diff mbox series

[2/2] selftest/bpf: Test returning zero from a perf bpf program suppresses SIGIO.

Message ID 20231204201406.341074-3-khuey@kylehuey.com
State New
Headers
Series Combine perf and bpf for fast eval of hw breakpoint conditions |

Commit Message

Kyle Huey Dec. 4, 2023, 8:14 p.m. UTC 
  The test sets a hardware breakpoint and uses a bpf program to suppress the
I/O availability signal if the ip matches the expected value.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
 .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
 2 files changed, 118 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c

Comments

Andrii Nakryiko Dec. 4, 2023, 10:14 p.m. UTC | #1 
On Mon, Dec 4, 2023 at 12:14 PM Kyle Huey <me@kylehuey.com> wrote:
>
> The test sets a hardware breakpoint and uses a bpf program to suppress the
> I/O availability signal if the ip matches the expected value.
>
> Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> ---
>  .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
>  .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
>  2 files changed, 118 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> new file mode 100644
> index 000000000000..b269a31669b7
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include "test_perf_skip.skel.h"
> +#include <linux/hw_breakpoint.h>
> +#include <sys/mman.h>
> +
> +#define BPF_OBJECT            "test_perf_skip.bpf.o"

leftover?

> +
> +static void handle_sig(int)
> +{
> +       ASSERT_OK(1, "perf event not skipped");
> +}
> +
> +static noinline int test_function(void)
> +{

please add

asm volatile ("");

here to prevent compiler from actually inlining at the call site

> +       return 0;
> +}
> +
> +void serial_test_perf_skip(void)
> +{
> +       sighandler_t previous;
> +       int duration = 0;
> +       struct test_perf_skip *skel = NULL;
> +       int map_fd = -1;
> +       long page_size = sysconf(_SC_PAGE_SIZE);
> +       uintptr_t *ip = NULL;
> +       int prog_fd = -1;
> +       struct perf_event_attr attr = {0};
> +       int perf_fd = -1;
> +       struct f_owner_ex owner;
> +       int err;
> +
> +       previous = signal(SIGIO, handle_sig);
> +
> +       skel = test_perf_skip__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "skel_load"))
> +               goto cleanup;
> +
> +       prog_fd = bpf_program__fd(skel->progs.handler);
> +       if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
> +               goto cleanup;
> +
> +       map_fd = bpf_map__fd(skel->maps.ip);
> +       if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
> +               goto cleanup;
> +
> +       ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
> +       if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
> +               goto cleanup;
> +
> +       *ip = (uintptr_t)test_function;
> +
> +       attr.type = PERF_TYPE_BREAKPOINT;
> +       attr.size = sizeof(attr);
> +       attr.bp_type = HW_BREAKPOINT_X;
> +       attr.bp_addr = (uintptr_t)test_function;
> +       attr.bp_len = sizeof(long);
> +       attr.sample_period = 1;
> +       attr.sample_type = PERF_SAMPLE_IP;
> +       attr.pinned = 1;
> +       attr.exclude_kernel = 1;
> +       attr.exclude_hv = 1;
> +       attr.precise_ip = 3;
> +
> +       perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
> +       if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))

please don't use CHECK() macro, stick to ASSERT_xxx()

also, we are going to run all this on different hardware and VMs, see
how we skip tests if hardware support is not there. See test__skip
usage in prog_tests/perf_branches.c, as one example

> +               goto cleanup;
> +
> +       err = fcntl(perf_fd, F_SETFL, O_ASYNC);

I assume this is what will send SIGIO, right? Can you add a small
comment explicitly saying this?

> +       if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
> +               goto cleanup;
> +
> +       owner.type = F_OWNER_TID;
> +       owner.pid = gettid();
> +       err = fcntl(perf_fd, F_SETOWN_EX, &owner);
> +       if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
> +               goto cleanup;
> +
> +       err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> +       if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
> +               goto cleanup;

we have a better way to do this, please use
bpf_program__attach_perf_event() instead

