event(struct pt_regs *ctx) {
+	pid_t pid =  bpf_get_current_pid_tgid() >> 32;
+	struct strobelight_bpf_sample* sample;
+	struct task_struct *task;
+	uint32_t zero = 0;
+	uint64_t ktime_ns;
+	void *sample_end;
+
+	sample = bpf_map_lookup_elem(&sample_heap, &zero);
+	if (!sample)
+		return 0; /* this will never happen */
+
+	sample->pid = pid;
+	bpf_get_current_comm(&sample->comm, TASK_COMM_LEN);
+	ktime_ns = bpf_ktime_get_ns();
+	sample->ktime = ktime_ns;
+
+	task = (struct task_struct *)bpf_get_current_task();
+	sample_end = read_strobe_meta(task, &sample->metadata);
+	sample->has_meta = sample_end != NULL;
+	sample_end = sample_end ? : &sample->metadata;
+
+	if ((ktime_ns >> STACK_TABLE_EPOCH_SHIFT) & 1) {
+		sample->kernel_stack_id = bpf_get_stackid(ctx, &stacks_1, 0);
+		sample->user_stack_id = bpf_get_stackid(ctx, &stacks_1, BPF_F_USER_STACK);
+	} else {
+		sample->kernel_stack_id = bpf_get_stackid(ctx, &stacks_0, 0);
+		sample->user_stack_id = bpf_get_stackid(ctx, &stacks_0, BPF_F_USER_STACK);
+	}
+
+	uint64_t sample_size = sample_end - (void *)sample;
+	/* should always be true */
+	if (sample_size < sizeof(struct strobelight_bpf_sample))
+		bpf_perf_event_output(ctx, &samples, 0, sample, 1 + sample_size);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/strobemeta_nounroll1.c b/tools/testing/selftests/bpf/progs/strobemeta_nounroll1.c
new file mode 100644
index 000000000000..f0a1669e11d6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/strobemeta_nounroll1.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+// Copyright (c) 2019 Facebook
+
+#define STROBE_MAX_INTS 2
+#define STROBE_MAX_STRS 25
+#define STROBE_MAX_MAPS 13
+#define STROBE_MAX_MAP_ENTRIES 20
+#define NO_UNROLL
+#include "strobemeta.h"
diff --git a/tools/testing/selftests/bpf/progs/strobemeta_nounroll2.c b/tools/testing/selftests/bpf/progs/strobemeta_nounroll2.c
new file mode 100644
index 000000000000..4291a7d642e7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/strobemeta_nounroll2.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+// Copyright (c) 2019 Facebook
+
+#define STROBE_MAX_INTS 2
+#define STROBE_MAX_STRS 25
+#define STROBE_MAX_MAPS 30
+#define STROBE_MAX_MAP_ENTRIES 20
+#define NO_UNROLL
+#include "strobemeta.h"
diff --git a/tools/testing/selftests/bpf/progs/test_seg6_loop.c b/tools/testing/selftests/bpf/progs/test_seg6_loop.c
new file mode 100644
index 000000000000..463964d79f73
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_seg6_loop.c
@@ -0,0 +1,261 @@
+#include <stddef.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <linux/seg6_local.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+/* Packet parsing state machine helpers. */
+#define cursor_advance(_cursor, _len) \
+	({ void *_tmp = _cursor; _cursor += _len; _tmp; })
+
+#define SR6_FLAG_ALERT (1 << 4)
+
+#define htonll(x) ((bpf_htonl(1)) == 1 ? (x) : ((uint64_t)bpf_htonl((x) & \
+				0xFFFFFFFF) << 32) | bpf_htonl((x) >> 32))
+#define ntohll(x) ((bpf_ntohl(1)) == 1 ? (x) : ((uint64_t)bpf_ntohl((x) & \
+				0xFFFFFFFF) << 32) | bpf_ntohl((x) >> 32))
+#define BPF_PACKET_HEADER __attribute__((packed))
+
+struct ip6_t {
+	unsigned int ver:4;
+	unsigned int priority:8;
+	unsigned int flow_label:20;
+	unsigned short payload_len;
+	unsigned char next_header;
+	unsigned char hop_limit;
+	unsigned long long src_hi;
+	unsigned long long src_lo;
+	unsigned long long dst_hi;
+	unsigned long long dst_lo;
+} BPF_PACKET_HEADER;
+
+struct ip6_addr_t {
+	unsigned long long hi;
+	unsigned long long lo;
+} BPF_PACKET_HEADER;
+
+struct ip6_srh_t {
+	unsigned char nexthdr;
+	unsigned char hdrlen;
+	unsigned char type;
+	unsigned char segments_left;
+	unsigned char first_segment;
+	unsigned char flags;
