在 2019年01月11日 22:56, Borislav Petkov 写道: > On Thu, Jan 10, 2019 at 08:19:43PM +0800, Lianbo Jiang wrote: >> This document lists some variables that export to vmcoreinfo, and briefly >> describles what these variables indicate. It should be instructive for >> many people who do not know the vmcoreinfo. >> >> Suggested-by: Borislav Petkov <bp@xxxxxxx> >> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx> >> --- >> Documentation/kdump/vmcoreinfo.txt | 500 +++++++++++++++++++++++++++++ >> 1 file changed, 500 insertions(+) >> create mode 100644 Documentation/kdump/vmcoreinfo.txt > > Ok, below is what I'm going to commit if no one complains. I hope you'd > find some time to work on adding the checkpatch check for patches which > add vmcoreinfo members but do not document them I noticed that the checkpatch was coded in Perl. But i am not familiar with the Perl program language, that would be beyond my ability to do this, i have to learn the Perl program language step by step. :-) > and also remove those vmcoreinfo members which are unused. > Do you mean this one 'KERNEL_IMAGE_SIZE'? Currently unused by Makedumpfile, but used to compute the module virtual address by Crash. I have corrected this issue in VMCOREINFO doc. Thanks. Lianbo > Which should be easy because we don't have to be backwards-compatible > with makedumpfile as this is not an ABI. > > Thx. > > --- > From: Lianbo Jiang <lijiang@xxxxxxxxxx> > Date: Thu, 10 Jan 2019 20:19:43 +0800 > Subject: [PATCH] kdump: Document kernel data exported in the vmcoreinfo note > > Document data exported in vmcoreinfo and briefly describe its use by > userspace tools.a > > [ bp: heavily massage and redact the text. ] > > Suggested-by: Borislav Petkov <bp@xxxxxxx> > Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx> > Signed-off-by: Borislav Petkov <bp@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Baoquan He <bhe@xxxxxxxxxx> > Cc: Dave Young <dyoung@xxxxxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> > Cc: anderson@xxxxxxxxxx > Cc: k-hagio@xxxxxxxxxxxxx > Cc: kexec@xxxxxxxxxxxxxxxxxxx > Cc: linux-doc@xxxxxxxxxxxxxxx > Cc: mingo@xxxxxxxxxx > Cc: x86-ml <x86@xxxxxxxxxx> > Link: https://lkml.kernel.org/r/20190110121944.6050-2-lijiang@xxxxxxxxxx > --- > Documentation/kdump/vmcoreinfo.txt | 494 +++++++++++++++++++++++++++++ > 1 file changed, 494 insertions(+) > create mode 100644 Documentation/kdump/vmcoreinfo.txt > > diff --git a/Documentation/kdump/vmcoreinfo.txt b/Documentation/kdump/vmcoreinfo.txt > new file mode 100644 > index 000000000000..2dc3797940a3 > --- /dev/null > +++ b/Documentation/kdump/vmcoreinfo.txt > @@ -0,0 +1,494 @@ > +================================================================ > + VMCOREINFO > +================================================================ > + > +=========== > +What is it? > +=========== > + > +VMCOREINFO is a special ELF note section. It contains various > +information from the kernel like structure size, page size, symbol > +values, field offsets, etc. These data are packed into an ELF note > +section and used by user-space tools like crash and makedumpfile to > +analyze a kernel's memory layout. > + > +================ > +Common variables > +================ > + > +init_uts_ns.name.release > +------------------------ > + > +The version of the Linux kernel. Used to find the corresponding source > +code from which the kernel has been built. > + > +PAGE_SIZE > +--------- > + > +The size of a page. It is the smallest unit of data used by the memory > +management facilities. It is usually 4096 bytes of size and a page is > +aligned on 4096 bytes. Used for computing page addresses. > + > +init_uts_ns > +----------- > + > +The UTS namespace which is used to isolate two specific elements of the > +system that relate to the uname(2) system call. It is named after the > +data structure used to store information returned by the uname(2) system > +call. > + > +User-space tools can get the kernel name, host name, kernel release > +number, kernel version, architecture name and OS type from it. > + > +node_online_map > +--------------- > + > +An array node_states[N_ONLINE] which represents the set of online nodes > +in a system, one bit position per node number. Used to keep track of > +which nodes are in the system and online. > + > +swapper_pg_dir > +------------- > + > +The global page directory pointer of the kernel. Used to translate > +virtual to physical addresses. > + > +_stext > +------ > + > +Defines the beginning of the text section. In general, _stext indicates > +the kernel start address. Used to convert a virtual address from the > +direct kernel map to a physical address. > + > +vmap_area_list > +-------------- > + > +Stores the virtual area list. makedumpfile gets the vmalloc start value > +from this variable and its value is necessary for vmalloc translation. > + > +mem_map > +------- > + > +Physical addresses are translated to struct pages by treating them as > +an index into the mem_map array. Right-shifting a physical address > +PAGE_SHIFT bits converts it into a page frame number which is an index > +into that mem_map array. > + > +Used to map an address to the corresponding struct page. > + > +contig_page_data > +---------------- > + > +Makedumpfile gets the pglist_data structure from this symbol, which is > +used to describe the memory layout. > + > +User-space tools use this to exclude free pages when dumping memory. > + > +mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map) > +-------------------------------------------------------------------------- > + > +The address of the mem_section array, its length, structure size, and > +the section_mem_map offset. > + > +It exists in the sparse memory mapping model, and it is also somewhat > +similar to the mem_map variable, both of them are used to translate an > +address. > + > +page > +---- > + > +The size of a page structure. struct page is an important data structure > +and it is widely used to compute contiguous memory. > + > +pglist_data > +----------- > + > +The size of a pglist_data structure. This value is used to check if the > +pglist_data structure is valid. It is also used for checking the memory > +type. > + > +zone > +---- > + > +The size of a zone structure. This value is used to check if the zone > +structure has been found. It is also used for excluding free pages. > + > +free_area > +--------- > + > +The size of a free_area structure. It indicates whether the free_area > +structure is valid or not. Useful when excluding free pages. > + > +list_head > +--------- > + > +The size of a list_head structure. Used when iterating lists in a > +post-mortem analysis session. > + > +nodemask_t > +---------- > + > +The size of a nodemask_t type. Used to compute the number of online > +nodes. > + > +(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor| > + compound_order|compound_head) > +------------------------------------------------------------------- > + > +User-space tools compute their values based on the offset of these > +variables. The variables are used when excluding unnecessary pages. > + > +(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_ > + spanned_pages|node_id) > +------------------------------------------------------------------- > + > +On NUMA machines, each NUMA node has a pg_data_t to describe its memory > +layout. On UMA machines there is a single pglist_data which describes the > +whole memory. > + > +These values are used to check the memory type and to compute the > +virtual address for memory map. > + > +(zone, free_area|vm_stat|spanned_pages) > +--------------------------------------- > + > +Each node is divided into a number of blocks called zones which > +represent ranges within memory. A zone is described by a structure zone. > + > +User-space tools compute required values based on the offset of these > +variables. > + > +(free_area, free_list) > +---------------------- > + > +Offset of the free_list's member. This value is used to compute the number > +of free pages. > + > +Each zone has a free_area structure array called free_area[MAX_ORDER]. > +The free_list represents a linked list of free page blocks. > + > +(list_head, next|prev) > +---------------------- > + > +Offsets of the list_head's members. list_head is used to define a > +circular linked list. User-space tools need these in order to traverse > +lists. > + > +(vmap_area, va_start|list) > +-------------------------- > + > +Offsets of the vmap_area's members. They carry vmalloc-specific > +information. Makedumpfile gets the start address of the vmalloc region > +from