> +
> +       test_function();
> +
> +cleanup:
> +       if (perf_fd >= 0)
> +               close(perf_fd);
> +       if (ip)
> +               munmap(ip, page_size);
> +       if (skel)
> +               test_perf_skip__destroy(skel);
> +
> +       signal(SIGIO, previous);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> new file mode 100644
> index 000000000000..ef01a9161afe
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_ARRAY);
> +       __uint(max_entries, 1);
> +       __uint(map_flags, BPF_F_MMAPABLE);
> +       __type(key, uint32_t);
> +       __type(value, uintptr_t);
> +} ip SEC(".maps");

please use global variable:

__u64 ip;

and then access it from user-space side through skeleton

skel->bss.ip = &test_function;

> +
> +SEC("perf_event")
> +int handler(struct bpf_perf_event_data *data)
> +{
> +       const uint32_t index = 0;
> +       uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
> +
> +       return !(v && *v == PT_REGS_IP(&data->regs));

and so we the above global var suggestion this will be just:

return ip == PT_REGS_IP(&data->regs);

> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.34.1
>
Jiri Olsa Dec. 5, 2023, 11:17 a.m. UTC | #2 
On Mon, Dec 04, 2023 at 12:14:06PM -0800, Kyle Huey wrote:
> The test sets a hardware breakpoint and uses a bpf program to suppress the
> I/O availability signal if the ip matches the expected value.
> 
> Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> ---
>  .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
>  .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
>  2 files changed, 118 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> new file mode 100644
> index 000000000000..b269a31669b7
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include "test_perf_skip.skel.h"
> +#include <linux/hw_breakpoint.h>
> +#include <sys/mman.h>
> +
> +#define BPF_OBJECT            "test_perf_skip.bpf.o"
> +
> +static void handle_sig(int)
> +{
> +	ASSERT_OK(1, "perf event not skipped");
> +}
> +
> +static noinline int test_function(void)
> +{
> +	return 0;
> +}
> +
> +void serial_test_perf_skip(void)

does it need to be serial?

jirka
Yonghong Song Dec. 5, 2023, 4:54 p.m. UTC | #3 
On 12/4/23 3:14 PM, Kyle Huey wrote:
> The test sets a hardware breakpoint and uses a bpf program to suppress the
> I/O availability signal if the ip matches the expected value.
>
> Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> ---
>   .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
>   .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
>   2 files changed, 118 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> new file mode 100644
> index 000000000000..b269a31669b7
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include "test_perf_skip.skel.h"
> +#include <linux/hw_breakpoint.h>
> +#include <sys/mman.h>
> +
> +#define BPF_OBJECT            "test_perf_skip.bpf.o"
> +
> +static void handle_sig(int)

I hit a warning here:
home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:10:27: error: omitting the parameter name in a function definition is a C23 extension [-Werror,-Wc23-extensions]
    10 | static void handle_sig(int)
       |

Add a parameter and marked as unused can resolve the issue.

#define __always_unused         __attribute__((__unused__))

static void handle_sig(int unused __always_unused)
{
         ASSERT_OK(1, "perf event not skipped");
}


> +{
> +	ASSERT_OK(1, "perf event not skipped");
> +}
> +
> +static noinline int test_function(void)
> +{
> +	return 0;
> +}
> +
> +void serial_test_perf_skip(void)
> +{
> +	sighandler_t previous;
> +	int duration = 0;
> +	struct test_perf_skip *skel = NULL;
> +	int map_fd = -1;
> +	long page_size = sysconf(_SC_PAGE_SIZE);
> +	uintptr_t *ip = NULL;
> +	int prog_fd = -1;
> +	struct perf_event_attr attr = {0};
> +	int perf_fd = -1;
> +	struct f_owner_ex owner;
> +	int err;
> +
> +	previous = signal(SIGIO, handle_sig);
> +
> +	skel = test_perf_skip__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_load"))
> +		goto cleanup;
> +
> +	prog_fd = bpf_program__fd(skel->progs.handler);
> +	if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
> +		goto cleanup;
> +
> +	map_fd = bpf_map__fd(skel->maps.ip);
> +	if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
> +		goto cleanup;
> +
> +	ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
> +	if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
> +		goto cleanup;
> +
> +	*ip = (uintptr_t)test_function;
> +
> +	attr.type = PERF_TYPE_BREAKPOINT;
> +	attr.size = sizeof(attr);
> +	attr.bp_type = HW_BREAKPOINT_X;
> +	attr.bp_addr = (uintptr_t)test_function;
> +	attr.bp_len = sizeof(long);
> +	attr.sample_period = 1;
> +	attr.sample_type = PERF_SAMPLE_IP;
> +	attr.pinned = 1;
> +	attr.exclude_kernel = 1;
> +	attr.exclude_hv = 1;
> +	attr.precise_ip = 3;
> +
> +	perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
> +	if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))
> +		goto cleanup;
> +
> +	err = fcntl(perf_fd, F_SETFL, O_ASYNC);
> +	if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
> +		goto cleanup;
> +
> +	owner.type = F_OWNER_TID;
> +	owner.pid = gettid();

