selftests/bpf: Add tests for bpf_find_vma

Add tests for bpf_find_vma in perf_event program and kprobe program. The
perf_event program is triggered from NMI context, so the second call of
bpf_find_vma() will return -EBUSY (irq_work busy). The kprobe program,
on the other hand, does not have this constraint.

Also add tests for illegal writes to task or vma from the callback
function. The verifier should reject both cases.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211105232330.1936330-3-songliubraving@fb.com

1 files changed, 69 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/find_vma.c b/tools/testing/selftests/bpf/progs/find_vma.c
new file mode 100644
index 000000000000..38034fb82530
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/find_vma.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct callback_ctx {
+	int dummy;
+};
+
+#define VM_EXEC		0x00000004
+#define DNAME_INLINE_LEN 32
+
+pid_t target_pid = 0;
+char d_iname[DNAME_INLINE_LEN] = {0};
+__u32 found_vm_exec = 0;
+__u64 addr = 0;
+int find_zero_ret = -1;
+int find_addr_ret = -1;
+
+static long check_vma(struct task_struct *task, struct vm_area_struct *vma,
+		      struct callback_ctx *data)
+{
+	if (vma->vm_file)
+		bpf_probe_read_kernel_str(d_iname, DNAME_INLINE_LEN - 1,
+					  vma->vm_file->f_path.dentry->d_iname);
+
+	/* check for VM_EXEC */
+	if (vma->vm_flags & VM_EXEC)
+		found_vm_exec = 1;
+
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+int handle_getpid(void)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+	struct callback_ctx data = {};
+
+	if (task->pid != target_pid)
+		return 0;
+
+	find_addr_ret = bpf_find_vma(task, addr, check_vma, &data, 0);
+
+	/* this should return -ENOENT */
+	find_zero_ret = bpf_find_vma(task, 0, check_vma, &data, 0);
+	return 0;
+}
+
+SEC("perf_event")
+int handle_pe(void)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+	struct callback_ctx data = {};
+
+	if (task->pid != target_pid)
+		return 0;
+
+	find_addr_ret = bpf_find_vma(task, addr, check_vma, &data, 0);
+
+	/* In NMI, this should return -EBUSY, as the previous call is using
+	 * the irq_work.
+	 */
+	find_zero_ret = bpf_find_vma(task, 0, check_vma, &data, 0);
+	return 0;
+}