[PATCH bpf-next v4 3/3] selftests/bpf: Add tests for arena fault reporting

[Puranjay Mohan <puranjay@kernel.org>]

Add selftests for testing the reporting of arena page faults through BPF
streams. Two new bpf programs are added that read and write to an
unmapped arena address and the fault reporting is verified in the
userspace through streams.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/stream.c | 33 +++++++++++++++-
 tools/testing/selftests/bpf/progs/stream.c    | 39 +++++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/stream.c b/tools/testing/selftests/bpf/prog_tests/stream.c
index 36a1a1ebde692..8fdc83260ea14 100644
--- a/tools/testing/selftests/bpf/prog_tests/stream.c
+++ b/tools/testing/selftests/bpf/prog_tests/stream.c
@@ -41,6 +41,22 @@ struct {
 		"([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
 		"|[ \t]+[^\n]+\n)*",
 	},
+	{
+		offsetof(struct stream, progs.stream_arena_read_fault),
+		"ERROR: Arena READ access at unmapped address 0x.*\n"
+		"CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n"
+		"Call trace:\n"
+		"([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
+		"|[ \t]+[^\n]+\n)*",
+	},
+	{
+		offsetof(struct stream, progs.stream_arena_write_fault),
+		"ERROR: Arena WRITE access at unmapped address 0x.*\n"
+		"CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n"
+		"Call trace:\n"
+		"([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n"
+		"|[ \t]+[^\n]+\n)*",
+	},
 };
 
 static int match_regex(const char *pattern, const char *string)
@@ -63,6 +79,7 @@ void test_stream_errors(void)
 	struct stream *skel;
 	int ret, prog_fd;
 	char buf[1024];
+	char fault_addr[64] = {0};
 
 	skel = stream__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
@@ -85,6 +102,14 @@ void test_stream_errors(void)
 			continue;
 		}
 #endif
+#if !defined(__x86_64__) && !defined(__aarch64__)
+		ASSERT_TRUE(1, "Arena fault reporting unsupported, skip.");
+		if (i == 2 || i == 3) {
+			ret = bpf_prog_stream_read(prog_fd, 2, buf, sizeof(buf), &ropts);
+			ASSERT_EQ(ret, 0, "stream read");
+			continue;
+		}
+#endif
 
 		ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, buf, sizeof(buf), &ropts);
 		ASSERT_GT(ret, 0, "stream read");
@@ -92,8 +117,14 @@ void test_stream_errors(void)
 		buf[ret] = '\0';
 
 		ret = match_regex(stream_error_arr[i].errstr, buf);
-		if (!ASSERT_TRUE(ret == 1, "regex match"))
+		if (ret && (i == 2 || i == 3)) {
+			sprintf(fault_addr, "0x%lx", skel->bss->fault_addr);
+			ret = match_regex(fault_addr, buf);
+		}
+		if (!ASSERT_TRUE(ret == 1, "regex match")) {
 			fprintf(stderr, "Output from stream:\n%s\n", buf);
+			fprintf(stderr, "Fault Addr: 0x%lx\n", skel->bss->fault_addr);
+		}
 	}
 
 	stream__destroy(skel);
diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c
index 35790897dc879..9de015ac3ced5 100644
--- a/tools/testing/selftests/bpf/progs/stream.c
+++ b/tools/testing/selftests/bpf/progs/stream.c
@@ -5,6 +5,7 @@
 #include <bpf/bpf_helpers.h>
 #include "bpf_misc.h"
 #include "bpf_experimental.h"
+#include "bpf_arena_common.h"
 
 struct arr_elem {
 	struct bpf_res_spin_lock lock;
@@ -17,10 +18,17 @@ struct {
 	__type(value, struct arr_elem);
 } arrmap SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_ARENA);
+	__uint(map_flags, BPF_F_MMAPABLE);
+	__uint(max_entries, 1); /* number of pages */
+} arena SEC(".maps");
+
 #define ENOSPC 28
 #define _STR "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
 
 int size;
+u64 fault_addr;
 
 SEC("syscall")
 __success __retval(0)
@@ -76,4 +84,35 @@ int stream_syscall(void *ctx)
 	return 0;
 }
 
+SEC("syscall")
+__success __retval(0)
+int stream_arena_write_fault(void *ctx)
+{
+	struct bpf_arena *ptr = (void *)&arena;
+	u64 user_vm_start;
+
+	barrier_var(ptr);
+	user_vm_start =  ptr->user_vm_start;
+
+	fault_addr = user_vm_start + 0xbeef;
+	*(u32 __arena *)(user_vm_start + 0xbeef) = 1;
+
+	return 0;
+}
+
+SEC("syscall")
+__success __retval(0)
+int stream_arena_read_fault(void *ctx)
+{
+	struct bpf_arena *ptr = (void *)&arena;
+	u64 user_vm_start;
+
+	barrier_var(ptr);
+	user_vm_start =  ptr->user_vm_start;
+
+	fault_addr = user_vm_start + 0xbeef;
+
+	return *(u32 __arena *)(user_vm_start + 0xbeef);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.47.3