avoid malloc of ctor queue for programs with no external deps

together with the previous two commits, this completes restoration of
the property that dynamic-linked apps with no external deps and no tls
have no failure paths before entry.

diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 4f090ad..35cacd7 100644 (file)
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -30,6 +30,7 @@ static void error(const char *, ...);
 #define ALIGN(x,y) ((x)+(y)-1 & -(y))
 
 #define container_of(p,t,m) ((t*)((char *)(p)-offsetof(t,m)))
+#define countof(a) ((sizeof (a))/(sizeof (a)[0]))
 
 struct debug {
        int ver;
@@ -135,6 +136,7 @@ static pthread_mutex_t init_fini_lock;
 static pthread_cond_t ctor_cond;
 static struct dso *builtin_deps[2];
 static struct dso *const no_deps[1];
+static struct dso *builtin_ctor_queue[4];
 static struct dso **main_ctor_queue;
 static struct fdpic_loadmap *app_loadmap;
 static struct fdpic_dummy_loadmap app_dummy_loadmap;
@@ -1405,7 +1407,10 @@ static struct dso **queue_ctors(struct dso *dso)
                        p->mark = 0;
        }
        cnt++; /* termination slot */
-       stack = queue = calloc(cnt, sizeof *queue);
+       if (dso==head && cnt <= countof(builtin_ctor_queue))
+               queue = builtin_ctor_queue;
+       else
+               queue = calloc(cnt, sizeof *queue);
 
        if (!queue) {
                error("Error allocating constructor queue: %m\n");
@@ -1416,6 +1421,7 @@ static struct dso **queue_ctors(struct dso *dso)
        /* Opposite ends of the allocated buffer serve as an output queue
         * and a working stack. Setup initial stack with just the argument
         * dso and initial queue empty... */
+       stack = queue;
        qpos = 0;
        spos = cnt;
        stack[--spos] = dso;
@@ -1487,7 +1493,8 @@ static void do_init_fini(struct dso **queue)
 void __libc_start_init(void)
 {
        do_init_fini(main_ctor_queue);
-       if (!__malloc_replaced) free(main_ctor_queue);
+       if (!__malloc_replaced && main_ctor_queue != builtin_ctor_queue)
+               free(main_ctor_queue);
        main_ctor_queue = 0;
 }