this. > + > +(zone.free_area, MAX_ORDER) > +--------------------------- > + > +Free areas descriptor. User-space tools use this value to iterate the > +free_area ranges. MAX_ORDER is used by the zone buddy allocator. > + > +log_first_idx > +------------- > + > +Index of the first record stored in the buffer log_buf. Used by > +user-space tools to read the strings in the log_buf. > + > +log_buf > +------- > + > +Console output is written to the ring buffer log_buf at index > +log_first_idx. Used to get the kernel log. > + > +log_buf_len > +----------- > + > +log_buf's length. > + > +clear_idx > +--------- > + > +The index that the next printk() record to read after the last clear > +command. It indicates the first record after the last SYSLOG_ACTION > +_CLEAR, like issued by 'dmesg -c'. Used by user-space tools to dump > +the dmesg log. > + > +log_next_idx > +------------ > + > +The index of the next record to store in the buffer log_buf. Used to > +compute the index of the current buffer position. > + > +printk_log > +---------- > + > +The size of a structure printk_log. Used to compute the size of > +messages, and extract dmesg log. It encapsulates header information for > +log_buf, such as timestamp, syslog level, etc. > + > +(printk_log, ts_nsec|len|text_len|dict_len) > +------------------------------------------- > + > +It represents field offsets in struct printk_log. User space tools > +parse it and check whether the values of printk_log's members have been > +changed. > + > +(free_area.free_list, MIGRATE_TYPES) > +------------------------------------ > + > +The number of migrate types for pages. The free_list is described by the > +array. Used by tools to compute the number of free pages. > + > +NR_FREE_PAGES > +------------- > + > +On linux-2.6.21 or later, the number of free pages is in > +vm_stat[NR_FREE_PAGES]. Used to get the number of free pages. > + > +PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision > +|PG_head_mask|PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy) > +|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline) > +----------------------------------------------------------------- > + > +Page attributes. These flags are used to filter various unnecessary for > +dumping pages. > + > +HUGETLB_PAGE_DTOR > +----------------- > + > +The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile > +excludes these pages. > + > +====== > +x86_64 > +====== > + > +phys_base > +--------- > + > +Used to convert the virtual address of an exported kernel symbol to its > +corresponding physical address. > + > +init_top_pgt > +------------ > + > +Used to walk through the whole page table and convert virtual addresses > +to physical addresses. The init_top_pgt is somewhat similar to > +swapper_pg_dir, but it is only used in x86_64. > + > +pgtable_l5_enabled > +------------------ > + > +User-space tools need to know whether the crash kernel was in 5-level > +paging mode. > + > +node_data > +--------- > + > +This is a struct pglist_data array and stores all NUMA nodes > +information. Makedumpfile gets the pglist_data structure from it. > + > +(node_data, MAX_NUMNODES) > +------------------------- > + > +The maximum number of nodes in system. > + > +KERNELOFFSET > +------------ > + > +The kernel randomization offset. Used to compute the page offset. If > +KASLR is disabled, this value is zero. > + > +KERNEL_IMAGE_SIZE > +----------------- > + > +Currently unused by Makedumpfile. Used to compute the module virtual > +address by Crash. > + > +sme_mask > +-------- > + > +AMD-specific with SME support: it indicates the secure memory encryption > +mask. Makedumpfile tools need to know whether the crash kernel was > +encrypted. If SME is enabled in the first kernel, the crash kernel's > +page table entries (pgd/pud/pmd/pte) contain the memory encryption > +mask. This is used to remove the SME mask and obtain the true physical > +address. > + > +Currently, sme_mask stores the value of the C-bit position. If needed, > +additional SME-relevant info can be placed in that variable. > + > +For example: > +[ misc ][ enc bit ][ other misc SME info ] > +0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000 > +63 59 55 51 47 43 39 35 31 27 ... 