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    Subject[v2 1/5] arm64: kdump: reserve memory for crash dump kernel
    Date
    On system kernel, the memory region used by crash dump kernel must be
    specified by "crashkernel=X@Y" boot parameter. reserve_crashkernel()
    will allocate the region in "System RAM" and reserve it for later use.

    On crash dump kernel, memory region information in system kernel is
    described in a specific region specified by "elfcorehdr=X@Y" boot parameter.
    reserve_elfcorehdr() will set aside the region to avoid data destruction
    by the kernel.

    Crash dump kernel will access memory regions in system kernel via
    copy_oldmem_page(), which reads a page by ioremap'ing it assuming that
    such pages are not part of main memory of crash dump kernel.
    This is true under non-UEFI environment because kexec-tools modifies
    a device tree adding "usablemem" attributes to memory sections.
    Under UEFI, however, this is not true because UEFI remove memory sections
    in a device tree and export all the memory regions, even though they belong
    to system kernel.

    So we should add "mem=X[MG]" boot parameter to limit the memory size and
    avoid hitting the following assertion in ioremap():
    if (WARN_ON(pfn_valid(__phys_to_pfn(phys_addr))))
    return NULL;

    Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    ---
    arch/arm64/kernel/Makefile | 1 +
    arch/arm64/kernel/crash_dump.c | 71 +++++++++++++++++++++++++++++++++
    arch/arm64/kernel/setup.c | 8 +++-
    arch/arm64/mm/init.c | 84 ++++++++++++++++++++++++++++++++++++++++
    4 files changed, 163 insertions(+), 1 deletion(-)
    create mode 100644 arch/arm64/kernel/crash_dump.c

    diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
    index ac3c2e2..6fcc602 100644
    --- a/arch/arm64/kernel/Makefile
    +++ b/arch/arm64/kernel/Makefile
    @@ -36,6 +36,7 @@ arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o
    arm64-obj-$(CONFIG_PCI) += pci.o
    arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o
    arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
    +arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o

    obj-y += $(arm64-obj-y) vdso/
    obj-m += $(arm64-obj-m)
    diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c
    new file mode 100644
    index 0000000..3d86c0a
    --- /dev/null
    +++ b/arch/arm64/kernel/crash_dump.c
    @@ -0,0 +1,71 @@
    +/*
    + * Routines for doing kexec-based kdump
    + *
    + * Copyright (C) 2014 Linaro Limited
    + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License version 2 as
    + * published by the Free Software Foundation.
    + */
    +
    +#include <linux/crash_dump.h>
    +#include <linux/errno.h>
    +#include <linux/io.h>
    +#include <linux/memblock.h>
    +#include <linux/uaccess.h>
    +#include <asm/memory.h>
    +
    +/**
    + * copy_oldmem_page() - copy one page from old kernel memory
    + * @pfn: page frame number to be copied
    + * @buf: buffer where the copied page is placed
    + * @csize: number of bytes to copy
    + * @offset: offset in bytes into the page
    + * @userbuf: if set, @buf is in a user address space
    + *
    + * This function copies one page from old kernel memory into buffer pointed by
    + * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
    + * copied or negative error in case of failure.
    + */
    +ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
    + size_t csize, unsigned long offset,
    + int userbuf)
    +{
    + void *vaddr;
    +
    + if (!csize)
    + return 0;
    +
    + vaddr = ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
    + if (!vaddr)
    + return -ENOMEM;
    +
    + if (userbuf) {
    + if (copy_to_user(buf, vaddr + offset, csize)) {
    + iounmap(vaddr);
    + return -EFAULT;
    + }
    + } else {
    + memcpy(buf, vaddr + offset, csize);
    + }
    +
    + iounmap(vaddr);
    +
    + return csize;
    +}
    +
    +/**
    + * elfcorehdr_read - read from ELF core header
    + * @buf: buffer where the data is placed
    + * @csize: number of bytes to read
    + * @ppos: address in the memory
    + *
    + * This function reads @count bytes from elf core header which exists
    + * on crash dump kernel's memory.
    + */
    +ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
    +{
    + memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
    + return count;
    +}
    diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
    index 51ef972..7932bd0 100644
    --- a/arch/arm64/kernel/setup.c
    +++ b/arch/arm64/kernel/setup.c
    @@ -31,7 +31,6 @@
    #include <linux/screen_info.h>
    #include <linux/init.h>
    #include <linux/kexec.h>
    -#include <linux/crash_dump.h>
    #include <linux/root_dev.h>
    #include <linux/clk-provider.h>
    #include <linux/cpu.h>
    @@ -364,6 +363,12 @@ static void __init request_standard_resources(void)
    kernel_data.end <= res->end)
    request_resource(res, &kernel_data);
    }
    +
    +#ifdef CONFIG_KEXEC
    + /* User space tools will detect the region with /proc/iomem */
    + if (crashk_res.end)
    + insert_resource(&iomem_resource, &crashk_res);
    +#endif
    }

