[RFC][PATCH v5 02/16] include/link.h: Update the link_map struct to allow proxies

Vivek Das Mohapatra vivek@collabora.com
Wed Jun 17 14:00:10 GMT 2020

We already have an l_real pointer, used for a similar purpose by
the linker for copies of ld.so in secondary namespaces. Update its
documentation and add a bitfield to indicate when link_map entry
is a proxy.
 include/link.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/link.h b/include/link.h
index aea268439c..c63166317d 100644
--- a/include/link.h
+++ b/include/link.h
@@ -103,8 +103,9 @@ struct link_map
        They may change without notice.  */
     /* This is an element which is only ever different from a pointer to
-       the very same copy of this type for ld.so when it is used in more
-       than one namespace.  */
+       the very same copy of this type when:
+       - A shallow copy of ld.so is placed in namespaces other than LM_ID_BASE.
+       - An object is proxied into a namespace by dlmopen with RTLD_SHARED.  */
     struct link_map *l_real;
     /* Number of the namespace this link map belongs to.  */
@@ -176,6 +177,7 @@ struct link_map
     unsigned int l_relocated:1;	/* Nonzero if object's relocations done.  */
     unsigned int l_init_called:1; /* Nonzero if DT_INIT function called.  */
     unsigned int l_global:1;	/* Nonzero if object in _dl_global_scope.  */
+    unsigned int l_proxy:1;    /* Nonzero if object is a shallow copy.  */
     unsigned int l_reserved:2;	/* Reserved for internal use.  */
     unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
 					to by `l_phdr' is allocated.  */

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