user_events: Add print_fmt generation support for basic types

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.

Link: https://lkml.kernel.org/r/20220118204326.2169-3-beaub@linux.microsoft.com
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 77105233115eea5846f5dadeaf09e97b4710a40f..ddc5c3cf1bf86c53a595ca62fb428560e511cb13 100644 (file)
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -359,6 +359,114 @@ 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, const char **str_func)
+{
+       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)
+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, "\"");
+
+       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, &str_func))
+                       pos += snprintf(buf + pos, LEN_OR_ZERO,
+                                       ", %s(%s)", str_func, 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)
@@ -392,6 +500,7 @@ 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 +778,10 @@ 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;