xtensa: don't allow overflow/underflow on unaligned stack
Double exceptions that happen during register window overflow/underflow
are handled in the topmost stack frame, as if it was the only exception
that occured. However unaligned access exception handler is special
because it needs to analyze instruction that caused the exception, but
the userspace instruction that triggered window exception is completely
irrelevant. Unaligned data access is rather normal in the generic
userspace code, but stack pointer manipulation must always be done by
architecture-aware code and thus unaligned stack means a serious problem
anyway.
Use the default unaligned access handler that raises SIGBUS in case
of unaligned access in window overflow/underflow handler.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index eebbfd8..9d2f45f 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -101,9 +101,8 @@
#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
#ifdef CONFIG_XTENSA_UNALIGNED_USER
{ EXCCAUSE_UNALIGNED, USER, fast_unaligned },
-#else
-{ EXCCAUSE_UNALIGNED, 0, do_unaligned_user },
#endif
+{ EXCCAUSE_UNALIGNED, 0, do_unaligned_user },
{ EXCCAUSE_UNALIGNED, KRNL, fast_unaligned },
#endif
#ifdef CONFIG_MMU
@@ -264,7 +263,6 @@
*/
#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
-#ifndef CONFIG_XTENSA_UNALIGNED_USER
void
do_unaligned_user (struct pt_regs *regs)
{
@@ -286,7 +284,6 @@
}
#endif
-#endif
void
do_debug(struct pt_regs *regs)
diff --git a/arch/xtensa/kernel/vectors.S b/arch/xtensa/kernel/vectors.S
index 8453e6e..1b397a9 100644
--- a/arch/xtensa/kernel/vectors.S
+++ b/arch/xtensa/kernel/vectors.S
@@ -454,8 +454,14 @@
s32i a0, a2, PT_DEPC
_DoubleExceptionVector_handle_exception:
+ addi a0, a0, -EXCCAUSE_UNALIGNED
+ beqz a0, 2f
addx4 a0, a0, a3
- l32i a0, a0, EXC_TABLE_FAST_USER
+ l32i a0, a0, EXC_TABLE_FAST_USER + 4 * EXCCAUSE_UNALIGNED
+ xsr a3, excsave1
+ jx a0
+2:
+ movi a0, user_exception
xsr a3, excsave1
jx a0
diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S
index d16db6d..fc1bc2b 100644
--- a/arch/xtensa/kernel/vmlinux.lds.S
+++ b/arch/xtensa/kernel/vmlinux.lds.S
@@ -269,13 +269,13 @@
.UserExceptionVector.literal)
SECTION_VECTOR (_DoubleExceptionVector_literal,
.DoubleExceptionVector.literal,
- DOUBLEEXC_VECTOR_VADDR - 40,
+ DOUBLEEXC_VECTOR_VADDR - 48,
SIZEOF(.UserExceptionVector.text),
.UserExceptionVector.text)
SECTION_VECTOR (_DoubleExceptionVector_text,
.DoubleExceptionVector.text,
DOUBLEEXC_VECTOR_VADDR,
- 40,
+ 48,
.DoubleExceptionVector.literal)
. = (LOADADDR( .DoubleExceptionVector.text ) + SIZEOF( .DoubleExceptionVector.text ) + 3) & ~ 3;