Re: [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf
On Thu, Apr 15, 2021 at 12:16 AM Andrii Nakryiko wrote: > > On Wed, Apr 14, 2021 at 2:21 AM Florent Revest wrote: > > > > On Wed, Apr 14, 2021 at 1:21 AM Andrii Nakryiko > > wrote: > > > > > > On Mon, Apr 12, 2021 at 8:38 AM Florent Revest > > > wrote: > > > > > > > > This exercises most of the format specifiers. > > > > > > > > Signed-off-by: Florent Revest > > > > Acked-by: Andrii Nakryiko > > > > --- > > > > > > As I mentioned on another patch, we probably need negative tests even > > > more than positive ones. > > > > Agreed. > > > > > I think an easy and nice way to do this is to have a separate BPF > > > skeleton where fmt string and arguments are provided through read-only > > > global variables, so that user-space can re-use the same BPF skeleton > > > to simulate multiple cases. BPF program itself would just call > > > bpf_snprintf() and store the returned result. > > > > Ah, great idea! I was thinking of having one skeleton for each but it > > would be a bit much indeed. > > > > Because the format string needs to be in a read only map though, I > > hope it can be modified from userspace before loading. I'll try it out > > and see :) if it doesn't work I'll just use more skeletons > > You need read-only variables (const volatile my_type). Their contents > are statically verified by BPF verifier, yet user-space can pre-setup > it at runtime. Thanks :) v4 has negative fmt tests
Re: [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf
On Wed, Apr 14, 2021 at 2:21 AM Florent Revest wrote: > > On Wed, Apr 14, 2021 at 1:21 AM Andrii Nakryiko > wrote: > > > > On Mon, Apr 12, 2021 at 8:38 AM Florent Revest wrote: > > > > > > This exercises most of the format specifiers. > > > > > > Signed-off-by: Florent Revest > > > Acked-by: Andrii Nakryiko > > > --- > > > > As I mentioned on another patch, we probably need negative tests even > > more than positive ones. > > Agreed. > > > I think an easy and nice way to do this is to have a separate BPF > > skeleton where fmt string and arguments are provided through read-only > > global variables, so that user-space can re-use the same BPF skeleton > > to simulate multiple cases. BPF program itself would just call > > bpf_snprintf() and store the returned result. > > Ah, great idea! I was thinking of having one skeleton for each but it > would be a bit much indeed. > > Because the format string needs to be in a read only map though, I > hope it can be modified from userspace before loading. I'll try it out > and see :) if it doesn't work I'll just use more skeletons You need read-only variables (const volatile my_type). Their contents are statically verified by BPF verifier, yet user-space can pre-setup it at runtime. > > > Whether we need to validate the verifier log is up to debate (though > > it's not that hard to do by overriding libbpf_print_fn() callback), > > I'd be ok at least knowing that some bad format strings are rejected > > and don't crash the kernel. > > Alright :) > > > > > > .../selftests/bpf/prog_tests/snprintf.c | 81 +++ > > > .../selftests/bpf/progs/test_snprintf.c | 74 + > > > 2 files changed, 155 insertions(+) > > > create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c > > > create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c > > > > > > > [...]
Re: [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf
On Wed, Apr 14, 2021 at 1:21 AM Andrii Nakryiko wrote: > > On Mon, Apr 12, 2021 at 8:38 AM Florent Revest wrote: > > > > This exercises most of the format specifiers. > > > > Signed-off-by: Florent Revest > > Acked-by: Andrii Nakryiko > > --- > > As I mentioned on another patch, we probably need negative tests even > more than positive ones. Agreed. > I think an easy and nice way to do this is to have a separate BPF > skeleton where fmt string and arguments are provided through read-only > global variables, so that user-space can re-use the same BPF skeleton > to simulate multiple cases. BPF program itself would just call > bpf_snprintf() and store the returned result. Ah, great idea! I was thinking of having one skeleton for each but it would be a bit much indeed. Because the format string needs to be in a read only map though, I hope it can be modified from userspace before loading. I'll try it out and see :) if it doesn't work I'll just use more skeletons > Whether we need to validate the verifier log is up to debate (though > it's not that hard to do by overriding libbpf_print_fn() callback), > I'd be ok at least knowing that some bad format strings are rejected > and don't crash the kernel. Alright :) > > > .../selftests/bpf/prog_tests/snprintf.c | 81 +++ > > .../selftests/bpf/progs/test_snprintf.c | 74 + > > 2 files changed, 155 insertions(+) > > create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c > > create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c > > > > [...]
Re: [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf
On Mon, Apr 12, 2021 at 8:38 AM Florent Revest wrote: > > This exercises most of the format specifiers. > > Signed-off-by: Florent Revest > Acked-by: Andrii Nakryiko > --- As I mentioned on another patch, we probably need negative tests even more than positive ones. I think an easy and nice way to do this is to have a separate BPF skeleton where fmt string and arguments are provided through read-only global variables, so that user-space can re-use the same BPF skeleton to simulate multiple cases. BPF program itself would just call bpf_snprintf() and store the returned result. Whether we need to validate the verifier log is up to debate (though it's not that hard to do by overriding libbpf_print_fn() callback), I'd be ok at least knowing that some bad format strings are rejected and don't crash the kernel. > .../selftests/bpf/prog_tests/snprintf.c | 81 +++ > .../selftests/bpf/progs/test_snprintf.c | 74 + > 2 files changed, 155 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c > create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c > [...]
[PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf
This exercises most of the format specifiers.
