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xtensa: don't allow overflow/underflow on unaligned stack

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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>
This commit is contained in:
Max Filippov 2014-08-07 01:03:01 +04:00
parent d1b6ba82a5
commit 3cfc096e4c
3 changed files with 10 additions and 7 deletions
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5
arch/xtensa/kernel/traps.c
View File

@ -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)

8
arch/xtensa/kernel/vectors.S
View File

@ -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

4
arch/xtensa/kernel/vmlinux.lds.S
View File

@ -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;