| Message ID | 1429861989-8417-2-git-send-email-takahiro.akashi@linaro.org |
|---|---|
| State | New |
| Headers | show |
Hi Baoquan, On 04/28/2015 06:19 PM, Baoquan He wrote: >> +#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. >> + */ > > Hi AKASHI, > > May I know why elfcorehdr need be reserved separately but not locate a > memory region in crashkernel reserved region like all other ARCHs? Is > there any special reason? I don't get your point, but arm as well as arm64 locates elfcorehdr in a crash kernel's memory region. See kexec/arch/arm{,64}/crashdump-arm{,64}.c in kexec-tools. And this region is reserved at boot time *on crash kernel* because we don't want to corrupt it accidentally. (After Mark's comment, we might better remove the mmu mapping for this region, too.) Make sense? -Takahiro AKASHI > Thanks > Baoquan > >> +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 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 05/11/2015 04:54 PM, Baoquan He wrote: > On 05/11/15 at 04:38pm, AKASHI Takahiro wrote: >> Hi Baoquan, >> >> On 04/28/2015 06:19 PM, Baoquan He wrote: >>>> +#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. >>>> + */ >>> >>> Hi AKASHI, >>> >>> May I know why elfcorehdr need be reserved separately but not locate a >>> memory region in crashkernel reserved region like all other ARCHs? Is >>> there any special reason? >> >> I don't get your point, but arm as well as arm64 locates elfcorehdr >> in a crash kernel's memory region. >> See kexec/arch/arm{,64}/crashdump-arm{,64}.c in kexec-tools. >> >> And this region is reserved at boot time *on crash kernel* because we don't want >> to corrupt it accidentally. >> (After Mark's comment, we might better remove the mmu mapping for this region, too.) > > > Sorry, I don't make myself clear. > > In this patch you reserve a separate memory region in 1st kernel to > store elfcorehdr. I am wondering why you don't call add_buffer in > kexec-tools directly. Like this you can get a region from reserved > crashkernel region. Then you don't need reserve_elfcorehdr() to reserve > memory for elfcorehdr specifically. Like other ARCHs do only one memory > region is reserved in 1st kernel, that's crashkernel region. I think that you misunderstand somewhat. * Kexec-tools only locates/identifies a small region for elfcore header within crash kernel's memory region while 1st kernel is running. * the data in elfcore header is filled up by kexec_load system call on 1st kernel. * 1st kernel doesn't reserve any region for elfcore header because the kernel commandline parameters don't contains "elfcorehdr=" parameter, then elfcorehdr_size=0. * Crash dump kernel does reserve the region, as I said, because we don't want to corrupt the info in elfcore header accidentally while crash kernel is running. Clear? -Takahiro AKASHI > Thanks > Baoquan >> >> >> Make sense? >> >> -Takahiro AKASHI >> >>> Thanks >>> Baoquan >>> >>>> +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 >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 05/11/2015 06:41 PM, Baoquan He wrote: > On 05/11/15 at 05:17pm, AKASHI Takahiro wrote: >> On 05/11/2015 04:54 PM, Baoquan He wrote: >>> In this patch you reserve a separate memory region in 1st kernel to >>> store elfcorehdr. I am wondering why you don't call add_buffer in >>> kexec-tools directly. Like this you can get a region from reserved >>> crashkernel region. Then you don't need reserve_elfcorehdr() to reserve >>> memory for elfcorehdr specifically. Like other ARCHs do only one memory >>> region is reserved in 1st kernel, that's crashkernel region. >> >> I think that you misunderstand somewhat. >> * Kexec-tools only locates/identifies a small region for elfcore header within crash kernel's >> memory region while 1st kernel is running. >> * the data in elfcore header is filled up by kexec_load system call on 1st kernel. >> * 1st kernel doesn't reserve any region for elfcore header because the kernel >> commandline parameters don't contains "elfcorehdr=" parameter, then elfcorehdr_size=0. >> * Crash dump kernel does reserve the region, as I said, because we don't want to >> corrupt the info in elfcore header accidentally while crash kernel is running. >> >> Clear? > > OK, got it now. > > Then I am wondering why "elfcorehdr=" can't be contained in kernel > cmdline as other ARCH does. Maybe I need go over all related threads > then know why it is. Thanks for explanation. Kexec-tools on 1st kernel appends "elfcorehdr=" to the kernel command line, actually chosen/bootargs in a device tree, that is passed to *crash dump kernel*. So when crash dump kernel boots up, it can recognizes that area (and reserves it for later use of managing /proc/vmcore.) Thanks, -Takahiro AKASHI > Thanks > Baoquan > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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 */
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