selftests/bpf: Add BPF_CORE_READ and BPF_CORE_READ_STR_INTO macro tests

Validate BPF_CORE_READ correctness and handling of up to 9 levels of
nestedness using cyclic task->(group_leader->)*->tgid chains.

Also add a test of maximum-dpeth BPF_CORE_READ_STR_INTO() macro.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191008175942.1769476-8-andriin@fb.com

2 files changed, 62 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/progs/core_reloc_types.h b/tools/testing/selftests/bpf/progs/core_reloc_types.h
index f686a8138d90..9a6bdeb4894c 100644
--- a/tools/testing/selftests/bpf/progs/core_reloc_types.h
+++ b/tools/testing/selftests/bpf/progs/core_reloc_types.h
@@ -1,5 +1,14 @@
 #include <stdint.h>
 #include <stdbool.h>
+/*
+ * KERNEL
+ */
+
+struct core_reloc_kernel_output {
+	int valid[10];
+	char comm[16];
+	int comm_len;
+};
 
 /*
  * FLAVORS
diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
index 14ce688463de..50f609618b65 100644
--- a/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
@@ -13,9 +13,17 @@ static volatile struct data {
 	char out[256];
 } data;
 
+struct core_reloc_kernel_output {
+	int valid[10];
+	char comm[16];
+	int comm_len;
+};
+
 struct task_struct {
 	int pid;
 	int tgid;
+	char comm[16];
+	struct task_struct *group_leader;
 };
 
 #define CORE_READ(dst, src) bpf_core_read(dst, sizeof(*(dst)), src)
@@ -24,7 +32,9 @@ SEC("raw_tracepoint/sys_enter")
 int test_core_kernel(void *ctx)
 {
 	struct task_struct *task = (void *)bpf_get_current_task();
+	struct core_reloc_kernel_output *out = (void *)&data.out;
 	uint64_t pid_tgid = bpf_get_current_pid_tgid();
+	uint32_t real_tgid = (uint32_t)pid_tgid;
 	int pid, tgid;
 
 	if (CORE_READ(&pid, &task->pid) ||
@@ -32,7 +42,49 @@ int test_core_kernel(void *ctx)
 		return 1;
 
 	/* validate pid + tgid matches */
-	data.out[0] = (((uint64_t)pid << 32) | tgid) == pid_tgid;
+	out->valid[0] = (((uint64_t)pid << 32) | tgid) == pid_tgid;
+
+	/* test variadic BPF_CORE_READ macros */
+	out->valid[1] = BPF_CORE_READ(task,
+				      tgid) == real_tgid;
+	out->valid[2] = BPF_CORE_READ(task,
+				      group_leader,
+				      tgid) == real_tgid;
+	out->valid[3] = BPF_CORE_READ(task,
+				      group_leader, group_leader,
+				      tgid) == real_tgid;
+	out->valid[4] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      tgid) == real_tgid;
+	out->valid[5] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      group_leader,
+				      tgid) == real_tgid;
+	out->valid[6] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      group_leader, group_leader,
+				      tgid) == real_tgid;
+	out->valid[7] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      group_leader, group_leader, group_leader,
+				      tgid) == real_tgid;
+	out->valid[8] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      group_leader, group_leader, group_leader,
+				      group_leader,
+				      tgid) == real_tgid;
+	out->valid[9] = BPF_CORE_READ(task,
+				      group_leader, group_leader, group_leader,
+				      group_leader, group_leader, group_leader,
+				      group_leader, group_leader,
+				      tgid) == real_tgid;
+
+	/* test BPF_CORE_READ_STR_INTO() returns correct code and contents */
+	out->comm_len = BPF_CORE_READ_STR_INTO(
+		&out->comm, task,
+		group_leader, group_leader, group_leader, group_leader,
+		group_leader, group_leader, group_leader, group_leader,
+		comm);
 
 	return 0;
 }