x86: Don't use apply_irel in static PIE

Message ID 20190321122445.28990-1-hjl.tools@gmail.com
State New
Headers show
Series
  • x86: Don't use apply_irel in static PIE
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Commit Message

H.J. Lu March 21, 2019, 12:24 p.m.
On x86, since _dl_relocate_static_pie also processes IFUNC relocations,
there is no need to call apply_irel.

Tested on i686 and x86-64.

	* csu/libc-start.c (apply_irel): Add unused attribute.
	* sysdeps/x86/libc-start.h (ARCH_SETUP_IREL): Defined as empty
	for static PIE.
---
 csu/libc-start.c         | 1 +
 sysdeps/x86/libc-start.h | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

-- 
2.20.1

Comments

Siva Chandra March 21, 2019, 3:18 p.m. | #1
On Thu, Mar 21, 2019 at 5:36 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>

> On x86, since _dl_relocate_static_pie also processes IFUNC relocations,

> there is no need to call apply_irel.

>

> Tested on i686 and x86-64.

>

>         * csu/libc-start.c (apply_irel): Add unused attribute.

>         * sysdeps/x86/libc-start.h (ARCH_SETUP_IREL): Defined as empty

>         for static PIE.

> ---

>  csu/libc-start.c         | 1 +

>  sysdeps/x86/libc-start.h | 7 ++++++-

>  2 files changed, 7 insertions(+), 1 deletion(-)

>

> diff --git a/csu/libc-start.c b/csu/libc-start.c

> index 5d9c3675fa..07be05f1e9 100644

> --- a/csu/libc-start.c

> +++ b/csu/libc-start.c

> @@ -66,6 +66,7 @@ uintptr_t __pointer_chk_guard_local

>  # endif

>

>  static void

> +__attribute__ ((unused))

>  apply_irel (void)

>  {

>  # ifdef IREL

> diff --git a/sysdeps/x86/libc-start.h b/sysdeps/x86/libc-start.h

> index c76b1d917f..e544867c1d 100644

> --- a/sysdeps/x86/libc-start.h

> +++ b/sysdeps/x86/libc-start.h

> @@ -17,7 +17,12 @@

>     <http://www.gnu.org/licenses/>.  */

>

>  #ifndef SHARED

> -# define ARCH_SETUP_IREL() apply_irel ()

> +# if ENABLE_STATIC_PIE

> +/* NB: x86 doesn't use apply_irel in static PIE.  */

> +#  define ARCH_SETUP_IREL()


Will this break non-PIE static when glibc is configured --enable-static-pie?

> +# else

> +#  define ARCH_SETUP_IREL() apply_irel ()

> +# endif

>  # define ARCH_APPLY_IREL()

>  # ifndef ARCH_SETUP_TLS

>  #  define ARCH_SETUP_TLS() __libc_setup_tls ()

> --

> 2.20.1

>
H.J. Lu March 21, 2019, 9:27 p.m. | #2
On 3/21/19, Siva Chandra <sivachandra@google.com> wrote:
> On Thu, Mar 21, 2019 at 5:36 AM H.J. Lu <hjl.tools@gmail.com> wrote:

>>

>> On x86, sinceelf/ifuncmain1static-non-pie _dl_relocate_static_pie also processes IFUNC relocations,

>> there is no need to call apply_irel.

>>

>> Tested on i686 and x86-64.

>>

>>         * csu/libc-start.c (apply_irel): Add unused attribute.

>>         * sysdeps/x86/libc-start.h (ARCH_SETUP_IREL): Defined as empty

>>         for static PIE.

>> ---

>>  csu/libc-start.c         | 1 +

>>  sysdeps/x86/libc-start.h | 7 ++++++-

>>  2 files changed, 7 insertions(+), 1 deletion(-)

>>

>> diff --git a/csu/libc-start.c b/csu/libc-start.c

>> index 5d9c3675fa..07be05f1e9 100644

>> --- a/csu/libc-start.c

>> +++ b/csu/libc-start.c

>> @@ -66,6 +66,7 @@ uintptr_t __pointer_chk_guard_local

>>  # endif

>>

>>  static void

>> +__attribute__ ((unused))

>>  apply_irel (void)

>>  {

>>  # ifdef IREL

>> diff --git a/sysdeps/x86/libc-start.h b/sysdeps/x86/libc-start.h

>> index c76b1d917f..e544867c1d 100644

>> --- a/sysdeps/x86/libc-start.h

>> +++ b/sysdeps/x86/libc-start.h

>> @@ -17,7 +17,12 @@

>>     <http://www.gnu.org/licenses/>.  */

>>

>>  #ifndef SHARED

>> -# define ARCH_SETUP_IREL() apply_irel ()

>> +# if ENABLE_STATIC_PIE

>> +/* NB: x86 doesn't use apply_irel in static PIE.  */

>> +#  define ARCH_SETUP_IREL()

>

> Will this break non-PIE static when glibc is configured

> --enable-static-pie?


You are right.  I withdrew my patch.

>> +# else

>> +#  define ARCH_SETUP_IREL() apply_irel ()

>> +# endif

>>  # define ARCH_APPLY_IREL()

>>  # ifndef ARCH_SETUP_TLS

>>  #  define ARCH_SETUP_TLS() __libc_setup_tls ()

>> --

>> 2.20.1

>>

>


Thanks.

-- 
H.J.

Patch

diff --git a/csu/libc-start.c b/csu/libc-start.c
index 5d9c3675fa..07be05f1e9 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -66,6 +66,7 @@  uintptr_t __pointer_chk_guard_local
 # endif
 
 static void
+__attribute__ ((unused))
 apply_irel (void)
 {
 # ifdef IREL
diff --git a/sysdeps/x86/libc-start.h b/sysdeps/x86/libc-start.h
index c76b1d917f..e544867c1d 100644
--- a/sysdeps/x86/libc-start.h
+++ b/sysdeps/x86/libc-start.h
@@ -17,7 +17,12 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #ifndef SHARED
-# define ARCH_SETUP_IREL() apply_irel ()
+# if ENABLE_STATIC_PIE
+/* NB: x86 doesn't use apply_irel in static PIE.  */
+#  define ARCH_SETUP_IREL()
+# else
+#  define ARCH_SETUP_IREL() apply_irel ()
+# endif
 # define ARCH_APPLY_IREL()
 # ifndef ARCH_SETUP_TLS
 #  define ARCH_SETUP_TLS() __libc_setup_tls ()