I hit a compilation failure here:

/home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:75:14: error: call to undeclared function 'gettid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    75 |         owner.pid = gettid();
       |                     ^

If you looked at some other examples, the common usage is do 'syscall(SYS_gettid)'.
So the following patch should fix the compilation error:

#include <sys/syscall.h>
...
         owner.pid = syscall(SYS_gettid);
...

> +	err = fcntl(perf_fd, F_SETOWN_EX, &owner);
> +	if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
> +		goto cleanup;
> +
> +	err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> +	if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
> +		goto cleanup;
> +
> +	test_function();

As Andrii has mentioned in previous comments, we will have
issue is RELEASE version of selftest is built
   RELEASE=1 make ...

See https://lore.kernel.org/bpf/20231127050342.1945270-1-yonghong.song@linux.dev

> +
> +cleanup:
> +	if (perf_fd >= 0)
> +		close(perf_fd);
> +	if (ip)
> +		munmap(ip, page_size);
> +	if (skel)
> +		test_perf_skip__destroy(skel);
> +
> +	signal(SIGIO, previous);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> new file mode 100644
> index 000000000000..ef01a9161afe
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_ARRAY);
> +	__uint(max_entries, 1);
> +	__uint(map_flags, BPF_F_MMAPABLE);
> +	__type(key, uint32_t);
> +	__type(value, uintptr_t);
> +} ip SEC(".maps");
> +
> +SEC("perf_event")
> +int handler(struct bpf_perf_event_data *data)
> +{
> +	const uint32_t index = 0;
> +	uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
> +
> +	return !(v && *v == PT_REGS_IP(&data->regs));
> +}
> +
> +char _license[] SEC("license") = "GPL";
Kyle Huey Dec. 5, 2023, 5:52 p.m. UTC | #4 
On Tue, Dec 5, 2023 at 8:54 AM Yonghong Song <yonghong.song@linux.dev> wrote:
>
>
> On 12/4/23 3:14 PM, Kyle Huey wrote:
> > The test sets a hardware breakpoint and uses a bpf program to suppress the
> > I/O availability signal if the ip matches the expected value.
> >
> > Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> > ---
> >   .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
> >   .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
> >   2 files changed, 118 insertions(+)
> >   create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
> >   create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > new file mode 100644
> > index 000000000000..b269a31669b7
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > @@ -0,0 +1,95 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define _GNU_SOURCE
> > +#include <test_progs.h>
> > +#include "test_perf_skip.skel.h"
> > +#include <linux/hw_breakpoint.h>
> > +#include <sys/mman.h>
> > +
> > +#define BPF_OBJECT            "test_perf_skip.bpf.o"
> > +
> > +static void handle_sig(int)
>
> I hit a warning here:
> home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:10:27: error: omitting the parameter name in a function definition is a C23 extension [-Werror,-Wc23-extensions]

Yeah, Meta's kernel-ci bot sent me off-list email about this one.

>
>     10 | static void handle_sig(int)
>        |
>
> Add a parameter and marked as unused can resolve the issue.
>
> #define __always_unused         __attribute__((__unused__))
>
> static void handle_sig(int unused __always_unused)
> {
>          ASSERT_OK(1, "perf event not skipped");
> }
>
>
> > +{
> > +     ASSERT_OK(1, "perf event not skipped");
> > +}
> > +
> > +static noinline int test_function(void)
> > +{
> > +     return 0;
> > +}
> > +
> > +void serial_test_perf_skip(void)
> > +{
> > +     sighandler_t previous;
> > +     int duration = 0;
> > +     struct test_perf_skip *skel = NULL;
> > +     int map_fd = -1;
> > +     long page_size = sysconf(_SC_PAGE_SIZE);
> > +     uintptr_t *ip = NULL;
> > +     int prog_fd = -1;
> > +     struct perf_event_attr attr = {0};
> > +     int perf_fd = -1;
> > +     struct f_owner_ex owner;
> > +     int err;
> > +
> > +     previous = signal(SIGIO, handle_sig);
> > +
> > +     skel = test_perf_skip__open_and_load();
> > +     if (!ASSERT_OK_PTR(skel, "skel_load"))
> > +             goto cleanup;
> > +
> > +     prog_fd = bpf_program__fd(skel->progs.handler);
> > +     if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
> > +             goto cleanup;
> > +
> > +     map_fd = bpf_map__fd(skel->maps.ip);
> > +     if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
> > +             goto cleanup;
> > +
> > +     ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
> > +     if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
> > +             goto cleanup;
> > +
> > +     *ip = (uintptr_t)test_function;
> > +
> > +     attr.type = PERF_TYPE_BREAKPOINT;
> > +     attr.size = sizeof(attr);
> > +     attr.bp_type = HW_BREAKPOINT_X;
> > +     attr.bp_addr = (uintptr_t)test_function;
> > +     attr.bp_len = sizeof(long);
> > +     attr.sample_period = 1;
> > +     attr.sample_type = PERF_SAMPLE_IP;
> > +     attr.pinned = 1;
> > +     attr.exclude_kernel = 1;
> > +     attr.exclude_hv = 1;
> > +     attr.precise_ip = 3;
> > +
> > +     perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
> > +     if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))
> > +             goto cleanup;
> > +
> > +     err = fcntl(perf_fd, F_SETFL, O_ASYNC);
> > +     if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
> > +             goto cleanup;
> > +
> > +     owner.type = F_OWNER_TID;
> > +     owner.pid = gettid();
>
> I hit a compilation failure here:
>
> /home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:75:14: error: call to undeclared function 'gettid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     75 |         owner.pid = gettid();
>        |                     ^
>
> If you looked at some other examples, the common usage is do 'syscall(SYS_gettid)'.

Not clear why this works for me but sure I'll change that.

>
> So the following patch should fix the compilation error:
>
> #include <sys/syscall.h>
> ...
>          owner.pid = syscall(SYS_gettid);
> ...
>
> > +     err = fcntl(perf_fd, F_SETOWN_EX, &owner);
> > +     if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
> > +             goto cleanup;
> > +
> > +     err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> > +     if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
> > +             goto cleanup;
> > +
> > +     test_function();
>
> As Andrii has mentioned in previous comments, we will have
> issue is RELEASE version of selftest is built
>    RELEASE=1 make ...
>
> See https://lore.kernel.org/bpf/20231127050342.1945270-1-yonghong.song@linux.dev

Not sure I follow this one. Are you saying adding asm volatile ("") in
test_function() is *not* sufficient?

- Kyle

>
> > +
> > +cleanup:
> > +     if (perf_fd >= 0)
> > +             close(perf_fd);
> > +     if (ip)
> > +             munmap(ip, page_size);
> > +     if (skel)
> > +             test_perf_skip__destroy(skel);
> > +
> > +     signal(SIGIO, previous);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> > new file mode 100644
> > index 000000000000..ef01a9161afe
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> > @@ -0,0 +1,23 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include "vmlinux.h"
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +
> > +struct {
> > +     __uint(type, BPF_MAP_TYPE_ARRAY);
> > +     __uint(max_entries, 1);
> > +     __uint(map_flags, BPF_F_MMAPABLE);
> > +     __type(key, uint32_t);
> > +     __type(value, uintptr_t);
> > +} ip SEC(".maps");
> > +
> > +SEC("perf_event")
> > +int handler(struct bpf_perf_event_data *data)
> > +{
> > +     const uint32_t index = 0;
> > +     uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
> > +
> > +     return !(v && *v == PT_REGS_IP(&data->regs));
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
Kyle Huey Dec. 5, 2023, 6:21 p.m. UTC | #5 
On Mon, Dec 4, 2023 at 2:14 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Dec 4, 2023 at 12:14 PM Kyle Huey <me@kylehuey.com> wrote:
> >
> > The test sets a hardware breakpoint and uses a bpf program to suppress the
> > I/O availability signal if the ip matches the expected value.
> >
> > Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> > ---
> >  .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
> >  .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
> >  2 files changed, 118 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > new file mode 100644
> > index 000000000000..b269a31669b7
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
> > @@ -0,0 +1,95 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#define _GNU_SOURCE
> > +#include <test_progs.h>
> > +#include "test_perf_skip.skel.h"
> > +#include <linux/hw_breakpoint.h>
> > +#include <sys/mman.h>
> > +
> > +#define BPF_OBJECT            "test_perf_skip.bpf.o"
>
> leftover?

