From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id C961CB6F81 for ; Wed, 15 Jun 2011 02:58:05 +1000 (EST) Date: Tue, 14 Jun 2011 12:58:02 -0400 From: Steve Best To: Steve Best , linuxppc-dev@lists.ozlabs.org Message-Id: <20110614165011.23034.66685.sendpatchset@squad5-lp1.lab.bos.redhat.com> Subject: [PATCH] powerpc/mm: add devmem_is_allowed() for STRICT_DEVMEM checking Cc: Steve Best List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Provide devmem_is_allowed() routine to restrict access to kernel memory from userspace. Set CONFIG_STRICT_DEVMEM config option to switch on checking. Signed-off-by: Steve Best diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug index e72dcf6..e1aab6b 100644 --- a/arch/powerpc/Kconfig.debug +++ b/arch/powerpc/Kconfig.debug @@ -283,4 +283,15 @@ config PPC_EARLY_DEBUG_CPM_ADDR platform probing is done, all platforms selected must share the same address. +config STRICT_DEVMEM + def_bool y + prompt "Filter access to /dev/mem" + ---help--- + This option restricts access to /dev/mem. If this option is + disabled, you allow userspace access to all memory, including + kernel and userspace memory. + Memory access is required for experts who want to debug the kernel. + + If you are unsure, say Y. + endmenu diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index 2cd664e..dc2ec96 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -261,6 +261,7 @@ extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg); extern void copy_user_page(void *to, void *from, unsigned long vaddr, struct page *p); extern int page_is_ram(unsigned long pfn); +extern int devmem_is_allowed(unsigned long pfn); #ifdef CONFIG_PPC_SMLPAR void arch_free_page(struct page *page, int order); diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 29d4dde..b1a6233 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -520,3 +520,21 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, hash_preload(vma->vm_mm, address, access, trap); #endif /* CONFIG_PPC_STD_MMU */ } + +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * On PowerPC, access has to be given to data regions used by X. We have to + * disallow access to device-exclusive MMIO regions and system RAM. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if ((pfn >= 57360 || pfn <= 57392)) + return 1; + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +}