On 9 August 2016 at 03:56, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote: > On crash dump kernel, all the information about primary kernel's system > memory (core image) is available in elf core header. > The primary kernel will set aside this header with reserve_elfcorehdr() > at boot time and inform crash dump kernel of its location via a new > device-tree property, "linux,elfcorehdr". > > Please note that all other architectures use traditional "elfcorehdr=" > kernel parameter for this purpose. > > Then crash dump kernel will access the primary kernel's memory with > copy_oldmem_page(), which reads one page by ioremap'ing it since it does > not reside in linear mapping on crash dump kernel. > > We also need our own elfcorehdr_read() here since the header is placed > within crash dump kernel's usable memory. > > Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org> > --- > arch/arm64/Kconfig | 11 +++++++ > arch/arm64/kernel/Makefile | 1 + > arch/arm64/kernel/crash_dump.c | 71 ++++++++++++++++++++++++++++++++++++++++++ > arch/arm64/mm/init.c | 54 ++++++++++++++++++++++++++++++++ > 4 files changed, 137 insertions(+) > create mode 100644 arch/arm64/kernel/crash_dump.c > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 69c8787..9ede54b 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -682,6 +682,17 @@ config KEXEC > but it is independent of the system firmware. And like a reboot > you can start any kernel with it, not just Linux. > > +config CRASH_DUMP > + bool "Build kdump crash kernel" > + help > + Generate crash dump after being started by kexec. This should > + be normally only set in special crash dump kernels which are > + loaded in the main kernel with kexec-tools into a specially > + reserved region and then later executed after a crash by > + kdump/kexec. > + > + For more details see Documentation/kdump/kdump.txt > + > config XEN_DOM0 > def_bool y > depends on XEN > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index 14f7b65..f1cbfc8 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -48,6 +48,7 @@ arm64-obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o > arm64-obj-$(CONFIG_HIBERNATION) += hibernate.o hibernate-asm.o > arm64-obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o \ > cpu-reset.o > +arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o > > obj-y += $(arm64-obj-y) vdso/ probes/ > 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..2dc54d1 > --- /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 at 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_to_phys(pfn), PAGE_SIZE); Could we please use memremap() here? > + 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); ... and memunmap here? ioremap_cache() is not very well defined, and memremap() has been introduced specifically to replace it, so I think we should use it in new code. Thanks, Ard. > + > + 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/mm/init.c b/arch/arm64/mm/init.c > index e3771c4..bba1e39 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -36,6 +36,7 @@ > #include <linux/efi.h> > #include <linux/swiotlb.h> > #include <linux/kexec.h> > +#include <linux/crash_dump.h> > > #include <asm/boot.h> > #include <asm/fixmap.h> > @@ -186,6 +187,57 @@ static void __init reserve_crashkernel(void) > } > #endif /* CONFIG_KEXEC_CORE */ > > +#ifdef CONFIG_CRASH_DUMP > +static int __init early_init_dt_scan_elfcorehdr(unsigned long node, > + const char *uname, int depth, void *data) > +{ > + const __be32 *reg; > + int len; > + > + if (depth != 1 || strcmp(uname, "chosen") != 0) > + return 0; > + > + reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len); > + if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells))) > + return 1; > + > + elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, ®); > + elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, ®); > + > + return 1; > +} > + > +/* > + * reserve_elfcorehdr() - reserves memory for elf core header > + * > + * This function reserves elf core header given in "elfcorehdr=" kernel > + * command line parameter. This region contains all the information about > + * primary kernel's core image and is used by a dump capture kernel to > + * access the system memory on primary kernel. > + */ > +static void __init reserve_elfcorehdr(void) > +{ > + of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL); > + > + if (!elfcorehdr_size) > + return; > + > + if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) { > + pr_warn("elfcorehdr is overlapped\n"); > + return; > + } > + > + memblock_reserve(elfcorehdr_addr, elfcorehdr_size); > + > + pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n", > + elfcorehdr_size >> 10, elfcorehdr_addr); > +} > +#else > +static void __init reserve_elfcorehdr(void) > +{ > + ; > +} > +#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 > @@ -444,6 +496,8 @@ void __init arm64_memblock_init(void) > > reserve_crashkernel(); > > + reserve_elfcorehdr(); > + > dma_contiguous_reserve(arm64_dma_phys_limit); > > memblock_allow_resize(); > -- > 2.9.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel