diff mbox series

[v4,05/10] Use hidden visibility for early static PIE code

Message ID 78d3bf1bc9e9f7c1eafbcf011bbd815e7f6e90b0.1610986541.git.szabolcs.nagy@arm.com
State Superseded
Headers show
Series fix ifunc with static pie [BZ #27072] | expand

Commit Message

Szabolcs Nagy Jan. 18, 2021, 4:24 p.m. UTC
This is necessary to avoid RELATIVE relocations in code that has to run
before static PIE self relocation.  We cannot make all symbols hidden:

On i386, all calls to IFUNC functions must go through PLT and calls to
hidden functions CANNOT go through PLT in PIE since EBX used in PIE PLT
may not be set up for local calls to hidden IFUNC functions.

Even if we can't make all libc symbols hidden for static PIE on i386, we
must make all symbols used before and by _dl_relocate_static_pie hidden.

This is needed for fixing bug 27072.

Co-authored-by: H.J. Lu <hjl.tools@gmail.com>
---
 csu/libc-start.c                             | 4 ++++
 elf/dl-reloc-static-pie.c                    | 2 ++
 elf/dl-support.c                             | 6 ++++++
 elf/dl-tunables.c                            | 4 ++++
 elf/enbl-secure.c                            | 4 ++++
 misc/sbrk.c                                  | 4 ++++
 sysdeps/unix/sysv/linux/aarch64/libc-start.c | 5 +++++
 sysdeps/x86/libc-start.c                     | 5 +++++
 8 files changed, 34 insertions(+)

Comments

Adhemerval Zanella Jan. 18, 2021, 9:49 p.m. UTC | #1
On 18/01/2021 13:24, Szabolcs Nagy via Libc-alpha wrote:
> This is necessary to avoid RELATIVE relocations in code that has to run
> before static PIE self relocation.  We cannot make all symbols hidden:
> 
> On i386, all calls to IFUNC functions must go through PLT and calls to
> hidden functions CANNOT go through PLT in PIE since EBX used in PIE PLT
> may not be set up for local calls to hidden IFUNC functions.
> 
> Even if we can't make all libc symbols hidden for static PIE on i386, we
> must make all symbols used before and by _dl_relocate_static_pie hidden.
> 
> This is needed for fixing bug 27072.
> 
> Co-authored-by: H.J. Lu <hjl.tools@gmail.com>
> ---
>  csu/libc-start.c                             | 4 ++++
>  elf/dl-reloc-static-pie.c                    | 2 ++
>  elf/dl-support.c                             | 6 ++++++
>  elf/dl-tunables.c                            | 4 ++++
>  elf/enbl-secure.c                            | 4 ++++
>  misc/sbrk.c                                  | 4 ++++
>  sysdeps/unix/sysv/linux/aarch64/libc-start.c | 5 +++++
>  sysdeps/x86/libc-start.c                     | 5 +++++
>  8 files changed, 34 insertions(+)
> 
> diff --git a/csu/libc-start.c b/csu/libc-start.c
> index db859c3bed..1e90dcb0a7 100644
> --- a/csu/libc-start.c
> +++ b/csu/libc-start.c
> @@ -15,6 +15,10 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push(hidden)
> +#endif
>  #include <assert.h>
>  #include <stdlib.h>
>  #include <stdio.h>

Ok.

> diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
> index a8d964061e..d5bd2f31e9 100644
> --- a/elf/dl-reloc-static-pie.c
> +++ b/elf/dl-reloc-static-pie.c
> @@ -17,6 +17,8 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #if ENABLE_STATIC_PIE
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +# pragma GCC visibility push(hidden)
>  #include <unistd.h>
>  #include <ldsodefs.h>
>  #include "dynamic-link.h"

Ok.

> diff --git a/elf/dl-support.c b/elf/dl-support.c
> index 9d468d5a4b..384080dd80 100644
> --- a/elf/dl-support.c
> +++ b/elf/dl-support.c
> @@ -19,6 +19,12 @@
>  /* This file defines some things that for the dynamic linker are defined in
>     rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
>  
> +#include <string.h>
> +/* Mark symbols hidden in static PIE for early self relocation to work.
> +   Note: string.h may have ifuncs which cannot be hidden on i686.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push(hidden)
> +#endif
>  #include <errno.h>
>  #include <libintl.h>
>  #include <stdlib.h>

Ok.

> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index e44476f204..b1a50b8469 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -18,6 +18,10 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push(hidden)
> +#endif
>  #include <startup.h>
>  #include <stdint.h>
>  #include <stdbool.h>

Ok.

> diff --git a/elf/enbl-secure.c b/elf/enbl-secure.c
> index bc8c5e96d2..ffd7938605 100644
> --- a/elf/enbl-secure.c
> +++ b/elf/enbl-secure.c
> @@ -19,6 +19,10 @@
>  /* This file is used in the static libc.  For the shared library,
>     dl-sysdep.c defines and initializes __libc_enable_secure.  */
>  
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push(hidden)
> +#endif
>  #include <unistd.h>
>  #include <libc-internal.h>
>  

Ok.

