perf symbols: Add documentation to 'struct symbol'

Refactor some existing comments and then infer the rest.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin Liška <mliska@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211112035124.94327-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.h

@@ -40,22 +40,33 @@ Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
 			     GElf_Shdr *shp, const char *name, size_t *idx);
 #endif
 
-/** struct symbol - symtab entry
- *
- * @ignore - resolvable but tools ignore it (e.g. idle routines)
+/**
+ * A symtab entry. When allocated this may be preceded by an annotation (see
+ * symbol__annotation), a browser_index (see symbol__browser_index) and rb_node
+ * to sort by name (see struct symbol_name_rb_node).
  */
 struct symbol {
 	struct rb_node	rb_node;
+	/** Range of symbol [start, end). */
 	u64		start;
 	u64		end;
+	/** Length of the string name. */
 	u16		namelen;
+	/** ELF symbol type as defined for st_info. E.g STT_OBJECT or STT_FUNC. */
 	u8		type:4;
+	/** ELF binding type as defined for st_info. E.g. STB_WEAK or STB_GLOBAL. */
 	u8		binding:4;
+	/** Set true for kernel symbols of idle routines. */
 	u8		idle:1;
+	/** Resolvable but tools ignore it (e.g. idle routines). */
 	u8		ignore:1;
+	/** Symbol for an inlined function. */
 	u8		inlined:1;
+	/** Architecture specific. Unused except on PPC where it holds st_other. */
 	u8		arch_sym;
+	/** Has symbol__annotate2 been performed. */
 	bool		annotate2;
+	/** The name of length namelen associated with the symbol. */
 	char		name[];
 };