From ce3dc447493ff4186b192b38d723ab5e8c1eb52f Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 12 Sep 2017 16:37:33 +0200 Subject: s390: add support for virtually mapped kernel stacks With virtually mapped kernel stacks the kernel stack overflow detection is now fault based, every stack has a guard page in the vmalloc space. The panic_stack is renamed to nodat_stack and is used for all function that need to run without DAT, e.g. memcpy_real or do_start_kdump. The main effect is a reduction in the kernel image size as with vmap stacks the old style overflow checking that adds two instructions per function is not needed anymore. Result from bloat-o-meter: add/remove: 20/1 grow/shrink: 13/26854 up/down: 2198/-216240 (-214042) In regard to performance the micro-benchmark for fork has a hit of a few microseconds, allocating 4 pages in vmalloc space is more expensive compare to an order-2 page allocation. But with real workload I could not find a noticeable difference. Acked-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/include/asm/processor.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/s390/include/asm/processor.h') diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h index 43494a014d5b..3c1e723a143a 100644 --- a/arch/s390/include/asm/processor.h +++ b/arch/s390/include/asm/processor.h @@ -162,6 +162,14 @@ struct thread_struct { typedef struct thread_struct thread_struct; +/* + * General size of a stack + */ +#define STACK_ORDER 2 +#define STACK_SIZE (PAGE_SIZE << STACK_ORDER) +#define STACK_INIT_OFFSET \ + (STACK_SIZE - STACK_FRAME_OVERHEAD - sizeof(struct pt_regs)) + /* * Stack layout of a C stack frame. */ -- cgit v1.2.3-59-g8ed1b