+	unsigned short tag;
+
+	struct ip6_addr_t segments[0];
+} BPF_PACKET_HEADER;
+
+struct sr6_tlv_t {
+	unsigned char type;
+	unsigned char len;
+	unsigned char value[0];
+} BPF_PACKET_HEADER;
+
+static __attribute__((always_inline)) struct ip6_srh_t *get_srh(struct __sk_buff *skb)
+{
+	void *cursor, *data_end;
+	struct ip6_srh_t *srh;
+	struct ip6_t *ip;
+	uint8_t *ipver;
+
+	data_end = (void *)(long)skb->data_end;
+	cursor = (void *)(long)skb->data;
+	ipver = (uint8_t *)cursor;
+
+	if ((void *)ipver + sizeof(*ipver) > data_end)
+		return NULL;
+
+	if ((*ipver >> 4) != 6)
+		return NULL;
+
+	ip = cursor_advance(cursor, sizeof(*ip));
+	if ((void *)ip + sizeof(*ip) > data_end)
+		return NULL;
+
+	if (ip->next_header != 43)
+		return NULL;
+
+	srh = cursor_advance(cursor, sizeof(*srh));
+	if ((void *)srh + sizeof(*srh) > data_end)
+		return NULL;
+
+	if (srh->type != 4)
+		return NULL;
+
+	return srh;
+}
+
+static __attribute__((always_inline))
+int update_tlv_pad(struct __sk_buff *skb, uint32_t new_pad,
+		   uint32_t old_pad, uint32_t pad_off)
+{
+	int err;
+
+	if (new_pad != old_pad) {
+		err = bpf_lwt_seg6_adjust_srh(skb, pad_off,
+					  (int) new_pad - (int) old_pad);
+		if (err)
+			return err;
+	}
+
+	if (new_pad > 0) {
+		char pad_tlv_buf[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+					0, 0, 0};
+		struct sr6_tlv_t *pad_tlv = (struct sr6_tlv_t *) pad_tlv_buf;
+
+		pad_tlv->type = SR6_TLV_PADDING;
+		pad_tlv->len = new_pad - 2;
+
+		err = bpf_lwt_seg6_store_bytes(skb, pad_off,
+					       (void *)pad_tlv_buf, new_pad);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static __attribute__((always_inline))
+int is_valid_tlv_boundary(struct __sk_buff *skb, struct ip6_srh_t *srh,
+			  uint32_t *tlv_off, uint32_t *pad_size,
+			  uint32_t *pad_off)
+{
+	uint32_t srh_off, cur_off;
+	int offset_valid = 0;
+	int err;
+
+	srh_off = (char *)srh - (char *)(long)skb->data;
+	// cur_off = end of segments, start of possible TLVs
+	cur_off = srh_off + sizeof(*srh) +
+		sizeof(struct ip6_addr_t) * (srh->first_segment + 1);
+
+	*pad_off = 0;
+
+	// we can only go as far as ~10 TLVs due to the BPF max stack size
+	#pragma clang loop unroll(disable)
+	for (int i = 0; i < 100; i++) {
+		struct sr6_tlv_t tlv;
+
+		if (cur_off == *tlv_off)
+			offset_valid = 1;
+
+		if (cur_off >= srh_off + ((srh->hdrlen + 1) << 3))
+			break;
+
+		err = bpf_skb_load_bytes(skb, cur_off, &tlv, sizeof(tlv));
+		if (err)
+			return err;
+
+		if (tlv.type == SR6_TLV_PADDING) {
+			*pad_size = tlv.len + sizeof(tlv);
+			*pad_off = cur_off;
+
+			if (*tlv_off == srh_off) {
+				*tlv_off = cur_off;
+				offset_valid = 1;
+			}
+			break;
+
+		} else if (tlv.type == SR6_TLV_HMAC) {
+			break;
+		}
+
+		cur_off += sizeof(tlv) + tlv.len;
+	} // we reached the padding or HMAC TLVs, or the end of the SRH
+
+	if (*pad_off == 0)
+		*pad_off = cur_off;
+
+	if (*tlv_off == -1)
+		*tlv_off = cur_off;
+	else if (!offset_valid)
+		return -EINVAL;
+
+	return 0;
+}
+
+static __attribute__((always_inline))
+int add_tlv(struct __sk_buff *skb, struct ip6_srh_t *srh, uint32_t tlv_off,
+	    struct sr6_tlv_t *itlv, uint8_t tlv_size)
+{
+	uint32_t srh_off = (char *)srh - (char *)(long)skb->data;
+	uint8_t len_remaining, new_pad;
+	uint32_t pad_off = 0;
+	uint32_t pad_size = 0;
+	uint32_t partial_srh_len;
+	int err;
+
+	if (tlv_off != -1)
+		tlv_off += srh_off;
+
+	if (itlv->type == SR6_TLV_PADDING || itlv->type == SR6_TLV_HMAC)
+		return -EINVAL;
+
+	err = is_valid_tlv_boundary(skb, srh, &tlv_off, &pad_size, &pad_off);
+	if (err)
+		return err;
+
+	err = bpf_lwt_seg6_adjust_srh(skb, tlv_off, sizeof(*itlv) + itlv->len);
+	if (err)
+		return err;
+
+	err = bpf_lwt_seg6_store_bytes(skb, tlv_off, (void *)itlv, tlv_size);
