arm64: kdump: provide /proc/vmcore file
Arch-specific functions are added to allow for implementing a crash dump file interface, /proc/vmcore, which can be viewed as a ELF file. A user space tool, like kexec-tools, is responsible for allocating a separate region for the core's ELF header within crash kdump kernel memory and filling it in when executing kexec_load(). Then, its location will be advertised to crash dump kernel via a new device-tree property, "linux,elfcorehdr", and crash dump kernel preserves the region for later use with reserve_elfcorehdr() at boot time. On crash dump kernel, /proc/vmcore will access the primary kernel's memory with copy_oldmem_page(), which feeds the data page-by-page by ioremap'ing it since it does not reside in linear mapping on crash dump kernel. Meanwhile, elfcorehdr_read() is simple as the region is always mapped. Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Reviewed-by: James Morse <james.morse@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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@ -736,6 +736,17 @@ config KEXEC
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but it is independent of the system firmware. And like a reboot
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you can start any kernel with it, not just Linux.
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config CRASH_DUMP
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bool "Build kdump crash kernel"
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help
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Generate crash dump after being started by kexec. This should
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be normally only set in special crash dump kernels which are
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loaded in the main kernel with kexec-tools into a specially
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reserved region and then later executed after a crash by
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kdump/kexec.
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For more details see Documentation/kdump/kdump.txt
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config XEN_DOM0
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def_bool y
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depends on XEN
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@ -52,6 +52,7 @@ arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \
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cpu-reset.o
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arm64-obj-$(CONFIG_ARM64_RELOC_TEST) += arm64-reloc-test.o
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arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o
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arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
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obj-y += $(arm64-obj-y) vdso/ probes/
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obj-m += $(arm64-obj-m)
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71
arch/arm64/kernel/crash_dump.c
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71
arch/arm64/kernel/crash_dump.c
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@ -0,0 +1,71 @@
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/*
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* Routines for doing kexec-based kdump
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*
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* Copyright (C) 2017 Linaro Limited
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* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/crash_dump.h>
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#include <linux/errno.h>
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#include <linux/io.h>
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#include <linux/memblock.h>
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#include <linux/uaccess.h>
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#include <asm/memory.h>
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/**
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* copy_oldmem_page() - copy one page from old kernel memory
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* @pfn: page frame number to be copied
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* @buf: buffer where the copied page is placed
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* @csize: number of bytes to copy
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* @offset: offset in bytes into the page
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* @userbuf: if set, @buf is in a user address space
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*
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* This function copies one page from old kernel memory into buffer pointed by
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* @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
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* copied or negative error in case of failure.
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*/
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ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
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size_t csize, unsigned long offset,
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int userbuf)
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{
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void *vaddr;
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if (!csize)
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return 0;
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vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
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if (!vaddr)
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return -ENOMEM;
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if (userbuf) {
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if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
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memunmap(vaddr);
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return -EFAULT;
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}
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} else {
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memcpy(buf, vaddr + offset, csize);
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}
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memunmap(vaddr);
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return csize;
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}
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/**
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* elfcorehdr_read - read from ELF core header
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* @buf: buffer where the data is placed
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* @csize: number of bytes to read
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* @ppos: address in the memory
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*
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* This function reads @count bytes from elf core header which exists
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* on crash dump kernel's memory.
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*/
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ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
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{
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memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
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return count;
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}
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@ -39,6 +39,7 @@
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/kexec.h>
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#include <linux/crash_dump.h>
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#include <asm/boot.h>
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#include <asm/fixmap.h>
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@ -165,6 +166,56 @@ static void __init kexec_reserve_crashkres_pages(void)
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}
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#endif /* CONFIG_KEXEC_CORE */
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#ifdef CONFIG_CRASH_DUMP
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static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
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const char *uname, int depth, void *data)
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{
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const __be32 *reg;
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int len;
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if (depth != 1 || strcmp(uname, "chosen") != 0)
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return 0;
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reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
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if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
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return 1;
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elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, ®);
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elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, ®);
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return 1;
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}
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/*
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* reserve_elfcorehdr() - reserves memory for elf core header
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*
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* This function reserves the memory occupied by an elf core header
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* described in the device tree. This region contains all the
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* information about primary kernel's core image and is used by a dump
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* capture kernel to access the system memory on primary kernel.
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*/
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static void __init reserve_elfcorehdr(void)
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{
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of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL);
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if (!elfcorehdr_size)
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return;
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if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
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pr_warn("elfcorehdr is overlapped\n");
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return;
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}
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memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
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pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n",
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elfcorehdr_size >> 10, elfcorehdr_addr);
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}
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#else
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static void __init reserve_elfcorehdr(void)
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{
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}
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#endif /* CONFIG_CRASH_DUMP */
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/*
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* Return the maximum physical address for ZONE_DMA (DMA_BIT_MASK(32)). It
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* currently assumes that for memory starting above 4G, 32-bit devices will
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@ -423,6 +474,8 @@ void __init arm64_memblock_init(void)
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reserve_crashkernel();
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reserve_elfcorehdr();
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dma_contiguous_reserve(arm64_dma_phys_limit);
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memblock_allow_resize();
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