commit 2208066603a136f95cfb815ca9281262e6465784

Author: Szabolcs Nagy <szabolcs.nagy@arm.com>

Date:   Thu Feb 11 13:24:47 2021 +0000

    elf: Remove lazy tlsdesc relocation related code

    Remove generic tlsdesc code related to lazy tlsdesc processing since

    lazy tlsdesc relocation is no longer supported.  This includes removing

    GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at

    load time when that lock is already held.

    Added a documentation comment too.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/elf/tlsdeschtab.h b/elf/tlsdeschtab.h

index fea9eefe72edcd6b..c20857e5b4264f00 100644

--- a/elf/tlsdeschtab.h

+++ b/elf/tlsdeschtab.h

@@ -78,6 +78,10 @@ map_generation (struct link_map *map)

   return GL(dl_tls_generation) + 1;

 }

+/* Returns the data pointer for a given map and tls offset that is used

+   to fill in one of the GOT entries referenced by a TLSDESC relocation

+   when using dynamic TLS.  This requires allocation, returns NULL on

+   allocation failure.  */

 void *

 _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)

 {

@@ -85,18 +89,12 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)

   void **entry;

   struct tlsdesc_dynamic_arg *td, test;

-  /* FIXME: We could use a per-map lock here, but is it worth it?  */

-  __rtld_lock_lock_recursive (GL(dl_load_lock));

-

   ht = map->l_mach.tlsdesc_table;

   if (! ht)

     {

       ht = htab_create ();

       if (! ht)

-	{

-	  __rtld_lock_unlock_recursive (GL(dl_load_lock));

-	  return 0;

-	}

+	return 0;

       map->l_mach.tlsdesc_table = ht;

     }

@@ -104,15 +102,11 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)

   test.tlsinfo.ti_offset = ti_offset;

   entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc);

   if (! entry)

-    {

-      __rtld_lock_unlock_recursive (GL(dl_load_lock));

-      return 0;

-    }

+    return 0;

   if (*entry)

     {

       td = *entry;

-      __rtld_lock_unlock_recursive (GL(dl_load_lock));

       return td;

     }

@@ -122,44 +116,9 @@ _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)

      thread.  */

   td->gen_count = map_generation (map);

   td->tlsinfo = test.tlsinfo;

-

-  __rtld_lock_unlock_recursive (GL(dl_load_lock));

   return td;

 }

 # endif /* SHARED */

-/* The idea of the following two functions is to stop multiple threads

-   from attempting to resolve the same TLS descriptor without busy

-   waiting.  Ideally, we should be able to release the lock right

-   after changing td->entry, and then using say a condition variable

-   or a futex wake to wake up any waiting threads, but let's try to

-   avoid introducing such dependencies.  */

-

-static int

-__attribute__ ((unused))

-_dl_tlsdesc_resolve_early_return_p (struct tlsdesc volatile *td, void *caller)

-{

-  if (caller != atomic_load_relaxed (&td->entry))

-    return 1;

-

-  __rtld_lock_lock_recursive (GL(dl_load_lock));

-  if (caller != atomic_load_relaxed (&td->entry))

-    {

-      __rtld_lock_unlock_recursive (GL(dl_load_lock));

-      return 1;

-    }

-

-  atomic_store_relaxed (&td->entry, _dl_tlsdesc_resolve_hold);

-

-  return 0;

-}

-

-static void

-__attribute__ ((unused))

-_dl_tlsdesc_wake_up_held_fixups (void)

-{

-  __rtld_lock_unlock_recursive (GL(dl_load_lock));

-}

-

 #endif

diff --git a/sysdeps/aarch64/tlsdesc.c b/sysdeps/aarch64/tlsdesc.c

index 357465f23d76e2bd..1ead73ab8250e29c 100644

--- a/sysdeps/aarch64/tlsdesc.c

+++ b/sysdeps/aarch64/tlsdesc.c

@@ -22,7 +22,6 @@

 #include <tls.h>

 #include <dl-tlsdesc.h>

 #include <dl-unmap-segments.h>

-#define _dl_tlsdesc_resolve_hold 0

 #include <tlsdeschtab.h>

 /* Unmap the dynamic object, but also release its TLS descriptor table

diff --git a/sysdeps/arm/tlsdesc.c b/sysdeps/arm/tlsdesc.c

index d142d7a2c91e9adb..b78e3f65785bf587 100644

--- a/sysdeps/arm/tlsdesc.c

+++ b/sysdeps/arm/tlsdesc.c

@@ -20,7 +20,6 @@

 #include <tls.h>

 #include <dl-tlsdesc.h>

 #include <dl-unmap-segments.h>

-#define _dl_tlsdesc_resolve_hold 0

 #include <tlsdeschtab.h>

 /* Unmap the dynamic object, but also release its TLS descriptor table

diff --git a/sysdeps/i386/tlsdesc.c b/sysdeps/i386/tlsdesc.c

index 1b4227c8381e1b3d..c242ffce726d50e4 100644

--- a/sysdeps/i386/tlsdesc.c

+++ b/sysdeps/i386/tlsdesc.c

@@ -20,7 +20,6 @@

 #include <tls.h>

 #include <dl-tlsdesc.h>

 #include <dl-unmap-segments.h>

-#define _dl_tlsdesc_resolve_hold 0

 #include <tlsdeschtab.h>

 /* Unmap the dynamic object, but also release its TLS descriptor table

diff --git a/sysdeps/x86_64/tlsdesc.c b/sysdeps/x86_64/tlsdesc.c

index 61a19ae26944c84f..a9325827d0e5e31b 100644

--- a/sysdeps/x86_64/tlsdesc.c

+++ b/sysdeps/x86_64/tlsdesc.c

@@ -20,7 +20,6 @@

 #include <tls.h>

 #include <dl-tlsdesc.h>

 #include <dl-unmap-segments.h>

-#define _dl_tlsdesc_resolve_hold 0

 #include <tlsdeschtab.h>

 /* Unmap the dynamic object, but also release its TLS descriptor table