3 > + > +====== > +x86_32 > +====== > + > +X86_PAE > +------- > + > +Denotes whether physical address extensions are enabled. It has the cost > +of a higher page table lookup overhead, and also consumes more page > +table space per process. Used to check whether PAE was enabled in the > +crash kernel when converting virtual addresses to physical addresses. > + > +==== > +ia64 > +==== > + > +pgdat_list|(pgdat_list, MAX_NUMNODES) > +------------------------------------- > + > +pg_data_t array storing all NUMA nodes information. MAX_NUMNODES > +indicates the number of the nodes. > + > +node_memblk|(node_memblk, NR_NODE_MEMBLKS) > +------------------------------------------ > + > +List of node memory chunks. Filled when parsing the SRAT table to obtain > +information about memory nodes. NR_NODE_MEMBLKS indicates the number of > +node memory chunks. > + > +These values are used to compute the number of nodes the crashed kernel used. > + > +node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size) > +---------------------------------------------------------------- > + > +The size of a struct node_memblk_s and the offsets of the > +node_memblk_s's members. Used to compute the number of nodes. > + > +PGTABLE_3|PGTABLE_4 > +------------------- > + > +User-space tools need to know whether the crash kernel was in 3-level or > +4-level paging mode. Used to distinguish the page table. > + > +===== > +ARM64 > +===== > + > +VA_BITS > +------- > + > +The maximum number of bits for virtual addresses. Used to compute the > +virtual memory ranges. > + > +kimage_voffset > +-------------- > + > +The offset between the kernel virtual and physical mappings. Used to > +translate virtual to physical addresses. > + > +PHYS_OFFSET > +----------- > + > +Indicates the physical address of the start of memory. Similar to > +kimage_voffset, which is used to translate virtual to physical > +addresses. > + > +KERNELOFFSET > +------------ > + > +The kernel randomization offset. Used to compute the page offset. If > +KASLR is disabled, this value is zero. > + > +==== > +arm > +==== > + > +ARM_LPAE > +-------- > + > +It indicates whether the crash kernel supports large physical address > +extensions. Used to translate virtual to physical addresses. > + > +==== > +s390 > +==== > + > +lowcore_ptr > +---------- > + > +An array with a pointer to the lowcore of every CPU. Used to print the > +psw and all registers information. > + > +high_memory > +----------- > + > +Used to get the vmalloc_start address from the high_memory symbol. > + > +(lowcore_ptr, NR_CPUS) > +---------------------- > + > +The maximum number of CPUs. > + > +======= > +powerpc > +======= > + > + > +node_data|(node_data, MAX_NUMNODES) > +----------------------------------- > + > +See above. > + > +contig_page_data > +---------------- > + > +See above. > + > +vmemmap_list > +------------ > + > +The vmemmap_list maintains the entire vmemmap physical mapping. Used > +to get vmemmap list count and populated vmemmap regions info. If the > +vmemmap address translation information is stored in the crash kernel, > +it is used to translate vmemmap kernel virtual addresses. > + > +mmu_vmemmap_psize > +----------------- > + > +The size of a page. Used to translate virtual to physical addresses. > + > +mmu_psize_defs > +-------------- > + > +Page size definitions, i.e. 4k, 64k, or 16M. > + > +Used to make vtop translations. > + > +vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)| > +(vmemmap_backing, virt_addr) > +---------------------------------------------------------------- > + > +The vmemmap virtual address space management does not have a traditional > +page table to track which virtual struct pages are backed by a physical > +mapping. The virtual to physical mappings are tracked in a simple linked > +list format. > + > +User-space tools need to know the offset of list, phys and virt_addr > +when computing the count of vmemmap regions. > + > +mmu_psize_def|(mmu_psize_def, shift) > +------------------------------------ > + > +The size of a struct mmu_psize_def and the offset of mmu_psize_def's > +member. > + > +Used in vtop translations. > + > +== > +sh > +== > + > +node_data|(node_data, MAX_NUMNODES) > +----------------------------------- > + > +See above. > + > +X2TLB > +----- > + > +Indicates whether the crashed kernel enabled SH extended mode. > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec