diff options
authorKristina Martsenko <>2017-05-03 16:37:47 +0100
committerGreg Kroah-Hartman <>2017-06-12 17:25:52 +0200
commitbf952b9330ee17d62e68eb32135ee8a4eb3193d2 (patch)
parentdbbe14e4a72dc37fd85cfd20d8432ad9bcd94ffd (diff)
arm64: entry: improve data abort handling of tagged pointers
commit 276e93279a630657fff4b086ba14c95955912dfa upstream. This backport has a minor difference from the upstream commit: it adds the asm-uaccess.h file, which is not present in 4.4, because 4.4 does not have commit b4b8664d291a ("arm64: don't pull uaccess.h into *.S"). Original patch description: When handling a data abort from EL0, we currently zero the top byte of the faulting address, as we assume the address is a TTBR0 address, which may contain a non-zero address tag. However, the address may be a TTBR1 address, in which case we should not zero the top byte. This patch fixes that. The effect is that the full TTBR1 address is passed to the task's signal handler (or printed out in the kernel log). When handling a data abort from EL1, we leave the faulting address intact, as we assume it's either a TTBR1 address or a TTBR0 address with tag 0x00. This is true as far as I'm aware, we don't seem to access a tagged TTBR0 address anywhere in the kernel. Regardless, it's easy to forget about address tags, and code added in the future may not always remember to remove tags from addresses before accessing them. So add tag handling to the EL1 data abort handler as well. This also makes it consistent with the EL0 data abort handler. Fixes: d50240a5f6ce ("arm64: mm: permit use of tagged pointers at EL0") Reviewed-by: Dave Martin <> Acked-by: Will Deacon <> Signed-off-by: Kristina Martsenko <> Signed-off-by: Catalin Marinas <> Signed-off-by: Greg Kroah-Hartman <>
2 files changed, 17 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
new file mode 100644
index 0000000..be2d234
--- /dev/null
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -0,0 +1,13 @@
+#ifndef __ASM_ASM_UACCESS_H
+#define __ASM_ASM_UACCESS_H
+ * Remove the address tag from a virtual address, if present.
+ */
+ .macro clear_address_tag, dst, addr
+ tst \addr, #(1 << 55)
+ bic \dst, \addr, #(0xff << 56)
+ csel \dst, \dst, \addr, eq
+ .endm
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index bd14849..dccd0c2 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -29,6 +29,7 @@
#include <asm/esr.h>
#include <asm/memory.h>
#include <asm/thread_info.h>
+#include <asm/asm-uaccess.h>
#include <asm/unistd.h>
@@ -316,12 +317,13 @@ el1_da:
* Data abort handling
- mrs x0, far_el1
+ mrs x3, far_el1
// re-enable interrupts if they were enabled in the aborted context
tbnz x23, #7, 1f // PSR_I_BIT
+ clear_address_tag x0, x3
mov x2, sp // struct pt_regs
bl do_mem_abort
@@ -483,7 +485,7 @@ el0_da:
// enable interrupts before calling the main handler
- bic x0, x26, #(0xff << 56)
+ clear_address_tag x0, x26
mov x1, x25
mov x2, sp
bl do_mem_abort