diff mbox series

[bpf-next,v1,5/8] bpf/selftests: ksyms_btf to test typed ksyms

Message ID 20200819224030.1615203-6-haoluo@google.com
State New
Headers show
Series bpf: BTF support for ksyms | expand

Commit Message

Hao Luo Aug. 19, 2020, 10:40 p.m. UTC
Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
the other is a plain int. This tests two paths in the kernel. Struct
ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
typed ksyms will be converted into PTR_TO_MEM.

Signed-off-by: Hao Luo <haoluo@google.com>
---
 .../selftests/bpf/prog_tests/ksyms_btf.c      | 77 +++++++++++++++++++
 .../selftests/bpf/progs/test_ksyms_btf.c      | 23 ++++++
 2 files changed, 100 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c

Comments

Yonghong Song Aug. 20, 2020, 5:28 p.m. UTC | #1
On 8/19/20 3:40 PM, Hao Luo wrote:
> Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
> the other is a plain int. This tests two paths in the kernel. Struct
> ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
> typed ksyms will be converted into PTR_TO_MEM.
> 
> Signed-off-by: Hao Luo <haoluo@google.com>
> ---
>   .../selftests/bpf/prog_tests/ksyms_btf.c      | 77 +++++++++++++++++++
>   .../selftests/bpf/progs/test_ksyms_btf.c      | 23 ++++++
>   2 files changed, 100 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> new file mode 100644
> index 000000000000..1dad61ba7e99
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> @@ -0,0 +1,77 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Google */
> +
> +#include <test_progs.h>
> +#include <bpf/libbpf.h>
> +#include <bpf/btf.h>
> +#include "test_ksyms_btf.skel.h"
> +
> +static int duration;
> +
> +static __u64 kallsyms_find(const char *sym)
> +{
> +	char type, name[500];
> +	__u64 addr, res = 0;
> +	FILE *f;
> +
> +	f = fopen("/proc/kallsyms", "r");
> +	if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
> +		return 0;

could you check whether libbpf API can provide this functionality for 
you? As far as I know, libbpf does parse /proc/kallsyms.

> +
> +	while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) {
> +		if (strcmp(name, sym) == 0) {
> +			res = addr;
> +			goto out;
> +		}
> +	}
> +
> +	CHECK(false, "not_found", "symbol %s not found\n", sym);
> +out:
> +	fclose(f);
> +	return res;
> +}
> +
> +void test_ksyms_btf(void)
> +{
> +	__u64 runqueues_addr = kallsyms_find("runqueues");
> +	__u64 bpf_prog_active_addr = kallsyms_find("bpf_prog_active");
> +	struct test_ksyms_btf *skel;
> +	struct test_ksyms_btf__data *data;
> +	struct btf *btf;
> +	int percpu_datasec;
> +	int err;
> +
> +	btf = libbpf_find_kernel_btf();
> +	if (CHECK(IS_ERR(btf), "btf_exists", "failed to load kernel BTF: %ld\n",
> +		  PTR_ERR(btf)))
> +		return;
> +
> +	percpu_datasec = btf__find_by_name_kind(btf, ".data..percpu",
> +						BTF_KIND_DATASEC);
> +	if (percpu_datasec < 0) {
> +		printf("%s:SKIP:no PERCPU DATASEC in kernel btf\n",
> +		       __func__);
> +		test__skip();
> +		return;
> +	}
> +
> +	skel = test_ksyms_btf__open_and_load();
> +	if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n"))
> +		return;
> +
> +	err = test_ksyms_btf__attach(skel);
> +	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
> +		goto cleanup;
> +
> +	/* trigger tracepoint */
> +	usleep(1);
> +
> +	data = skel->data;
> +	CHECK(data->out__runqueues != runqueues_addr, "runqueues",
> +	      "got %llu, exp %llu\n", data->out__runqueues, runqueues_addr);
> +	CHECK(data->out__bpf_prog_active != bpf_prog_active_addr, "bpf_prog_active",
> +	      "got %llu, exp %llu\n", data->out__bpf_prog_active, bpf_prog_active_addr);
> +
> +cleanup:
> +	test_ksyms_btf__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> new file mode 100644
> index 000000000000..e04e31117f84
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Google */
> +
> +#include "vmlinux.h"
> +
> +#include <bpf/bpf_helpers.h>
> +
> +__u64 out__runqueues = -1;
> +__u64 out__bpf_prog_active = -1;
> +
> +extern const struct rq runqueues __ksym; /* struct type global var. */
> +extern const int bpf_prog_active __ksym; /* int type global var. */
> +
> +SEC("raw_tp/sys_enter")
> +int handler(const void *ctx)
> +{
> +	out__runqueues = (__u64)&runqueues;
> +	out__bpf_prog_active = (__u64)&bpf_prog_active;
> +
> +	return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
>
Andrii Nakryiko Aug. 21, 2020, 11:03 p.m. UTC | #2
On Thu, Aug 20, 2020 at 10:32 AM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 8/19/20 3:40 PM, Hao Luo wrote:
> > Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
> > the other is a plain int. This tests two paths in the kernel. Struct
> > ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
> > typed ksyms will be converted into PTR_TO_MEM.
> >
> > Signed-off-by: Hao Luo <haoluo@google.com>
> > ---
> >   .../selftests/bpf/prog_tests/ksyms_btf.c      | 77 +++++++++++++++++++
> >   .../selftests/bpf/progs/test_ksyms_btf.c      | 23 ++++++
> >   2 files changed, 100 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> >   create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > new file mode 100644
> > index 000000000000..1dad61ba7e99
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > @@ -0,0 +1,77 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2020 Google */
> > +
> > +#include <test_progs.h>
> > +#include <bpf/libbpf.h>
> > +#include <bpf/btf.h>
> > +#include "test_ksyms_btf.skel.h"
> > +
> > +static int duration;
> > +
> > +static __u64 kallsyms_find(const char *sym)
> > +{
> > +     char type, name[500];
> > +     __u64 addr, res = 0;
> > +     FILE *f;
> > +
> > +     f = fopen("/proc/kallsyms", "r");
> > +     if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
> > +             return 0;
>
> could you check whether libbpf API can provide this functionality for
> you? As far as I know, libbpf does parse /proc/kallsyms.

No need to use libbpf's implementation. We already have
kallsyms_find() in prog_tests/ksyms.c and a combination of
load_kallsyms() + ksym_get_addr() in trace_helpers.c. It would be good
to switch to one implementation for both prog_tests/ksyms.c and this
one.


>
> > +
> > +     while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) {
> > +             if (strcmp(name, sym) == 0) {
> > +                     res = addr;
> > +                     goto out;
> > +             }
> > +     }
> > +

[...]

> > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > new file mode 100644
> > index 000000000000..e04e31117f84
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > @@ -0,0 +1,23 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2020 Google */
> > +
> > +#include "vmlinux.h"
> > +
> > +#include <bpf/bpf_helpers.h>
> > +
> > +__u64 out__runqueues = -1;
> > +__u64 out__bpf_prog_active = -1;
> > +
> > +extern const struct rq runqueues __ksym; /* struct type global var. */
> > +extern const int bpf_prog_active __ksym; /* int type global var. */
> > +
> > +SEC("raw_tp/sys_enter")
> > +int handler(const void *ctx)
> > +{
> > +     out__runqueues = (__u64)&runqueues;
> > +     out__bpf_prog_active = (__u64)&bpf_prog_active;
> > +

You didn't test accessing any of the members of runqueues, because BTF
only has per-CPU variables, right? Adding global/static variables was
adding too much data to BTF or something like that, is that right?

> > +     return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> >
Hao Luo Aug. 22, 2020, 7:26 a.m. UTC | #3
On Fri, Aug 21, 2020 at 4:03 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Thu, Aug 20, 2020 at 10:32 AM Yonghong Song <yhs@fb.com> wrote:
> >
> >
> >
> > On 8/19/20 3:40 PM, Hao Luo wrote:
> > > Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
> > > the other is a plain int. This tests two paths in the kernel. Struct
> > > ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
> > > typed ksyms will be converted into PTR_TO_MEM.
> > >
> > > Signed-off-by: Hao Luo <haoluo@google.com>
> > > ---
> > >   .../selftests/bpf/prog_tests/ksyms_btf.c      | 77 +++++++++++++++++++
> > >   .../selftests/bpf/progs/test_ksyms_btf.c      | 23 ++++++
> > >   2 files changed, 100 insertions(+)
> > >   create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > >   create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > > new file mode 100644
> > > index 000000000000..1dad61ba7e99
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > > @@ -0,0 +1,77 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/* Copyright (c) 2020 Google */
> > > +
> > > +#include <test_progs.h>
> > > +#include <bpf/libbpf.h>
> > > +#include <bpf/btf.h>
> > > +#include "test_ksyms_btf.skel.h"
> > > +
> > > +static int duration;
> > > +
> > > +static __u64 kallsyms_find(const char *sym)
> > > +{
> > > +     char type, name[500];
> > > +     __u64 addr, res = 0;
> > > +     FILE *f;
> > > +
> > > +     f = fopen("/proc/kallsyms", "r");
> > > +     if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
> > > +             return 0;
> >
> > could you check whether libbpf API can provide this functionality for
> > you? As far as I know, libbpf does parse /proc/kallsyms.
>
> No need to use libbpf's implementation. We already have
> kallsyms_find() in prog_tests/ksyms.c and a combination of
> load_kallsyms() + ksym_get_addr() in trace_helpers.c. It would be good
> to switch to one implementation for both prog_tests/ksyms.c and this
> one.
>
Ack. I can do some refactoring. The least thing that I can do is
moving kallsyms_find() to a header for both prog_tests/ksyms.c and
this test to use.

