elf: Avoid using memalign for TLS allocations [BZ #17730]

Instead of a flag which indicates the pointer can be freed, dtv_t
now includes the pointer which should be freed.  Due to padding,
the size of dtv_t does not increase.

To avoid using memalign, the new allocate_dtv_entry function
allocates a sufficiently large buffer so that a sub-buffer
can be found in it which starts with an aligned pointer.  Both
the aligned and original pointers are kept, the latter for calling
free later.

1 files changed, 7 insertions, 5 deletions

diff --git a/sysdeps/generic/dl-dtv.h b/sysdeps/generic/dl-dtv.h
index 36c5c58cdd..39d8fe27de 100644
--- a/sysdeps/generic/dl-dtv.h
+++ b/sysdeps/generic/dl-dtv.h
@@ -19,15 +19,17 @@
 #ifndef _DL_DTV_H
 #define _DL_DTV_H
 
+struct dtv_pointer
+{
+  void *val;                    /* Pointer to data, or TLS_DTV_UNALLOCATED.  */
+  void *to_free;                /* Unaligned pointer, for deallocation.  */
+};
+
 /* Type for the dtv.  */
 typedef union dtv
 {
   size_t counter;
-  struct
-  {
-    void *val;
-    bool is_static;
-  } pointer;
+  struct dtv_pointer pointer;
 } dtv_t;
 
 /* Value used for dtv entries for which the allocation is delayed.  */