From 3cfc096e4c4fbc234634cf8a30d40348a25fc9ba Mon Sep 17 00:00:00 2001 From: Max Filippov Date: Thu, 7 Aug 2014 01:03:01 +0400 Subject: [PATCH] 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 --- arch/xtensa/kernel/traps.c | 5 +---- arch/xtensa/kernel/vectors.S | 8 +++++++- arch/xtensa/kernel/vmlinux.lds.S | 4 ++-- 3 files changed, 10 insertions(+), 7 deletions(-) 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 @@ static dispatch_init_table_t __initdata dispatch_init_table[] = { #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 @@ do_illegal_instruction(struct pt_regs *regs) */ #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 @@ do_unaligned_user (struct pt_regs *regs) } #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 @@ _DoubleExceptionVector_WindowOverflow: 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 @@ SECTIONS .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; -- 2.7.4