Commit 8261ef2e authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing: Add BUILD_BUG() to make sure stacktrace fits in strings 

The max string length for a histogram variable is 256 bytes. The max depth
of a stacktrace is 16. With 8byte words, that's 16 * 8 = 128. Which can
easily fit in the string variable. The histogram stacktrace is being
stored in the string value (with the given max length), with the
assumption it will fit. To make sure that this is always the case (in the
case that the stack trace depth increases), add a BUILD_BUG_ON() to test
this.

Link: https://lore.kernel.org/linux-trace-kernel/20230214002418.0103b9e765d3e5c374d2aa7d@kernel.org/



Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent fc1a9dc1

kernel/trace/trace_events_hist.c

+3 −0
Original line number Diff line number Diff line
@@ -3119,6 +3119,9 @@ static inline void __update_field_vars(struct tracing_map_elt *elt, 
	unsigned int i, j, var_idx;

	u64 var_val;



	/* Make sure stacktrace can fit in the string variable length */

	BUILD_BUG_ON((HIST_STACKTRACE_DEPTH + 1) * sizeof(long) >= STR_VAR_LEN_MAX);



	for (i = 0, j = field_var_str_start; i < n_field_vars; i++) {

		struct field_var *field_var = field_vars[i];

		struct hist_field *var = field_var->var;