On 12/16/22 10:31 AM, Dave Marchevsky wrote:
This patch adds a test exercising logic that was fixed / improved in
the previous patch in the series, as well as general sanity checking for
jit's PROBE_MEM logic which should've been unaffected by the previous
patch.
The added verifier test does the following:
* Acquire a referenced kptr to struct prog_test_ref_kfunc using
existing net/bpf/test_run.c kfunc
* Helper returns ptr to a specific prog_test_ref_kfunc whose first
two fields - both ints - have been prepopulated w/ vals 42 and
108, respectively
* kptr_xchg the acquired ptr into an arraymap
* Do a direct map_value load of the just-added ptr
* Goal of all this setup is to get an unreferenced kptr pointing to
struct with ints of known value, which is the result of this step
* Using unreferenced kptr obtained in previous step, do loads of
prog_test_ref_kfunc.a (offset 0) and .b (offset 4)
* Then incr the kptr by 8 and load prog_test_ref_kfunc.a again (this
time at offset -8)
* Add all the loaded ints together and return
Before the PROBE_MEM fixes in previous patch, the loads at offset 0 and
4 would succeed, while the load at offset -8 would incorrectly fail
runtime check emitted by the JIT and 0 out dst reg as a result. This
confirmed by retval of 150 for this test before previous patch - since
second .a read is 0'd out - and a retval of 192 with the fixed logic.
The test exercises the two optimizations to fixed logic added in last
patch as well:
* First load, with insn "r8 = *(u32 *)(r9 + 0)" exercises "insn->off
is 0, no need to add / sub from src_reg" optimization
* Third load, with insn "r9 = *(u32 *)(r9 - 8)" exercises "src_reg ==
dst_reg, no need to restore src_reg after load" optimization
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
Ack with one nit below.
Acked-by: Yonghong Song <yhs@xxxxxx>
---
v1 -> v2: lore.kernel.org/bpf/20221213182726.325137-2-davemarchevsky@xxxxxx
* Rewrite the test to be a "normal" C prog in selftests/bpf/progs. Result
is a much easier-to-understand test with assembly used only for the 3
loads. (Yonghong)
.../selftests/bpf/prog_tests/jit_probe_mem.c | 28 +++++++++
.../selftests/bpf/progs/jit_probe_mem.c | 61 +++++++++++++++++++
2 files changed, 89 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/jit_probe_mem.c
create mode 100644 tools/testing/selftests/bpf/progs/jit_probe_mem.c
diff --git a/tools/testing/selftests/bpf/prog_tests/jit_probe_mem.c b/tools/testing/selftests/bpf/prog_tests/jit_probe_mem.c
new file mode 100644
index 000000000000..5639428607e6
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/jit_probe_mem.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "jit_probe_mem.skel.h"
+
+void test_jit_probe_mem(void)
+{
+ LIBBPF_OPTS(bpf_test_run_opts, opts,
+ .data_in = &pkt_v4,
+ .data_size_in = sizeof(pkt_v4),
+ .repeat = 1,
+ );
+ struct jit_probe_mem *skel;
+ int ret;
+
+ skel = jit_probe_mem__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "jit_probe_mem__open_and_load"))
+ return;
+
+ ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_jit_probe_mem), &opts);
+ ASSERT_OK(ret, "jit_probe_mem ret");
+ ASSERT_OK(opts.retval, "jit_probe_mem opts.retval");
+ ASSERT_EQ(skel->data->total_sum, 192, "jit_probe_mem total_sum");
+
+ jit_probe_mem__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/jit_probe_mem.c b/tools/testing/selftests/bpf/progs/jit_probe_mem.c
new file mode 100644
index 000000000000..3bb8af4df837
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/jit_probe_mem.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+static struct prog_test_ref_kfunc __kptr_ref *v;
+long total_sum = -1;
+
+extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
+extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+
+SEC("tc")
+int test_jit_probe_mem(struct __sk_buff *ctx)
+{
+ struct prog_test_ref_kfunc *p;
+ unsigned long zero = 0, sum;
+
+ p = bpf_kfunc_call_test_acquire(&zero);
+ if (!p)
+ return 1;
+
+ p = bpf_kptr_xchg(&v, p);
+ if (p)
+ goto release_out;
+
+ /* Direct map value access of kptr, should be PTR_UNTRUSTED */
+ p = v;
+ if (!p)
+ return 1;
+
+ asm volatile (
+ "r9 = %[p];\n"
+ "%[sum] = 0;\n"
+
+ /* r8 = p->a */
+ "r8 = *(u32 *)(r9 + 0);\n"
+ "%[sum] += r8;\n"
+
+ /* r8 = p->b */
+ "r8 = *(u32 *)(r9 + 4);\n"
+ "%[sum] += r8;\n"
+
+ "r9 += 8;\n"
+ /* r9 = p->a */
+ "r9 = *(u32 *)(r9 - 8);\n"
+ "%[sum] += r9;\n"
All these '\n' are not necessary.
+
+ : [sum] "=r"(sum)
+ : [p] "r"(p)
+ : "r8", "r9"
+ );
+
+ total_sum = sum;
+ return 0;
+release_out:
+ bpf_kfunc_call_test_release(p);
+ return 1;
+}
+
+char _license[] SEC("license") = "GPL";
