Re: [PATCH 1/5] arm64: kdump: reserve memory for crash dump kernel

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@linaro.org

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@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 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();