Indeed. Fixed.

> > +
> > +static void handle_sig(int)
> > +{
> > +       ASSERT_OK(1, "perf event not skipped");
> > +}
> > +
> > +static noinline int test_function(void)
> > +{
>
> please add
>
> asm volatile ("");
>
> here to prevent compiler from actually inlining at the call site

Ok.

> > +       return 0;
> > +}
> > +
> > +void serial_test_perf_skip(void)
> > +{
> > +       sighandler_t previous;
> > +       int duration = 0;
> > +       struct test_perf_skip *skel = NULL;
> > +       int map_fd = -1;
> > +       long page_size = sysconf(_SC_PAGE_SIZE);
> > +       uintptr_t *ip = NULL;
> > +       int prog_fd = -1;
> > +       struct perf_event_attr attr = {0};
> > +       int perf_fd = -1;
> > +       struct f_owner_ex owner;
> > +       int err;
> > +
> > +       previous = signal(SIGIO, handle_sig);
> > +
> > +       skel = test_perf_skip__open_and_load();
> > +       if (!ASSERT_OK_PTR(skel, "skel_load"))
> > +               goto cleanup;
> > +
> > +       prog_fd = bpf_program__fd(skel->progs.handler);
> > +       if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
> > +               goto cleanup;
> > +
> > +       map_fd = bpf_map__fd(skel->maps.ip);
> > +       if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
> > +               goto cleanup;
> > +
> > +       ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
> > +       if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
> > +               goto cleanup;
> > +
> > +       *ip = (uintptr_t)test_function;
> > +
> > +       attr.type = PERF_TYPE_BREAKPOINT;
> > +       attr.size = sizeof(attr);
> > +       attr.bp_type = HW_BREAKPOINT_X;
> > +       attr.bp_addr = (uintptr_t)test_function;
> > +       attr.bp_len = sizeof(long);
> > +       attr.sample_period = 1;
> > +       attr.sample_type = PERF_SAMPLE_IP;
> > +       attr.pinned = 1;
> > +       attr.exclude_kernel = 1;
> > +       attr.exclude_hv = 1;
> > +       attr.precise_ip = 3;
> > +
> > +       perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
> > +       if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))
>
> please don't use CHECK() macro, stick to ASSERT_xxx()

Done.

> also, we are going to run all this on different hardware and VMs, see
> how we skip tests if hardware support is not there. See test__skip
> usage in prog_tests/perf_branches.c, as one example

Hmm I suppose it should be conditioned on CONFIG_HAVE_HW_BREAKPOINT.

> > +               goto cleanup;
> > +
> > +       err = fcntl(perf_fd, F_SETFL, O_ASYNC);
>
> I assume this is what will send SIGIO, right? Can you add a small
> comment explicitly saying this?

Done.

> > +       if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
> > +               goto cleanup;
> > +
> > +       owner.type = F_OWNER_TID;
> > +       owner.pid = gettid();
> > +       err = fcntl(perf_fd, F_SETOWN_EX, &owner);
> > +       if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
> > +               goto cleanup;
> > +
> > +       err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> > +       if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
> > +               goto cleanup;
>
> we have a better way to do this, please use
> bpf_program__attach_perf_event() instead

Done.