Signed-off-by: Florent Revest
Acked-by: Andrii Nakryiko
---
.../selftests/bpf/prog_tests/snprintf.c | 81 +++
.../selftests/bpf/progs/test_snprintf.c | 74 +
2 files changed, 155 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c
diff --git a/tools/testing/selftests/bpf/prog_tests/snprintf.c
b/tools/testing/selftests/bpf/prog_tests/snprintf.c
new file mode 100644
index ..3ad1ee885273
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/snprintf.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Google LLC. */
+
+#include
+#include "test_snprintf.skel.h"
+
+#define EXP_NUM_OUT "-8 9 96 -424242 1337 DABBAD00"
+#define EXP_NUM_RET sizeof(EXP_NUM_OUT)
+
+#define EXP_IP_OUT "127.000.000.001 :::::::0001"
+#define EXP_IP_RET sizeof(EXP_IP_OUT)
+
+/* The third specifier, %pB, depends on compiler inlining so don't check it */
+#define EXP_SYM_OUT "schedule schedule+0x0/"
+#define MIN_SYM_RET sizeof(EXP_SYM_OUT)
+
+/* The third specifier, %p, is a hashed pointer which changes on every reboot
*/
+#define EXP_ADDR_OUT " 0add4e55 "
+#define EXP_ADDR_RET sizeof(EXP_ADDR_OUT "unknownhashedptr")
+
+#define EXP_STR_OUT "str1 longstr"
+#define EXP_STR_RET sizeof(EXP_STR_OUT)
+
+#define EXP_OVER_OUT "%over"
+#define EXP_OVER_RET 10
+
+#define EXP_PAD_OUT "4 000"
+#define EXP_PAD_RET 97
+
+#define EXP_NO_ARG_OUT "simple case"
+#define EXP_NO_ARG_RET 12
+
+#define EXP_NO_BUF_RET 29
+
+void test_snprintf(void)
+{
+ char exp_addr_out[] = EXP_ADDR_OUT;
+ char exp_sym_out[] = EXP_SYM_OUT;
+ struct test_snprintf *skel;
+
+ skel = test_snprintf__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+
+ if (!ASSERT_OK(test_snprintf__attach(skel), "skel_attach"))
+ goto cleanup;
+
+ /* trigger tracepoint */
+ usleep(1);
+
+ ASSERT_STREQ(skel->bss->num_out, EXP_NUM_OUT, "num_out");
+ ASSERT_EQ(skel->bss->num_ret, EXP_NUM_RET, "num_ret");
+
+ ASSERT_STREQ(skel->bss->ip_out, EXP_IP_OUT, "ip_out");
+ ASSERT_EQ(skel->bss->ip_ret, EXP_IP_RET, "ip_ret");
+
+ ASSERT_OK(memcmp(skel->bss->sym_out, exp_sym_out,
+sizeof(exp_sym_out) - 1), "sym_out");
+ ASSERT_LT(MIN_SYM_RET, skel->bss->sym_ret, "sym_ret");
+
+ ASSERT_OK(memcmp(skel->bss->addr_out, exp_addr_out,
+sizeof(exp_addr_out) - 1), "addr_out");
+ ASSERT_EQ(skel->bss->addr_ret, EXP_ADDR_RET, "addr_ret");
+
+ ASSERT_STREQ(skel->bss->str_out, EXP_STR_OUT, "str_out");
+ ASSERT_EQ(skel->bss->str_ret, EXP_STR_RET, "str_ret");
+
+ ASSERT_STREQ(skel->bss->over_out, EXP_OVER_OUT, "over_out");
+ ASSERT_EQ(skel->bss->over_ret, EXP_OVER_RET, "over_ret");
+
+ ASSERT_STREQ(skel->bss->pad_out, EXP_PAD_OUT, "pad_out");
+ ASSERT_EQ(skel->bss->pad_ret, EXP_PAD_RET, "pad_ret");
+
+ ASSERT_STREQ(skel->bss->noarg_out, EXP_NO_ARG_OUT, "no_arg_out");
+ ASSERT_EQ(skel->bss->noarg_ret, EXP_NO_ARG_RET, "no_arg_ret");
+
+ ASSERT_EQ(skel->bss->nobuf_ret, EXP_NO_BUF_RET, "no_buf_ret");
+
+cleanup:
+ test_snprintf__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_snprintf.c
b/tools/testing/selftests/bpf/progs/test_snprintf.c
new file mode 100644
index ..4c36f355dfca
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_snprintf.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Google LLC. */
+
+#include
+#include
+#include
+#include
+
+char num_out[64] = {};
+long num_ret = 0;
+
+char ip_out[64] = {};
+long ip_ret = 0;
+
+char sym_out[64] = {};
+long sym_ret = 0;
+
+char addr_out[64] = {};
+long addr_ret = 0;
+
+char str_out[64] = {};
+long str_ret = 0;
+
+char over_out[6] = {};
+long over_ret = 0;
+
+char pad_out[10] = {};
+long pad_ret = 0;
+
+char noarg_out[64] = {};
+long noarg_ret = 0;
+
+long nobuf_ret = 0;
+
+extern const void schedule __ksym;
+
+SEC("raw_tp/sys_enter")
+int handler(const void *ctx)
+{
+ /* Convenient values to pretty-print */
+ const __u8 ex_ipv4[] = {127, 0, 0, 1};
+ const __u8 ex_ipv6[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
+ const char str1[] = "str1";
+ const char longstr[] = "longstr";
+
+ /* Integer types */
+ num_ret = BPF_SNPRINTF(num_out, sizeof(num_out),
+ "%d %u %x %li %llu %lX",
+ -8, 9, 150, -424242, 1337, 0xDABBAD00);
+ /* IP addresses */
+ ip_ret = BPF_SNPRINTF(ip_out, sizeof(ip_out), "%pi4 %pI6",
+ _ipv4, _ipv6);
+ /* Symbol lookup formatting */
+ sym_ret = BPF_SNPRINTF(sym_out,
