[PATCH v6 03/13] user_events: Add print_fmt generation support for basic types

Beau Belgrave
2021-12-01T18:25:42Z

Addes print_fmt format generation for basic types that are supported for
user processes. Only supports sizes that are the same on 32 and 64 bit.

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
kernel/trace/trace_events_user.c | 107 ++++++++++++++++++++++++++++++-
1 file changed, 105 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index afcf224b941d..ad8e0e359eab 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -357,6 +357,106 @@ static int user_event_parse_fields(struct user_event *user, char *args)

static struct trace_event_fields user_event_fields_array[1];

+static const char *user_field_format(const char *type)
+{
+ if (strcmp(type, "s64") == 0)
+ return "%lld";
+ if (strcmp(type, "u64") == 0)
+ return "%llu";
+ if (strcmp(type, "s32") == 0)
+ return "%d";
+ if (strcmp(type, "u32") == 0)
+ return "%u";
+ if (strcmp(type, "int") == 0)
+ return "%d";
+ if (strcmp(type, "unsigned int") == 0)
+ return "%u";
+ if (strcmp(type, "s16") == 0)
+ return "%d";
+ if (strcmp(type, "u16") == 0)
+ return "%u";
+ if (strcmp(type, "short") == 0)
+ return "%d";
+ if (strcmp(type, "unsigned short") == 0)
+ return "%u";
+ if (strcmp(type, "s8") == 0)
+ return "%d";
+ if (strcmp(type, "u8") == 0)
+ return "%u";
+ if (strcmp(type, "char") == 0)
+ return "%d";
+ if (strcmp(type, "unsigned char") == 0)
+ return "%u";
+ if (strstr(type, "char[") != 0)
+ return "%s";
+
+ /* Unknown, likely struct, allowed treat as 64-bit */
+ return "%llu";
+}
+
+static bool user_field_is_dyn_string(const char *type)
+{
+ if (str_has_prefix(type, "__data_loc ") ||
+ str_has_prefix(type, "__rel_loc "))
+ if (strstr(type, "char[") != 0)
+ return true;
+
+ return false;
+}
+
+#define LEN_OR_ZERO (len ? len - pos : 0)
+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;
+
+ pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
+
+ list_for_each_entry_safe_reverse(field, next, head, link) {
+ if (depth != 0)
+ pos += snprintf(buf + pos, LEN_OR_ZERO, " ");
+
+ pos += snprintf(buf + pos, LEN_OR_ZERO, "%s=%s",
+ field->name, user_field_format(field->type));
+
+ depth++;
+ }
+
+ 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))
+ pos += snprintf(buf + pos, LEN_OR_ZERO,
+ ", __get_str(%s)", field->name);
+ else
+ pos += snprintf(buf + pos, LEN_OR_ZERO,
+ ", REC->%s", field->name);
+ }
+
+ return pos + 1;
+}
+#undef LEN_OR_ZERO
+
+static int user_event_create_print_fmt(struct user_event *user)
+{
+ char *print_fmt;
+ int len;
+
+ len = user_event_set_print_fmt(user, NULL, 0);
+
+ print_fmt = kmalloc(len, GFP_KERNEL);
+
+ if (!print_fmt)
+ return -ENOMEM;
+
+ user_event_set_print_fmt(user, print_fmt, len);
+
+ user->call.print_fmt = print_fmt;
+
+ return 0;
+}
+
static enum print_line_t user_event_print_trace(struct trace_iterator *iter,
int flags,
struct trace_event *event)
@@ -390,6 +490,7 @@ static int destroy_user_event(struct user_event *user)
clear_bit(user->index, page_bitmap);
hash_del(&user->node);

+ kfree(user->call.print_fmt);
kfree(EVENT_NAME(user));
kfree(user);

@@ -669,8 +770,10 @@ static int user_event_parse(char *name, char *args, char *flags,
if (ret)
goto put_user;

- /* Minimal print format */
- user->call.print_fmt = "\"\"";
+ ret = user_event_create_print_fmt(user);
+
+ if (ret)
+ goto put_user;

user->call.data = user;
user->call.class = &user->class;
--
2.17.1