> > +
> > +       test_function();
> > +
> > +cleanup:
> > +       if (perf_fd >= 0)
> > +               close(perf_fd);
> > +       if (ip)
> > +               munmap(ip, page_size);
> > +       if (skel)
> > +               test_perf_skip__destroy(skel);
> > +
> > +       signal(SIGIO, previous);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> > new file mode 100644
> > index 000000000000..ef01a9161afe
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
> > @@ -0,0 +1,23 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include "vmlinux.h"
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +
> > +struct {
> > +       __uint(type, BPF_MAP_TYPE_ARRAY);
> > +       __uint(max_entries, 1);
> > +       __uint(map_flags, BPF_F_MMAPABLE);
> > +       __type(key, uint32_t);
> > +       __type(value, uintptr_t);
> > +} ip SEC(".maps");
>
> please use global variable:
>
> __u64 ip;
>
> and then access it from user-space side through skeleton
>
> skel->bss.ip = &test_function;

Done.

> > +
> > +SEC("perf_event")
> > +int handler(struct bpf_perf_event_data *data)
> > +{
> > +       const uint32_t index = 0;
> > +       uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
> > +
> > +       return !(v && *v == PT_REGS_IP(&data->regs));
>
> and so we the above global var suggestion this will be just:
>
> return ip == PT_REGS_IP(&data->regs);
>
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > --
> > 2.34.1
> >

- Kyle
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
new file mode 100644
index 000000000000..b269a31669b7
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
@@ -0,0 +1,95 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <test_progs.h>
+#include "test_perf_skip.skel.h"
+#include <linux/hw_breakpoint.h>
+#include <sys/mman.h>
+
+#define BPF_OBJECT            "test_perf_skip.bpf.o"
+
+static void handle_sig(int)
+{
+	ASSERT_OK(1, "perf event not skipped");
+}
+
+static noinline int test_function(void)
+{
+	return 0;
+}
+
+void serial_test_perf_skip(void)
+{
+	sighandler_t previous;
+	int duration = 0;
+	struct test_perf_skip *skel = NULL;
+	int map_fd = -1;
+	long page_size = sysconf(_SC_PAGE_SIZE);
+	uintptr_t *ip = NULL;
+	int prog_fd = -1;
+	struct perf_event_attr attr = {0};
+	int perf_fd = -1;
+	struct f_owner_ex owner;
+	int err;
+
+	previous = signal(SIGIO, handle_sig);
+
+	skel = test_perf_skip__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.handler);
+	if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
+		goto cleanup;
+
+	map_fd = bpf_map__fd(skel->maps.ip);
+	if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
+		goto cleanup;
+
+	ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
+	if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
+		goto cleanup;
+
+	*ip = (uintptr_t)test_function;
+
+	attr.type = PERF_TYPE_BREAKPOINT;
+	attr.size = sizeof(attr);
+	attr.bp_type = HW_BREAKPOINT_X;
+	attr.bp_addr = (uintptr_t)test_function;
+	attr.bp_len = sizeof(long);
+	attr.sample_period = 1;
+	attr.sample_type = PERF_SAMPLE_IP;
+	attr.pinned = 1;
+	attr.exclude_kernel = 1;
+	attr.exclude_hv = 1;
+	attr.precise_ip = 3;
+
+	perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
+	if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))
+		goto cleanup;
+
+	err = fcntl(perf_fd, F_SETFL, O_ASYNC);
+	if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
+		goto cleanup;
+
+	owner.type = F_OWNER_TID;
+	owner.pid = gettid();
+	err = fcntl(perf_fd, F_SETOWN_EX, &owner);
+	if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
+		goto cleanup;
+
+	err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
+	if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
+		goto cleanup;
+
+	test_function();
+
+cleanup:
+	if (perf_fd >= 0)
+		close(perf_fd);
+	if (ip)
+		munmap(ip, page_size);
+	if (skel)
+		test_perf_skip__destroy(skel);
+
+	signal(SIGIO, previous);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
new file mode 100644
index 000000000000..ef01a9161afe
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
@@ -0,0 +1,23 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__uint(map_flags, BPF_F_MMAPABLE);
+	__type(key, uint32_t);
+	__type(value, uintptr_t);
+} ip SEC(".maps");
+
+SEC("perf_event")
+int handler(struct bpf_perf_event_data *data)
+{
+	const uint32_t index = 0;
+	uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
+
+	return !(v && *v == PT_REGS_IP(&data->regs));
+}
+
+char _license[] SEC("license") = "GPL";