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/kernel/dumpstack.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/s390/kernel/dumpstack.c') diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c index 5b23c4f6e50c..301b945de77b 100644 --- a/arch/s390/kernel/dumpstack.c +++ b/arch/s390/kernel/dumpstack.c @@ -77,11 +77,11 @@ void dump_trace(dump_trace_func_t func, void *data, struct task_struct *task, frame_size = STACK_FRAME_OVERHEAD + sizeof(struct pt_regs); #ifdef CONFIG_CHECK_STACK sp = __dump_trace(func, data, sp, - S390_lowcore.panic_stack + frame_size - PAGE_SIZE, - S390_lowcore.panic_stack + frame_size); + S390_lowcore.nodat_stack + frame_size - STACK_SIZE, + S390_lowcore.nodat_stack + frame_size); #endif sp = __dump_trace(func, data, sp, - S390_lowcore.async_stack + frame_size - ASYNC_SIZE, + S390_lowcore.async_stack + frame_size - STACK_SIZE, S390_lowcore.async_stack + frame_size); task = task ?: current; __dump_trace(func, data, sp, -- cgit v1.2.3