nptl: add rtld_hidden_proto to __rseq_size and __rseq_offset

This allows accessing the internal aliases of __rseq_size and
__rseq_offset from ld.so without ifdefs and avoids dynamic symbol
binding at run time for both variables.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

diff --git a/sysdeps/unix/sysv/linux/dl-rseq-symbols.S b/sysdeps/unix/sysv/linux/dl-rseq-symbols.S
index 353bf657b97d7199eb481d63180ed29b20a91f09..2502a76e5040c1d7dcfd3fff8fac9d97663fbcae 100644 (file)
--- a/sysdeps/unix/sysv/linux/dl-rseq-symbols.S
+++ b/sysdeps/unix/sysv/linux/dl-rseq-symbols.S
@@ -27,14 +27,18 @@
 /* Some targets define a macro to denote the zero register.  */
 #undef zero
 
-/* Define 2 symbols: '__rseq_size' is public const and '_rseq_size' (an
-   alias of '__rseq_size') is hidden and writable for internal use by the
-   dynamic linker which will initialize the value both symbols point to
-   before copy relocations take place. */
+/* Define 3 symbols: '__rseq_size' is public const and then '_rseq_size' and
+   '__GI___rseq_size' (both aliases of '__rseq_size') are hidden, '_rseq_size'
+   is writable for internal use by the dynamic linker which will initialize
+   the value the symbols point to before copy relocations take place.  */
 
        .globl  __rseq_size
        .type   __rseq_size, %object
        .size   __rseq_size, 4
+       .hidden __GI___rseq_size
+       .globl  __GI___rseq_size
+       .type   __GI___rseq_size, %object
+       .size   __GI___rseq_size, 4
        .hidden _rseq_size
        .globl  _rseq_size
        .type   _rseq_size, %object
@@ -42,17 +46,23 @@
        .section .data.rel.ro
        .balign 4
 __rseq_size:
+__GI___rseq_size:
 _rseq_size:
        .zero   4
 
-/* Define 2 symbols: '__rseq_offset' is public const and '_rseq_offset' (an
-   alias of '__rseq_offset') is hidden and writable for internal use by the
-   dynamic linker which will initialize the value both symbols point to
-   before copy relocations take place. */
+/* Define 3 symbols: '__rseq_offset' is public const and then '_rseq_offset'
+   and '__GI___rseq_offset' (both aliases of '__rseq_offset') are hidden,
+   '_rseq_offset' is writable for internal use by the dynamic linker which will
+   initialize the value the symbols point to before copy relocations take
+   place.  */
 
        .globl  __rseq_offset
        .type   __rseq_offset, %object
        .size   __rseq_offset, RSEQ_OFFSET_SIZE
+       .hidden __GI___rseq_offset
+       .globl  __GI___rseq_offset
+       .type   __GI___rseq_offset, %object
+       .size   __GI___rseq_offset, RSEQ_OFFSET_SIZE
        .hidden _rseq_offset
        .globl  _rseq_offset
        .type   _rseq_offset, %object
@@ -60,5 +70,6 @@ _rseq_size:
        .section .data.rel.ro
        .balign RSEQ_OFFSET_SIZE
 __rseq_offset:
+__GI___rseq_offset:
 _rseq_offset:
        .zero   RSEQ_OFFSET_SIZE

diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h
index 6f565581c14cda07535be25c1307c6959a5a6cc5..3993431707563199161fbc8836c3fb9e16e5e90f 100644 (file)
--- a/sysdeps/unix/sysv/linux/rseq-internal.h
+++ b/sysdeps/unix/sysv/linux/rseq-internal.h
@@ -24,6 +24,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <sys/rseq.h>
+#include <ldsodefs.h>
 
 /* Minimum size of the rseq area allocation required by the syscall.  The
    actually used rseq feature size may be less (20 bytes initially).  */
@@ -52,19 +53,20 @@ extern unsigned int _rseq_size attribute_hidden;
    In .data.relro but not yet write-protected.  */
 extern ptrdiff_t _rseq_offset attribute_hidden;
 
+/* We want to use rtld_hidden_proto in order to call the internal aliases
+   of __rseq_size and __rseq_offset from ld.so.  This avoids dynamic symbol
+   binding at run time for both variables.  */
+rtld_hidden_proto (__rseq_size)
+rtld_hidden_proto (__rseq_offset)
+
 #ifdef RSEQ_SIG
 static inline bool
 rseq_register_current_thread (struct pthread *self, bool do_rseq)
 {
   if (do_rseq)
     {
-      unsigned int size;
-#if IS_IN (rtld)
-      /* Use the hidden symbol in ld.so.  */
-      size = _rseq_size;
-#else
-      size = __rseq_size;
-#endif
+      unsigned int size =  __rseq_size;
+
       if (size < RSEQ_AREA_SIZE_INITIAL)
         /* The initial implementation used only 20 bytes out of 32,
            but still expected size 32.  */