    u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
    @@ -393,6 +398,7 @@ void __init setup_arch(char **cmdline_p)
    local_async_enable();

    efi_init();
    +
    arm64_memblock_init();

    paging_init();
    diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
    index ae85da6..ea70d41 100644
    --- a/arch/arm64/mm/init.c
    +++ b/arch/arm64/mm/init.c
    @@ -34,6 +34,8 @@
    #include <linux/dma-contiguous.h>
    #include <linux/efi.h>
    #include <linux/swiotlb.h>
    +#include <linux/kexec.h>
    +#include <linux/crash_dump.h>

    #include <asm/fixmap.h>
    #include <asm/memory.h>
    @@ -66,6 +68,81 @@ static int __init early_initrd(char *p)
    early_param("initrd", early_initrd);
    #endif

    +#ifdef CONFIG_KEXEC
    +/*
    + * reserve_crashkernel() - reserves memory for crash kernel
    + *
    + * This function reserves memory area given in "crashkernel=" kernel command
    + * line parameter. The memory reserved is used by a dump capture kernel when
    + * primary kernel is crashing.
    + */
    +static void __init reserve_crashkernel(phys_addr_t limit)
    +{
    + unsigned long long crash_size = 0, crash_base = 0;
    + int ret;
    +
    + ret = parse_crashkernel(boot_command_line, limit,
    + &crash_size, &crash_base);
    + if (ret)
    + return;
    +
    + if (crash_base == 0) {
    + crash_base = memblock_alloc(crash_size, 1 << 20);
    + if (crash_base == 0) {
    + pr_warn("crashkernel allocation failed (size:%llx)\n",
    + crash_size);
    + return;
    + }
    + } else {
    + /* User specifies base address explicitly. Sanity check */
    + if (!memblock_is_region_memory(crash_base, crash_size) ||
    + memblock_is_region_reserved(crash_base, crash_size)) {
    + pr_warn("crashkernel= has wrong address or size\n");
    + return;
    + }
    +
    + if (memblock_reserve(crash_base, crash_size)) {
    + pr_warn("crashkernel reservation failed - out of memory\n");
    + return;
    + }
    + }
    +
    + pr_info("Reserving %lldMB of memory at %lldMB for crashkernel\n",
    + crash_size >> 20, crash_base >> 20);
    +
    + crashk_res.start = crash_base;
    + crashk_res.end = crash_base + crash_size - 1;
    +}
    +#endif /* CONFIG_KEXEC */
    +
    +#ifdef CONFIG_CRASH_DUMP
    +/*
    + * reserve_elfcorehdr() - reserves memory for elf core header
    + *
    + * This function reserves memory area given in "elfcorehdr=" kernel command
    + * line parameter. The memory reserved is used by a dump capture kernel to
    + * identify the memory used by primary kernel.
    + */
    +static void __init reserve_elfcorehdr(void)
    +{
    + if (!elfcorehdr_size)
    + return;
    +
    + if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
    + pr_warn("elfcorehdr reservation failed - memory is in use (0x%llx)\n",
    + elfcorehdr_addr);
    + return;
    + }
    +
    + if (memblock_reserve(elfcorehdr_addr, elfcorehdr_size)) {
    + pr_warn("elfcorehdr reservation failed - out of memory\n");
    + return;
    + }
    +
    + pr_info("Reserving %lldKB of memory at %lldMB for elfcorehdr\n",
    + elfcorehdr_size >> 10, elfcorehdr_addr >> 20);
    +}
    +#endif /* CONFIG_CRASH_DUMP */
    /*
    * Return the maximum physical address for ZONE_DMA (DMA_BIT_MASK(32)). It
    * currently assumes that for memory starting above 4G, 32-bit devices will
    @@ -170,6 +247,13 @@ void __init arm64_memblock_init(void)
    memblock_reserve(__virt_to_phys(initrd_start), initrd_end - initrd_start);
    #endif

    +#ifdef CONFIG_KEXEC
    + reserve_crashkernel(memory_limit);
    +#endif
    +#ifdef CONFIG_CRASH_DUMP
    + reserve_elfcorehdr();
    +#endif
    +
    early_init_fdt_scan_reserved_mem();

    /* 4GB maximum for 32-bit only capable devices */
    --
    1.7.9.5


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