+	if (err)
+		return err;
+
+	// the following can't be moved inside update_tlv_pad because the
+	// bpf verifier has some issues with it
+	pad_off += sizeof(*itlv) + itlv->len;
+	partial_srh_len = pad_off - srh_off;
+	len_remaining = partial_srh_len % 8;
+	new_pad = 8 - len_remaining;
+
+	if (new_pad == 1) // cannot pad for 1 byte only
+		new_pad = 9;
+	else if (new_pad == 8)
+		new_pad = 0;
+
+	return update_tlv_pad(skb, new_pad, pad_size, pad_off);
+}
+
+// Add an Egress TLV fc00::4, add the flag A,
+// and apply End.X action to fc42::1
+SEC("lwt_seg6local")
+int __add_egr_x(struct __sk_buff *skb)
+{
+	unsigned long long hi = 0xfc42000000000000;
+	unsigned long long lo = 0x1;
+	struct ip6_srh_t *srh = get_srh(skb);
+	uint8_t new_flags = SR6_FLAG_ALERT;
+	struct ip6_addr_t addr;
+	int err, offset;
+
+	if (srh == NULL)
+		return BPF_DROP;
+
+	uint8_t tlv[20] = {2, 18, 0, 0, 0xfd, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+			   0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4};
+
+	err = add_tlv(skb, srh, (srh->hdrlen+1) << 3,
+		      (struct sr6_tlv_t *)&tlv, 20);
+	if (err)
+		return BPF_DROP;
+
+	offset = sizeof(struct ip6_t) + offsetof(struct ip6_srh_t, flags);
+	err = bpf_lwt_seg6_store_bytes(skb, offset,
+				       (void *)&new_flags, sizeof(new_flags));
+	if (err)
+		return BPF_DROP;
+
+	addr.lo = htonll(lo);
+	addr.hi = htonll(hi);
+	err = bpf_lwt_seg6_action(skb, SEG6_LOCAL_ACTION_END_X,
+				  (void *)&addr, sizeof(addr));
+	if (err)
+		return BPF_DROP;
+	return BPF_REDIRECT;
+}
+char __license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_sysctl_loop1.c b/tools/testing/selftests/bpf/progs/test_sysctl_loop1.c
new file mode 100644
index 000000000000..608a06871572
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sysctl_loop1.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <stdint.h>
+#include <string.h>
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+
+#include "bpf_helpers.h"
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+/* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */
+#define TCP_MEM_LOOPS 28  /* because 30 doesn't fit into 512 bytes of stack */
+#define MAX_ULONG_STR_LEN 7
+#define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)
+
+static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
+{
+	volatile char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";
+	unsigned char i;
+	char name[64];
+	int ret;
+
+	memset(name, 0, sizeof(name));
+	ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
+	if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
+		return 0;
+
+#pragma clang loop unroll(disable)
+	for (i = 0; i < sizeof(tcp_mem_name); ++i)
+		if (name[i] != tcp_mem_name[i])
+			return 0;
+
+	return 1;
+}
+
+SEC("cgroup/sysctl")
+int sysctl_tcp_mem(struct bpf_sysctl *ctx)
+{
+	unsigned long tcp_mem[TCP_MEM_LOOPS] = {};
+	char value[MAX_VALUE_STR_LEN];
+	unsigned char i, off = 0;
+	int ret;
+
+	if (ctx->write)
+		return 0;
+
+	if (!is_tcp_mem(ctx))
+		return 0;
+
+	ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
+	if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
+		return 0;
+
+#pragma clang loop unroll(disable)
+	for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
+		ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
+				  tcp_mem + i);
+		if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
+			return 0;
+		off += ret & MAX_ULONG_STR_LEN;
+	}
+
+	return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_sysctl_loop2.c b/tools/testing/selftests/bpf/progs/test_sysctl_loop2.c
new file mode 100644
index 000000000000..cb201cbe11e7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sysctl_loop2.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <stdint.h>
