From d50240a5f6ceaf690a77b0fccb17be51cfa151c2 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Wed, 12 Jun 2013 16:28:04 +0100 Subject: arm64: mm: permit use of tagged pointers at EL0 TCR.TBI0 can be used to cause hardware address translation to ignore the top byte of userspace virtual addresses. Whilst not especially useful in standard C programs, this can be used by JITs to `tag' pointers with various pieces of metadata. This patch enables this bit for AArch64 Linux, and adds a new file to Documentation/arm64/ which describes some potential caveats when using tagged virtual addresses. Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/pgtable-hwdef.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/arm64/include/asm/pgtable-hwdef.h') diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h index e182a356c979..d57e66845c86 100644 --- a/arch/arm64/include/asm/pgtable-hwdef.h +++ b/arch/arm64/include/asm/pgtable-hwdef.h @@ -122,5 +122,6 @@ #define TCR_TG1_64K (UL(1) << 30) #define TCR_IPS_40BIT (UL(2) << 32) #define TCR_ASID16 (UL(1) << 36) +#define TCR_TBI0 (UL(1) << 37) #endif -- cgit v1.2.3