> diff --git a/misc/sbrk.c b/misc/sbrk.c
> index 99b3fb517e..95800b32aa 100644
> --- a/misc/sbrk.c
> +++ b/misc/sbrk.c
> @@ -15,6 +15,10 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +#if BUILD_PIE_DEFAULT
> +# pragma GCC visibility push(hidden)
> +#endif
>  #include <errno.h>
>  #include <libc-internal.h>
>  #include <stdbool.h>

Ok.

> diff --git a/sysdeps/unix/sysv/linux/aarch64/libc-start.c b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
> index f816f04ee1..e1604a6ed0 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/libc-start.c
> +++ b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
> @@ -17,6 +17,11 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #ifndef SHARED
> +
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +# if BUILD_PIE_DEFAULT
> +#  pragma GCC visibility push(hidden)
> +# endif
>  # include <ldsodefs.h>
>  # include <cpu-features.c>
>  

Ok, but wouldn't be possible to focus the pragma on
csu/libc-start.c by moving the includes on generic implementation?

> diff --git a/sysdeps/x86/libc-start.c b/sysdeps/x86/libc-start.c
> index 4bbd7d555b..d30aec2aa1 100644
> --- a/sysdeps/x86/libc-start.c
> +++ b/sysdeps/x86/libc-start.c
> @@ -16,6 +16,11 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #ifndef SHARED
> +
> +/* Mark symbols hidden in static PIE for early self relocation to work.  */
> +# if BUILD_PIE_DEFAULT
> +#  pragma GCC visibility push(hidden)
> +# endif
>  /* Define I386_USE_SYSENTER to support syscall during startup in static
>     PIE.  */
>  # include <startup.h>
> 

Ditto.
diff mbox series

Patch

diff --git a/csu/libc-start.c b/csu/libc-start.c
index db859c3bed..1e90dcb0a7 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -15,6 +15,10 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
 #include <assert.h>
 #include <stdlib.h>
 #include <stdio.h>
diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
index a8d964061e..d5bd2f31e9 100644
--- a/elf/dl-reloc-static-pie.c
+++ b/elf/dl-reloc-static-pie.c
@@ -17,6 +17,8 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #if ENABLE_STATIC_PIE
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+# pragma GCC visibility push(hidden)
 #include <unistd.h>
 #include <ldsodefs.h>
 #include "dynamic-link.h"
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 9d468d5a4b..384080dd80 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -19,6 +19,12 @@ 
 /* This file defines some things that for the dynamic linker are defined in
    rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
 
+#include <string.h>
+/* Mark symbols hidden in static PIE for early self relocation to work.
+   Note: string.h may have ifuncs which cannot be hidden on i686.  */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
 #include <errno.h>
 #include <libintl.h>
 #include <stdlib.h>
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index e44476f204..b1a50b8469 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -18,6 +18,10 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
 #include <startup.h>
 #include <stdint.h>
 #include <stdbool.h>
diff --git a/elf/enbl-secure.c b/elf/enbl-secure.c
index bc8c5e96d2..ffd7938605 100644
--- a/elf/enbl-secure.c
+++ b/elf/enbl-secure.c
@@ -19,6 +19,10 @@ 
 /* This file is used in the static libc.  For the shared library,
    dl-sysdep.c defines and initializes __libc_enable_secure.  */
 
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
 #include <unistd.h>
 #include <libc-internal.h>
 
diff --git a/misc/sbrk.c b/misc/sbrk.c
index 99b3fb517e..95800b32aa 100644
--- a/misc/sbrk.c
+++ b/misc/sbrk.c
@@ -15,6 +15,10 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+#if BUILD_PIE_DEFAULT
+# pragma GCC visibility push(hidden)
+#endif
 #include <errno.h>
 #include <libc-internal.h>
 #include <stdbool.h>
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc-start.c b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
index f816f04ee1..e1604a6ed0 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc-start.c
+++ b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
@@ -17,6 +17,11 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #ifndef SHARED
+
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+# if BUILD_PIE_DEFAULT
+#  pragma GCC visibility push(hidden)
+# endif
 # include <ldsodefs.h>
 # include <cpu-features.c>
 
diff --git a/sysdeps/x86/libc-start.c b/sysdeps/x86/libc-start.c
index 4bbd7d555b..d30aec2aa1 100644
--- a/sysdeps/x86/libc-start.c
+++ b/sysdeps/x86/libc-start.c
@@ -16,6 +16,11 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #ifndef SHARED
+
+/* Mark symbols hidden in static PIE for early self relocation to work.  */
+# if BUILD_PIE_DEFAULT
+#  pragma GCC visibility push(hidden)
+# endif
 /* Define I386_USE_SYSENTER to support syscall during startup in static
    PIE.  */
 # include <startup.h>