[PATCH 4.9 28/59] efi/libstub/arm64: Use hidden attribute for struct screen_info reference

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

commit 760b61d76da6d6a99eb245ab61abf71ca5415cea upstream.

To prevent the compiler from emitting absolute references to screen_info
when building position independent code, redeclare the symbol with hidden
visibility.

Tested-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170818194947.19347-3-ard.biesheuvel@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/include/asm/efi.h |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -54,6 +54,9 @@ int efi_set_mapping_permissions(struct m
 #define alloc_screen_info(x...)		&screen_info
 #define free_screen_info(x...)
 
+/* redeclare as 'hidden' so the compiler will generate relative references */
+extern struct screen_info screen_info __attribute__((__visibility__("hidden")));
+
 static inline void efifb_setup_from_dmi(struct screen_info *si, const char *opt)
 {
 }