+#include <string.h>
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+
+#include "bpf_helpers.h"
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+/* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */
+#define TCP_MEM_LOOPS 20  /* because 30 doesn't fit into 512 bytes of stack */
+#define MAX_ULONG_STR_LEN 7
+#define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)
+
+static __attribute__((noinline)) int is_tcp_mem(struct bpf_sysctl *ctx)
+{
+	volatile char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string_to_stress_byte_loop";
+	unsigned char i;
+	char name[64];
+	int ret;
+
+	memset(name, 0, sizeof(name));
+	ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
+	if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
+		return 0;
+
+#pragma clang loop unroll(disable)
+	for (i = 0; i < sizeof(tcp_mem_name); ++i)
+		if (name[i] != tcp_mem_name[i])
+			return 0;
+
+	return 1;
+}
+
+
+SEC("cgroup/sysctl")
+int sysctl_tcp_mem(struct bpf_sysctl *ctx)
+{
+	unsigned long tcp_mem[TCP_MEM_LOOPS] = {};
+	char value[MAX_VALUE_STR_LEN];
+	unsigned char i, off = 0;
+	int ret;
+
+	if (ctx->write)
+		return 0;
+
+	if (!is_tcp_mem(ctx))
+		return 0;
+
+	ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
+	if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
+		return 0;
+
+#pragma clang loop unroll(disable)
+	for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
+		ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
+				  tcp_mem + i);
+		if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
+			return 0;
+		off += ret & MAX_ULONG_STR_LEN;
+	}
+
+	return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_loop.c b/tools/testing/selftests/bpf/progs/test_xdp_loop.c
new file mode 100644
index 000000000000..7fa4677df22e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_loop.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <stddef.h>
+#include <string.h>
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/if_packet.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+#include <linux/tcp.h>
+#include <linux/pkt_cls.h>
+#include <sys/socket.h>
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+#include "test_iptunnel_common.h"
+
+int _version SEC("version") = 1;
+
+struct bpf_map_def SEC("maps") rxcnt = {
+	.type = BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u64),
+	.max_entries = 256,
+};
+
+struct bpf_map_def SEC("maps") vip2tnl = {
+	.type = BPF_MAP_TYPE_HASH,
+	.key_size = sizeof(struct vip),
+	.value_size = sizeof(struct iptnl_info),
+	.max_entries = MAX_IPTNL_ENTRIES,
+};
+
+static __always_inline void count_tx(__u32 protocol)
+{
+	__u64 *rxcnt_count;
+
+	rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
+	if (rxcnt_count)
+		*rxcnt_count += 1;
+}
+
+static __always_inline int get_dport(void *trans_data, void *data_end,
+				     __u8 protocol)
+{
+	struct tcphdr *th;
+	struct udphdr *uh;
+
+	switch (protocol) {
+	case IPPROTO_TCP:
+		th = (struct tcphdr *)trans_data;
+		if (th + 1 > data_end)
+			return -1;
+		return th->dest;
+	case IPPROTO_UDP:
+		uh = (struct udphdr *)trans_data;
+		if (uh + 1 > data_end)
+			return -1;
+		return uh->dest;
+	default:
+		return 0;
+	}
+}
+
+static __always_inline void set_ethhdr(struct ethhdr *new_eth,
+				       const struct ethhdr *old_eth,
+				       const struct iptnl_info *tnl,
+				       __be16 h_proto)
+{
+	memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
+	memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
+	new_eth->h_proto = h_proto;
+}
+
+static __always_inline int handle_ipv4(struct xdp_md *xdp)
+{
+	void *data_end = (void *)(long)xdp->data_end;
+	void *data = (void *)(long)xdp->data;
+	struct iptnl_info *tnl;
+	struct ethhdr *new_eth;
