Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755308AbaAVL2w (ORCPT ); Wed, 22 Jan 2014 06:28:52 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:44543 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753613AbaAVL2n (ORCPT ); Wed, 22 Jan 2014 06:28:43 -0500 From: Wang Nan To: CC: Eric Biederman , Russell King , Andrew Morton , Geng Hui , , , , Wang Nan , Subject: [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem Date: Wed, 22 Jan 2014 19:25:16 +0800 Message-ID: <1390389916-8711-4-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.4 In-Reply-To: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> References: <1390389916-8711-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.247] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch allows the kernel to be loaded at the middle of kernel awared physical memory. Before this patch, users must use mem= or device tree to cheat kernel about the start address of physical memory. This feature is useful in some special cases, for example, building a crash dump kernel. Without it, kernel command line, atag and devicetree must be adjusted carefully, sometimes is impossible. Signed-off-by: Wang Nan Cc: # 3.4+ Cc: Eric Biederman Cc: Russell King Cc: Andrew Morton Cc: Geng Hui --- arch/arm/mm/init.c | 21 ++++++++++++++++++++- arch/arm/mm/mmu.c | 13 +++++++++++++ mm/page_alloc.c | 7 +++++-- 3 files changed, 38 insertions(+), 3 deletions(-) diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index 3e8f106..4952726 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c @@ -334,9 +334,28 @@ void __init arm_memblock_init(struct meminfo *mi, { int i; - for (i = 0; i < mi->nr_banks; i++) + for (i = 0; i < mi->nr_banks; i++) { memblock_add(mi->bank[i].start, mi->bank[i].size); + /* + * In some special case, for example, building a crushdump + * kernel, we want the kernel to be loaded in the middle of + * physical memory. In such case, the physical memory before + * PHYS_OFFSET is awkward: it can't get directly mapped + * (because its address will be smaller than PAGE_OFFSET, + * disturbs user address space) also can't be mapped as + * HighMem. We reserve such pages here. The only way to access + * those pages is ioremap. + */ + if (mi->bank[i].start < PHYS_OFFSET) { + unsigned long reserv_size = PHYS_OFFSET - + mi->bank[i].start; + if (reserv_size > mi->bank[i].size) + reserv_size = mi->bank[i].size; + memblock_reserve(mi->bank[i].start, reserv_size); + } + } + /* Register the kernel text, kernel data and initrd with memblock. */ #ifdef CONFIG_XIP_KERNEL memblock_reserve(__pa(_sdata), _end - _sdata); diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 580ef2d..2a17c24 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -1308,6 +1308,19 @@ static void __init map_lowmem(void) if (start >= end) break; + /* + * If this memblock contain memory before PAGE_OFFSET, memory + * before PAGE_OFFSET should't get directly mapped, see code + * in create_mapping(). However, memory after PAGE_OFFSET is + * occupyed by kernel and still need to be mapped. + */ + if (__phys_to_virt(start) < PAGE_OFFSET) { + if (__phys_to_virt(end) > PAGE_OFFSET) + start = __virt_to_phys(PAGE_OFFSET); + else + break; + } + map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = end - start; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5248fe0..d2959e3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4840,10 +4840,13 @@ static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat) */ if (pgdat == NODE_DATA(0)) { mem_map = NODE_DATA(0)->node_mem_map; -#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP + /* + * In case of CONFIG_HAVE_MEMBLOCK_NODE_MAP or when kernel + * loaded at the middle of physical memory, mem_map should + * be adjusted. + */ if (page_to_pfn(mem_map) != pgdat->node_start_pfn) mem_map -= (pgdat->node_start_pfn - ARCH_PFN_OFFSET); -#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */ } #endif #endif /* CONFIG_FLAT_NODE_MEM_MAP */ -- 1.8.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/