Re: [PATCH v7 13/13] user_events: Use __get_rel_str for relative string fields

Masami Hiramatsu
2021-12-10T01:23:35Z

Hi Beau,

On Thu, 9 Dec 2021 14:32:10 -0800
Beau Belgrave <beaub@linux.microsoft.com> wrote:

> Switch between __get_str and __get_rel_str within the print_fmt of
> user_events. Add unit test to ensure print_fmt is correct on known
> types.
>
> Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
> ---
> kernel/trace/trace_events_user.c | 24 ++-
> .../selftests/user_events/ftrace_test.c | 166 ++++++++++++++++++
> 2 files changed, 182 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 56eb58ddb4cf..3779fa2ca14a 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -257,7 +257,7 @@ static int user_event_add_field(struct user_event *user, const char *type,
> goto add_field;
>
> add_validator:
> - if (strstr(type, "char[") != 0)
> + if (strstr(type, "char") != 0)
> validator_flags |= VALIDATOR_ENSURE_NULL;

What is this change for? This seems not related to the other changes.
(Also, what happen if it is a single char type?)

>
> validator = kmalloc(sizeof(*validator), GFP_KERNEL);
> @@ -456,14 +456,21 @@ static const char *user_field_format(const char *type)
> return "%llu";
> }
>
> -static bool user_field_is_dyn_string(const char *type)
> +static bool user_field_is_dyn_string(const char *type, const char **str_func)
> {
> - if (str_has_prefix(type, "__data_loc ") ||
> - str_has_prefix(type, "__rel_loc "))
> - if (strstr(type, "char[") != 0)
> - return true;
> + if (str_has_prefix(type, "__data_loc ")) {
> + *str_func = "__get_str";
> + goto check;
> + }
> +
> + if (str_has_prefix(type, "__rel_loc ")) {
> + *str_func = "__get_rel_str";
> + goto check;
> + }
>
> return false;
> +check:
> + return strstr(type, "char") != 0;
> }
>
> #define LEN_OR_ZERO (len ? len - pos : 0)
> @@ -472,6 +479,7 @@ static int user_event_set_print_fmt(struct user_event *user, char *buf, int len)
> struct ftrace_event_field *field, *next;
> struct list_head *head = &user->fields;
> int pos = 0, depth = 0;
> + const char *str_func;
>
> pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
>
> @@ -488,9 +496,9 @@ static int user_event_set_print_fmt(struct user_event *user, char *buf, int len)
> pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
>
> list_for_each_entry_safe_reverse(field, next, head, link) {
> - if (user_field_is_dyn_string(field->type))
> + if (user_field_is_dyn_string(field->type, &str_func))
> pos += snprintf(buf + pos, LEN_OR_ZERO,
> - ", __get_str(%s)", field->name);
> + ", %s(%s)", str_func, field->name);
> else
> pos += snprintf(buf + pos, LEN_OR_ZERO,
> ", REC->%s", field->name);
> diff --git a/tools/testing/selftests/user_events/ftrace_test.c b/tools/testing/selftests/user_events/ftrace_test.c

Just a nitpick, if possible, please split this part from the kernel update.

> index 16aff1fb295a..b2e5c0765a68 100644
> --- a/tools/testing/selftests/user_events/ftrace_test.c
> +++ b/tools/testing/selftests/user_events/ftrace_test.c
> @@ -20,6 +20,7 @@ const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
> const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
> const char *enable_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/enable";
> const char *trace_file = "/sys/kernel/debug/tracing/trace";
> +const char *fmt_file = "/sys/kernel/debug/tracing/events/user_events/__test_event/format";
>
> static int trace_bytes(void)
> {
> @@ -47,6 +48,61 @@ static int trace_bytes(void)
> return bytes;
> }
>
> +static int get_print_fmt(char *buffer, int len)
> +{
> + FILE *fp = fopen(fmt_file, "r");
> + int c, index = 0, last = 0;
> +
> + if (!fp)
> + return -1;
> +
> + /* Read until empty line (Skip Common) */
> + while (true) {
> + c = getc(fp);
> +
> + if (c == EOF)
> + break;
> +
> + if (last == '\n' && c == '\n')
> + break;
> +
> + last = c;
> + }

Another nitpick, maybe you need a function like skip_until_empty_line(fp)
and repeat it like this.

if (skip_until_empty_line(fp) < 0)
goto out;
if (skip_until_empty_line(fp) < 0)
goto out;

> +
> + last = 0;
> +
> + /* Read until empty line (Skip Properties) */
> + while (true) {
> + c = getc(fp);
> +
> + if (c == EOF)
> + break;
> +
> + if (last == '\n' && c == '\n')
> + break;
> +
> + last = c;
> + }
> +
> + /* Read in print_fmt: */
> + while (len > 1) {
> + c = getc(fp);
> +
> + if (c == EOF || c == '\n')
> + break;
> +
> + buffer[index++] = c;
> +
> + len--;
> + }

And here you can use fgets(buffer, len, fp).

Thank you,

> +
> + buffer[index] = 0;
> +
> + fclose(fp);
> +
> + return 0;
> +}
> +
> static int clear(void)
> {
> int fd = open(data_file, O_RDWR);
> @@ -63,6 +119,44 @@ static int clear(void)
> return 0;
> }
>
> +static int check_print_fmt(const char *event, const char *expected)
> +{
> + struct user_reg reg = {0};
> + char print_fmt[256];
> + int ret;
> + int fd;
> +
> + /* Ensure cleared */
> + ret = clear();
> +
> + if (ret != 0)
> + return ret;
> +
> + fd = open(data_file, O_RDWR);
> +
> + if (fd == -1)
> + return fd;
> +
> + reg.size = sizeof(reg);
> + reg.name_args = (__u64)event;
> +
> + /* Register should work */
> + ret = ioctl(fd, DIAG_IOCSREG, &reg);
> +
> + close(fd);
> +
> + if (ret != 0)
> + return ret;
> +
> + /* Ensure correct print_fmt */
> + ret = get_print_fmt(print_fmt, sizeof(print_fmt));
> +
> + if (ret != 0)
> + return ret;
> +
> + return strcmp(print_fmt, expected);
> +}
> +
> FIXTURE(user) {
> int status_fd;
> int data_fd;
> @@ -282,6 +376,78 @@ TEST_F(user, write_validator) {
> ASSERT_EQ(EFAULT, errno);
> }
>
> +TEST_F(user, print_fmt) {
> + int ret;
> +
> + ret = check_print_fmt("__test_event __rel_loc char[] data",
> + "print fmt: \"data=%s\", __get_rel_str(data)");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event __data_loc char[] data",
> + "print fmt: \"data=%s\", __get_str(data)");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event s64 data",
> + "print fmt: \"data=%lld\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event u64 data",
> + "print fmt: \"data=%llu\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event s32 data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event u32 data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event int data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event unsigned int data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event s16 data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event u16 data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event short data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event unsigned short data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event s8 data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event u8 data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event char data",
> + "print fmt: \"data=%d\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event unsigned char data",
> + "print fmt: \"data=%u\", REC->data");
> + ASSERT_EQ(0, ret);
> +
> + ret = check_print_fmt("__test_event char[4] data",
> + "print fmt: \"data=%s\", REC->data");
> + ASSERT_EQ(0, ret);
> +}
> +
> int main(int argc, char **argv)
> {
> return test_harness_run(argc, argv);
> --
> 2.17.1
>

--
Masami Hiramatsu <mhiramat@kernel.org>