Add a DSO_dsobyaddr() function

This works the same way as DSO_pathbyaddr() but instead returns a ptr to
the DSO that contains the provided symbol.
Reviewed-by: NTim Hudson <tjh@openssl.org>

crypto/dso/dso_lib.c

@@ -73,9 +73,11 @@ int DSO_free(DSO *dso)
         return 1;
     REF_ASSERT_ISNT(i < 0);
 
-    if ((dso->meth->dso_unload != NULL) && !dso->meth->dso_unload(dso)) {
-        DSOerr(DSO_F_DSO_FREE, DSO_R_UNLOAD_FAILED);
-        return 0;
+    if ((dso->flags & DSO_FLAG_NO_UNLOAD_ON_FREE) == 0) {
+        if ((dso->meth->dso_unload != NULL) && !dso->meth->dso_unload(dso)) {
+            DSOerr(DSO_F_DSO_FREE, DSO_R_UNLOAD_FAILED);
+            return 0;
+        }
     }
 
     if ((dso->meth->finish != NULL) && !dso->meth->finish(dso)) {
@@ -316,6 +318,21 @@ int DSO_pathbyaddr(void *addr, char *path, int sz)
     return (*meth->pathbyaddr) (addr, path, sz);
 }
 
+DSO *DSO_dsobyaddr(void *addr, int flags)
+{
+    DSO *ret = NULL;
+    char *filename = NULL;
+    int len = DSO_pathbyaddr(addr, NULL, 0);
+
+    filename = OPENSSL_malloc(len);
+    if (filename != NULL
+            && DSO_pathbyaddr(addr, filename, len) == len)
+        ret = DSO_load(NULL, filename, NULL, flags);
+
+    OPENSSL_free(filename);
+    return ret;
+}
+
 void *DSO_global_lookup(const char *name)
 {
     DSO_METHOD *meth = default_DSO_meth;

include/internal/dso.h

@@ -42,6 +42,11 @@ extern "C" {
  */
 # define DSO_FLAG_NAME_TRANSLATION_EXT_ONLY      0x02
 
+/*
+ * Don't unload the DSO when we call DSO_free()
+ */
+# define DSO_FLAG_NO_UNLOAD_ON_FREE              0x04
+
 /*
  * This flag loads the library with public symbols. Meaning: The exported
  * symbols of this library are public to all libraries loaded after this
@@ -141,6 +146,12 @@ DSO_METHOD *DSO_METHOD_openssl(void);
  */
 int DSO_pathbyaddr(void *addr, char *path, int sz);
 
+/*
+ * Like DSO_pathbyaddr() but instead returns a handle to the DSO for the symbol
+ * or NULL on error.
+ */
+DSO *DSO_dsobyaddr(void *addr, int flags);
+
 /*
  * This function should be used with caution! It looks up symbols in *all*
  * loaded modules and if module gets unloaded by somebody else attempt to

util/libcrypto.num

@@ -4217,3 +4217,4 @@ BIO_write_ex                            4167	1_1_1	EXIST::FUNCTION:
 BIO_meth_get_write_ex                   4168	1_1_1	EXIST::FUNCTION:
 BIO_meth_set_write_ex                   4169	1_1_1	EXIST::FUNCTION:
 DSO_pathbyaddr                          4170	1_1_0c	EXIST::FUNCTION:
+DSO_dsobyaddr                           4171	1_1_0c	EXIST::FUNCTION: