aarch64: fix static pie enabled libc when main is in a shared library

In the static pie enabled libc, crt1.o uses the same position independent
code as rcrt1.o and crt1.o is used instead of Scrt1.o when -no-pie
executables are linked.  When main is not defined in the executable, but
in a shared library crt1.o is currently broken, it assumes main is local.
(glibc has a test for this but i missed it in my previous testing.)

To make both rcrt1.o and crt1.o happy with the same code, a wrapper is
introduced around main: with this crt1.o works with extern main symbol
while rcrt1.o does not depend on GOT relocations. (The change only
affects static pie enabled libc. Further simplification of start.S is
possible in the future by using the same approach for Scrt1.o too.)

	* aarch64/start.S (_start): Use __wrap_main.
	(__wrap_main): New local symbol.

diff --git a/ChangeLog b/ChangeLog
index 971257a4bdd9186903f054c8463c9b9686986a28..da74352ce10947451a5536cd73722e625d0c8346 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-01-12  Szabolcs Nagy  <szabolcs.nagy@arm.com>
+
+       * aarch64/start.S (_start): Use __wrap_main.
+       (__wrap_main): New local symbol.
+
 2018-01-12  Dmitry V. Levin  <ldv@altlinux.org>
 
        [BZ #22679]

diff --git a/sysdeps/aarch64/start.S b/sysdeps/aarch64/start.S
index 9f3b4188db9d8dd9b7ec23df4e854d3932eab7a2..bad000f555a3c8d94fa3d36319f5fada3d836660 100644 (file)
--- a/sysdeps/aarch64/start.S
+++ b/sysdeps/aarch64/start.S
@@ -71,8 +71,8 @@ _start:
         adrp    x4, :got:__libc_csu_fini
        ldr     PTR_REG (4), [x4, #:got_lo12:__libc_csu_fini]
 # else
-       adrp    x0, main
-       add     x0, x0, :lo12:main
+       adrp    x0, __wrap_main
+       add     x0, x0, :lo12:__wrap_main
        adrp    x3, __libc_csu_init
        add     x3, x3, :lo12:__libc_csu_init
        adrp    x4, __libc_csu_fini
@@ -94,6 +94,15 @@ _start:
        /* should never get here....*/
        bl      abort
 
+#if defined PIC && !defined SHARED
+       /* When main is not defined in the executable but in a shared library
+          then a wrapper is needed in crt1.o of the static-pie enabled libc,
+          because crt1.o and rcrt1.o share code and the later must avoid the
+          use of GOT relocations before __libc_start_main is called.  */
+__wrap_main:
+       b       main
+#endif
+
        /* Define a symbol for the first piece of initialized data.  */
        .data
        .globl __data_start