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e62aaeac42
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>
72 lines
1.8 KiB
C
72 lines
1.8 KiB
C
/*
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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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