MIPS: VDSO: Reduce VDSO_RANDOMIZE_SIZE to 64MB for 64bit

Commit ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory")
set VDSO_RANDOMIZE_SIZE to 256MB for 64bit kernel. But take a look at
arch/mips/mm/mmap.c we can see that MIN_GAP is 128MB, which means the
mmap_base may be at (user_address_top - 128MB). This make the stack be
surrounded by mmaped areas, then stack expanding fails and causes a
segmentation fault. Therefore, VDSO_RANDOMIZE_SIZE should be less than
MIN_GAP and this patch reduce it to 64MB.

Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Paul Burton <[email protected]>
Fixes: ea7e0480a4b6 ("MIPS: VDSO: Always map near top of user memory")
Patchwork: https://patchwork.linux-mips.org/patch/20910/
Cc: Ralf Baechle <[email protected]>
Cc: James Hogan <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Cc: Huacai Chen <[email protected]>

diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 49d6046ca1d0c1661403111519478666964f5a16..c373eb605040246ad67e332f72bc6de8aee0dfa8 100644 (file)
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -81,7 +81,7 @@ extern unsigned int vced_count, vcei_count;
 
 #endif
 
-#define VDSO_RANDOMIZE_SIZE    (TASK_IS_32BIT_ADDR ? SZ_1M : SZ_256M)
+#define VDSO_RANDOMIZE_SIZE    (TASK_IS_32BIT_ADDR ? SZ_1M : SZ_64M)
 
 extern unsigned long mips_stack_top(void);
 #define STACK_TOP              mips_stack_top()