>
> > > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > > new file mode 100644
> > > index 000000000000..e04e31117f84
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > > @@ -0,0 +1,23 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/* Copyright (c) 2020 Google */
> > > +
> > > +#include "vmlinux.h"
> > > +
> > > +#include <bpf/bpf_helpers.h>
> > > +
> > > +__u64 out__runqueues = -1;
> > > +__u64 out__bpf_prog_active = -1;
> > > +
> > > +extern const struct rq runqueues __ksym; /* struct type global var. */
> > > +extern const int bpf_prog_active __ksym; /* int type global var. */
> > > +
> > > +SEC("raw_tp/sys_enter")
> > > +int handler(const void *ctx)
> > > +{
> > > +     out__runqueues = (__u64)&runqueues;
> > > +     out__bpf_prog_active = (__u64)&bpf_prog_active;
> > > +
>
> You didn't test accessing any of the members of runqueues, because BTF
> only has per-CPU variables, right? Adding global/static variables was
> adding too much data to BTF or something like that, is that right?
>

Right. With some experiments, I found the address of a percpu variable
doesn't necessarily point to a valid structure. So it doesn't make
sense to dereference runqueues and access its members. However, right
now there are only percpu variables encoded in BTF, so I can't test
accessing members of general global/static variables unfortunately.

Hao
Andrii Nakryiko Aug. 22, 2020, 7:35 a.m. UTC | #4
On Sat, Aug 22, 2020 at 12:27 AM Hao Luo <haoluo@google.com> wrote:
>
> On Fri, Aug 21, 2020 at 4:03 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Thu, Aug 20, 2020 at 10:32 AM Yonghong Song <yhs@fb.com> wrote:
> > >
> > >
> > >
> > > On 8/19/20 3:40 PM, Hao Luo wrote:
> > > > Selftests for typed ksyms. Tests two types of ksyms: one is a struct,
> > > > the other is a plain int. This tests two paths in the kernel. Struct
> > > > ksyms will be converted into PTR_TO_BTF_ID by the verifier while int
> > > > typed ksyms will be converted into PTR_TO_MEM.
> > > >
> > > > Signed-off-by: Hao Luo <haoluo@google.com>
> > > > ---
> > > >   .../selftests/bpf/prog_tests/ksyms_btf.c      | 77 +++++++++++++++++++
> > > >   .../selftests/bpf/progs/test_ksyms_btf.c      | 23 ++++++
> > > >   2 files changed, 100 insertions(+)
> > > >   create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > > >   create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > > >
> > > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > > > new file mode 100644
> > > > index 000000000000..1dad61ba7e99
> > > > --- /dev/null
> > > > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> > > > @@ -0,0 +1,77 @@
> > > > +// SPDX-License-Identifier: GPL-2.0
> > > > +/* Copyright (c) 2020 Google */
> > > > +
> > > > +#include <test_progs.h>
> > > > +#include <bpf/libbpf.h>
> > > > +#include <bpf/btf.h>
> > > > +#include "test_ksyms_btf.skel.h"
> > > > +
> > > > +static int duration;
> > > > +
> > > > +static __u64 kallsyms_find(const char *sym)
> > > > +{
> > > > +     char type, name[500];
> > > > +     __u64 addr, res = 0;
> > > > +     FILE *f;
> > > > +
> > > > +     f = fopen("/proc/kallsyms", "r");
> > > > +     if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
> > > > +             return 0;
> > >
> > > could you check whether libbpf API can provide this functionality for
> > > you? As far as I know, libbpf does parse /proc/kallsyms.
> >
> > No need to use libbpf's implementation. We already have
> > kallsyms_find() in prog_tests/ksyms.c and a combination of
> > load_kallsyms() + ksym_get_addr() in trace_helpers.c. It would be good
> > to switch to one implementation for both prog_tests/ksyms.c and this
> > one.
> >
> Ack. I can do some refactoring. The least thing that I can do is
> moving kallsyms_find() to a header for both prog_tests/ksyms.c and
> this test to use.