+	struct ethhdr *old_eth;
+	struct iphdr *iph = data + sizeof(struct ethhdr);
+	__u16 *next_iph;
+	__u16 payload_len;
+	struct vip vip = {};
+	int dport;
+	__u32 csum = 0;
+	int i;
+
+	if (iph + 1 > data_end)
+		return XDP_DROP;
+
+	dport = get_dport(iph + 1, data_end, iph->protocol);
+	if (dport == -1)
+		return XDP_DROP;
+
+	vip.protocol = iph->protocol;
+	vip.family = AF_INET;
+	vip.daddr.v4 = iph->daddr;
+	vip.dport = dport;
+	payload_len = bpf_ntohs(iph->tot_len);
+
+	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
+	/* It only does v4-in-v4 */
+	if (!tnl || tnl->family != AF_INET)
+		return XDP_PASS;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct iphdr)))
+		return XDP_DROP;
+
+	data = (void *)(long)xdp->data;
+	data_end = (void *)(long)xdp->data_end;
+
+	new_eth = data;
+	iph = data + sizeof(*new_eth);
+	old_eth = data + sizeof(*iph);
+
+	if (new_eth + 1 > data_end ||
+	    old_eth + 1 > data_end ||
+	    iph + 1 > data_end)
+		return XDP_DROP;
+
+	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IP));
+
+	iph->version = 4;
+	iph->ihl = sizeof(*iph) >> 2;
+	iph->frag_off =	0;
+	iph->protocol = IPPROTO_IPIP;
+	iph->check = 0;
+	iph->tos = 0;
+	iph->tot_len = bpf_htons(payload_len + sizeof(*iph));
+	iph->daddr = tnl->daddr.v4;
+	iph->saddr = tnl->saddr.v4;
+	iph->ttl = 8;
+
+	next_iph = (__u16 *)iph;
+#pragma clang loop unroll(disable)
+	for (i = 0; i < sizeof(*iph) >> 1; i++)
+		csum += *next_iph++;
+
+	iph->check = ~((csum & 0xffff) + (csum >> 16));
+
+	count_tx(vip.protocol);
+
+	return XDP_TX;
+}
+
+static __always_inline int handle_ipv6(struct xdp_md *xdp)
+{
+	void *data_end = (void *)(long)xdp->data_end;
+	void *data = (void *)(long)xdp->data;
+	struct iptnl_info *tnl;
+	struct ethhdr *new_eth;
+	struct ethhdr *old_eth;
+	struct ipv6hdr *ip6h = data + sizeof(struct ethhdr);
+	__u16 payload_len;
+	struct vip vip = {};
+	int dport;
+
+	if (ip6h + 1 > data_end)
+		return XDP_DROP;
+
+	dport = get_dport(ip6h + 1, data_end, ip6h->nexthdr);
+	if (dport == -1)
+		return XDP_DROP;
+
+	vip.protocol = ip6h->nexthdr;
+	vip.family = AF_INET6;
+	memcpy(vip.daddr.v6, ip6h->daddr.s6_addr32, sizeof(vip.daddr));
+	vip.dport = dport;
+	payload_len = ip6h->payload_len;
+
+	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
+	/* It only does v6-in-v6 */
+	if (!tnl || tnl->family != AF_INET6)
+		return XDP_PASS;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct ipv6hdr)))
+		return XDP_DROP;
+
+	data = (void *)(long)xdp->data;
+	data_end = (void *)(long)xdp->data_end;
+
+	new_eth = data;
+	ip6h = data + sizeof(*new_eth);
+	old_eth = data + sizeof(*ip6h);
+
+	if (new_eth + 1 > data_end || old_eth + 1 > data_end ||
+	    ip6h + 1 > data_end)
+		return XDP_DROP;
+
+	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IPV6));
+
+	ip6h->version = 6;
+	ip6h->priority = 0;
+	memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));
+	ip6h->payload_len = bpf_htons(bpf_ntohs(payload_len) + sizeof(*ip6h));
+	ip6h->nexthdr = IPPROTO_IPV6;
+	ip6h->hop_limit = 8;
+	memcpy(ip6h->saddr.s6_addr32, tnl->saddr.v6, sizeof(tnl->saddr.v6));
+	memcpy(ip6h->daddr.s6_addr32, tnl->daddr.v6, sizeof(tnl->daddr.v6));
+
+	count_tx(vip.protocol);
+
+	return XDP_TX;
+}
+
+SEC("xdp_tx_iptunnel")
+int _xdp_tx_iptunnel(struct xdp_md *xdp)
+{
+	void *data_end = (void *)(long)xdp->data_end;
+	void *data = (void *)(long)xdp->data;
+	struct ethhdr *eth = data;
+	__u16 h_proto;
+
+	if (eth + 1 > data_end)
+		return XDP_DROP;
+
+	h_proto = eth->h_proto;
+
+	if (h_proto == bpf_htons(ETH_P_IP))
+		return handle_ipv4(xdp);
+	else if (h_proto == bpf_htons(ETH_P_IPV6))
+
+		return handle_ipv6(xdp);
+	else
+		return XDP_DROP;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.20.0