From 915f64901eb3f1e4e126f58c0d2f82f5ec1d1223 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <yamada.masahiro@socionext.com>
Date: Mon, 28 May 2018 18:21:55 +0900
Subject: [PATCH] kconfig: error out if a recursive variable references itself
When using a recursively expanded variable, it is a common mistake
to make circular reference.
For example, Make terminates the following code:
X = $(X)
Y := $(X)
Let's detect the circular expansion in Kconfig, too.
On the other hand, a function that recurses itself is a commonly-used
programming technique. So, Make does not check recursion in the
reference with 'call'. For example, the following code continues
running eternally:
X = $(call X)
Y := $(X)
Kconfig allows circular expansion if one or more arguments are given,
but terminates when the same function is recursively invoked 1000 times,
assuming it is a programming mistake.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
scripts/kconfig/preprocess.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index 0574039238c65..65da87fce907a 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -229,6 +229,7 @@ struct variable {
char *name;
char *value;
enum variable_flavor flavor;
+ int exp_count;
struct list_head node;
};
@@ -253,11 +254,22 @@ static char *variable_expand(const char *name, int argc, char *argv[])
if (!v)
return NULL;
+ if (argc == 0 && v->exp_count)
+ pperror("Recursive variable '%s' references itself (eventually)",
+ name);
+
+ if (v->exp_count > 1000)
+ pperror("Too deep recursive expansion");
+
+ v->exp_count++;
+
if (v->flavor == VAR_RECURSIVE)
res = expand_string_with_args(v->value, argc, argv);
else
res = xstrdup(v->value);
+ v->exp_count--;
+
return res;
}
@@ -284,6 +296,7 @@ void variable_add(const char *name, const char *value,
v = xmalloc(sizeof(*v));
v->name = xstrdup(name);
+ v->exp_count = 0;
list_add_tail(&v->node, &variable_list);
}