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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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