From fd3d2742d558d33560ec5dfee3001e561b5c0822 Mon Sep 17 00:00:00 2001 From: Gerald Schaefer Date: Sun, 3 Feb 2019 21:36:46 +0100 Subject: [PATCH] s390/kprobes: use static buffer for insn_page With a relocatable kernel that could reside at any place in memory, the current logic for allocating a kprobes insn_page does not work. The GFP_DMA allocated buffer might be more than 2 GB away from the kernel. Use a static buffer for the insn_page instead. Signed-off-by: Gerald Schaefer Reviewed-by: Philipp Rudo Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/kprobes.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-) diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index 7c0a095e9c5f..263426dcf97d 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -27,29 +27,30 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); struct kretprobe_blackpoint kretprobe_blacklist[] = { }; -DEFINE_INSN_CACHE_OPS(dmainsn); +DEFINE_INSN_CACHE_OPS(s390_insn); -static void *alloc_dmainsn_page(void) +static int insn_page_in_use; +static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE); + +static void *alloc_s390_insn_page(void) { - void *page; - - page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA); - if (page) - set_memory_x((unsigned long) page, 1); - return page; + if (xchg(&insn_page_in_use, 1) == 1) + return NULL; + set_memory_x((unsigned long) &insn_page, 1); + return &insn_page; } -static void free_dmainsn_page(void *page) +static void free_s390_insn_page(void *page) { set_memory_nx((unsigned long) page, 1); - free_page((unsigned long)page); + xchg(&insn_page_in_use, 0); } -struct kprobe_insn_cache kprobe_dmainsn_slots = { - .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex), - .alloc = alloc_dmainsn_page, - .free = free_dmainsn_page, - .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages), +struct kprobe_insn_cache kprobe_s390_insn_slots = { + .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex), + .alloc = alloc_s390_insn_page, + .free = free_s390_insn_page, + .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages), .insn_size = MAX_INSN_SIZE, }; @@ -102,7 +103,7 @@ static int s390_get_insn_slot(struct kprobe *p) */ p->ainsn.insn = NULL; if (is_kernel_addr(p->addr)) - p->ainsn.insn = get_dmainsn_slot(); + p->ainsn.insn = get_s390_insn_slot(); else if (is_module_addr(p->addr)) p->ainsn.insn = get_insn_slot(); return p->ainsn.insn ? 0 : -ENOMEM; @@ -114,7 +115,7 @@ static void s390_free_insn_slot(struct kprobe *p) if (!p->ainsn.insn) return; if (is_kernel_addr(p->addr)) - free_dmainsn_slot(p->ainsn.insn, 0); + free_s390_insn_slot(p->ainsn.insn, 0); else free_insn_slot(p->ainsn.insn, 0); p->ainsn.insn = NULL;