ftrace/kallsyms: Have /proc/kallsyms show saved mod init functions

If a module is loaded while tracing is enabled, then there's a possibility
that the module init functions were traced. These functions have their name
and address stored by ftrace such that it can translate the function address
that is written into the buffer into a human readable function name.

As userspace tools may be doing the same, they need a way to map function
names to their address as well. This is done through reading /proc/kallsyms.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 32 insertions, 6 deletions

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 976ecb9..1966fe1 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -479,6 +479,7 @@ EXPORT_SYMBOL(__print_symbol);
 struct kallsym_iter {
 	loff_t pos;
 	loff_t pos_mod_end;
+	loff_t pos_ftrace_mod_end;
 	unsigned long value;
 	unsigned int nameoff; /* If iterating in core kernel symbols. */
 	char type;
@@ -501,11 +502,25 @@ static int get_ksymbol_mod(struct kallsym_iter *iter)
 	return 1;
 }
 
+static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
+{
+	int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
+					 &iter->value, &iter->type,
+					 iter->name, iter->module_name,
+					 &iter->exported);
+	if (ret < 0) {
+		iter->pos_ftrace_mod_end = iter->pos;
+		return 0;
+	}
+
+	return 1;
+}
+
 static int get_ksymbol_bpf(struct kallsym_iter *iter)
 {
 	iter->module_name[0] = '\0';
 	iter->exported = 0;
-	return bpf_get_kallsym(iter->pos - iter->pos_mod_end,
+	return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
 			       &iter->value, &iter->type,
 			       iter->name) < 0 ? 0 : 1;
 }
@@ -530,20 +545,31 @@ static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 	iter->name[0] = '\0';
 	iter->nameoff = get_symbol_offset(new_pos);
 	iter->pos = new_pos;
-	if (new_pos == 0)
+	if (new_pos == 0) {
 		iter->pos_mod_end = 0;
+		iter->pos_ftrace_mod_end = 0;
+	}
 }
 
 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 {
 	iter->pos = pos;
 
-	if (iter->pos_mod_end > 0 &&
-	    iter->pos_mod_end < iter->pos)
+	if (iter->pos_ftrace_mod_end > 0 &&
+	    iter->pos_ftrace_mod_end < iter->pos)
 		return get_ksymbol_bpf(iter);
 
-	if (!get_ksymbol_mod(iter))
-		return get_ksymbol_bpf(iter);
+	if (iter->pos_mod_end > 0 &&
+	    iter->pos_mod_end < iter->pos) {
+		if (!get_ksymbol_ftrace_mod(iter))
+			return get_ksymbol_bpf(iter);
+		return 1;
+	}
+
+	if (!get_ksymbol_mod(iter)) {
+		if (!get_ksymbol_ftrace_mod(iter))
+			return get_ksymbol_bpf(iter);
+	}
 
 	return 1;
 }