Please no extra headers. Just put kallsyms_find() in trace_helpers.c,
along other kallsyms-related functions.

>
> >
> > > > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > > > new file mode 100644
> > > > index 000000000000..e04e31117f84
> > > > --- /dev/null
> > > > +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> > > > @@ -0,0 +1,23 @@
> > > > +// SPDX-License-Identifier: GPL-2.0
> > > > +/* Copyright (c) 2020 Google */
> > > > +
> > > > +#include "vmlinux.h"
> > > > +
> > > > +#include <bpf/bpf_helpers.h>
> > > > +
> > > > +__u64 out__runqueues = -1;
> > > > +__u64 out__bpf_prog_active = -1;
> > > > +
> > > > +extern const struct rq runqueues __ksym; /* struct type global var. */
> > > > +extern const int bpf_prog_active __ksym; /* int type global var. */
> > > > +
> > > > +SEC("raw_tp/sys_enter")
> > > > +int handler(const void *ctx)
> > > > +{
> > > > +     out__runqueues = (__u64)&runqueues;
> > > > +     out__bpf_prog_active = (__u64)&bpf_prog_active;
> > > > +
> >
> > You didn't test accessing any of the members of runqueues, because BTF
> > only has per-CPU variables, right? Adding global/static variables was
> > adding too much data to BTF or something like that, is that right?
> >
>
> Right. With some experiments, I found the address of a percpu variable
> doesn't necessarily point to a valid structure. So it doesn't make
> sense to dereference runqueues and access its members. However, right
> now there are only percpu variables encoded in BTF, so I can't test
> accessing members of general global/static variables unfortunately.
>
> Hao
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
new file mode 100644
index 000000000000..1dad61ba7e99
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -0,0 +1,77 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Google */
+
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include "test_ksyms_btf.skel.h"
+
+static int duration;
+
+static __u64 kallsyms_find(const char *sym)
+{
+	char type, name[500];
+	__u64 addr, res = 0;
+	FILE *f;
+
+	f = fopen("/proc/kallsyms", "r");
+	if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))
+		return 0;
+
+	while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) {
+		if (strcmp(name, sym) == 0) {
+			res = addr;
+			goto out;
+		}
+	}
+
+	CHECK(false, "not_found", "symbol %s not found\n", sym);
+out:
+	fclose(f);
+	return res;
+}
+
+void test_ksyms_btf(void)
+{
+	__u64 runqueues_addr = kallsyms_find("runqueues");
+	__u64 bpf_prog_active_addr = kallsyms_find("bpf_prog_active");
+	struct test_ksyms_btf *skel;
+	struct test_ksyms_btf__data *data;
+	struct btf *btf;
+	int percpu_datasec;
+	int err;
+
+	btf = libbpf_find_kernel_btf();
+	if (CHECK(IS_ERR(btf), "btf_exists", "failed to load kernel BTF: %ld\n",
+		  PTR_ERR(btf)))
+		return;
+
+	percpu_datasec = btf__find_by_name_kind(btf, ".data..percpu",
+						BTF_KIND_DATASEC);
+	if (percpu_datasec < 0) {
+		printf("%s:SKIP:no PERCPU DATASEC in kernel btf\n",
+		       __func__);
+		test__skip();
+		return;
+	}
+
+	skel = test_ksyms_btf__open_and_load();
+	if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n"))
+		return;
+
+	err = test_ksyms_btf__attach(skel);
+	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+		goto cleanup;
+
+	/* trigger tracepoint */
+	usleep(1);
+
+	data = skel->data;
+	CHECK(data->out__runqueues != runqueues_addr, "runqueues",
+	      "got %llu, exp %llu\n", data->out__runqueues, runqueues_addr);
+	CHECK(data->out__bpf_prog_active != bpf_prog_active_addr, "bpf_prog_active",
+	      "got %llu, exp %llu\n", data->out__bpf_prog_active, bpf_prog_active_addr);
+
+cleanup:
+	test_ksyms_btf__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
new file mode 100644
index 000000000000..e04e31117f84
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
@@ -0,0 +1,23 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Google */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+
+__u64 out__runqueues = -1;
+__u64 out__bpf_prog_active = -1;
+
+extern const struct rq runqueues __ksym; /* struct type global var. */
+extern const int bpf_prog_active __ksym; /* int type global var. */
+
+SEC("raw_tp/sys_enter")
+int handler(const void *ctx)
+{
+	out__runqueues = (__u64)&runqueues;
+	out__bpf_prog_active = (__u64)&bpf_prog_active;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";