Re: [PATCH 1/5] arm64: kdump: reserve memory for crash dump kernel
From: AKASHI Takahiro
Date: Sun Mar 29 2015 - 22:36:14 EST
Thank you, Geoff.
On 03/27/2015 01:43 PM, Geoff Levand wrote:
Hi Takahiro,
On Thu, 2015-03-26 at 17:28 +0900, AKASHI Takahiro wrote:
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 with ioremap'ing it assuming that
s/page with/page by/
Fix it.
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 meory size and
s/meory/memory/
Fix it.
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@xxxxxxxxxx>
---
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/crash_dump.c | 71 ++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/setup.c | 78 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 150 insertions(+)
create mode 100644 arch/arm64/kernel/crash_dump.c
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index da9a7ee..3c24d4e 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..dd31b2e
--- /dev/null
+++ b/arch/arm64/kernel/crash_dump.c
@@ -0,0 +1,71 @@
+/*
+ * arch/arm64/kernel/crash_dump.c
I would recommend against adding paths in source files. It often
happens that files with paths are moved, but the file comments are not
updated.
Yeah, will fix it.
+ *
+ * Copyright (C) 2014 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
+ *
+ * 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 int he user address space
s/is int he user/is a user/
Fix it. Sorry for bunch of typos.
+ *
+ * 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)
Since userbuf is a binary flag, I think type bool would be better.
Change the comments from 'set' and '1' to 'true'.
Should offset be type size_t?
No. The prototype is already there in include/linux/crash_dump.h.
+{
+ void *vaddr;
+
+ if (!csize)
+ return 0;
+
+ vaddr = ioremap(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)
Should ppos be type phys_addr_t *?
No. The prototype is already there in include/linux/crash_dump.h.
+{
+ 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 e8420f6..daaed93 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -323,6 +323,69 @@ static void __init setup_machine_fdt(phys_addr_t dt_phys)
dump_stack_set_arch_desc("%s (DT)", of_flat_dt_get_machine_name());
}
+#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(void)
+{
+ unsigned long long crash_size, crash_base;
+ int ret;
+
+ /* use ULONG_MAX since we don't know system memory size here. */
+ ret = parse_crashkernel(boot_command_line, ULONG_MAX,
+ &crash_size, &crash_base);
+ if (ret)
+ return;
+
+ ret = memblock_reserve(crash_base, crash_size);
+ if (ret < 0) {
+ pr_warn("crashkernel reservation failed - memory is in use (0x%lx)\n",
+ (unsigned long)crash_base);
Can we use 0x%llx here and below and avoid these casts?
Fix it.
+ return;
+ }
+
+ pr_info("Reserving %ldMB of memory at %ldMB for crashkernel\n",
+ (unsigned long)(crash_size >> 20),
+ (unsigned long)(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)
+{
+ int ret;
+
+ if (!elfcorehdr_size)
+ return;
+
+ ret = memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
+ if (ret < 0) {
+ pr_warn("elfcorehdr reservation failed - memory is in use (0x%lx)\n",
+ (unsigned long)elfcorehdr_addr);
+ return;
+ }
+
+ pr_info("Reserving %ldKB of memory at %ldMB for elfcorehdr\n",
+ (unsigned long)(elfcorehdr_size >> 10),
+ (unsigned long)(elfcorehdr_addr >> 20));
+}
+#endif /* CONFIG_CRASH_DUMP */
+
static void __init request_standard_resources(void)
{
struct memblock_region *region;
@@ -378,10 +441,25 @@ void __init setup_arch(char **cmdline_p)
local_async_enable();
efi_init();
Maybe have a blank line here?
Add one.
+ /*
+ * reserve_crashkernel() and reserver_elfcorehdr() must be called
s/reserver_elfcorehdr/reserve_elfcorehdr/
+ * before arm64_bootmem_init() because dma_contiguous_reserve()
+ * may conflict with those regions.
+ */
+#ifdef CONFIG_KEXEC
+ reserve_crashkernel();
+#endif
+#ifdef CONFIG_CRASH_DUMP
+ reserve_elfcorehdr();
+#endif
arm64_memblock_init();
paging_init();
request_standard_resources();
+#ifdef CONFIG_KEXEC
+ /* kexec-tool will detect the region with /proc/iomem */
There are more kexec user programs than kexec-tools, so I think
something like 'user space tools' would be better.
Sure, fix it.
-Takahiro AKASHI
+ insert_resource(&iomem_resource, &crashk_res);
+#endif
early_ioremap_reset();
--
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