8 VMCOREINFO is a special ELF note section. It contains various
9 information from the kernel like structure size, page size, symbol
10 values, field offsets, etc. These data are packed into an ELF note
11 section and used by user-space tools like crash and makedumpfile to
12 analyze a kernel's memory layout.
17 init_uts_ns.name.release
18 ------------------------
20 The version of the Linux kernel. Used to find the corresponding source
21 code from which the kernel has been built. For example, crash uses it to
22 find the corresponding vmlinux in order to process vmcore.
27 The size of a page. It is the smallest unit of data used by the memory
28 management facilities. It is usually 4096 bytes of size and a page is
29 aligned on 4096 bytes. Used for computing page addresses.
34 The UTS namespace which is used to isolate two specific elements of the
35 system that relate to the uname(2) system call. It is named after the
36 data structure used to store information returned by the uname(2) system
39 User-space tools can get the kernel name, host name, kernel release
40 number, kernel version, architecture name and OS type from it.
45 Offset of the name's member. Crash Utility and Makedumpfile get
46 the start address of the init_uts_ns.name from this.
51 An array node_states[N_ONLINE] which represents the set of online nodes
52 in a system, one bit position per node number. Used to keep track of
53 which nodes are in the system and online.
58 The global page directory pointer of the kernel. Used to translate
59 virtual to physical addresses.
64 Defines the beginning of the text section. In general, _stext indicates
65 the kernel start address. Used to convert a virtual address from the
66 direct kernel map to a physical address.
71 Stores the virtual area list. makedumpfile gets the vmalloc start value
72 from this variable and its value is necessary for vmalloc translation.
77 Physical addresses are translated to struct pages by treating them as
78 an index into the mem_map array. Right-shifting a physical address
79 PAGE_SHIFT bits converts it into a page frame number which is an index
80 into that mem_map array.
82 Used to map an address to the corresponding struct page.
87 Makedumpfile gets the pglist_data structure from this symbol, which is
88 used to describe the memory layout.
90 User-space tools use this to exclude free pages when dumping memory.
92 mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map)
93 --------------------------------------------------------------------------
95 The address of the mem_section array, its length, structure size, and
96 the section_mem_map offset.
98 It exists in the sparse memory mapping model, and it is also somewhat
99 similar to the mem_map variable, both of them are used to translate an
105 Defines the maximum supported physical address space memory.
110 The size of a page structure. struct page is an important data structure
111 and it is widely used to compute contiguous memory.
116 The size of a pglist_data structure. This value is used to check if the
117 pglist_data structure is valid. It is also used for checking the memory
123 The size of a zone structure. This value is used to check if the zone
124 structure has been found. It is also used for excluding free pages.
129 The size of a free_area structure. It indicates whether the free_area
130 structure is valid or not. Useful when excluding free pages.
135 The size of a list_head structure. Used when iterating lists in a
136 post-mortem analysis session.
141 The size of a nodemask_t type. Used to compute the number of online
144 (page, flags|_refcount|mapping|lru|_mapcount|private|compound_order|compound_head)
145 ----------------------------------------------------------------------------------
147 User-space tools compute their values based on the offset of these
148 variables. The variables are used when excluding unnecessary pages.
150 (pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
151 -----------------------------------------------------------------------------------------
153 On NUMA machines, each NUMA node has a pg_data_t to describe its memory
154 layout. On UMA machines there is a single pglist_data which describes the
157 These values are used to check the memory type and to compute the
158 virtual address for memory map.
160 (zone, free_area|vm_stat|spanned_pages)
161 ---------------------------------------
163 Each node is divided into a number of blocks called zones which
164 represent ranges within memory. A zone is described by a structure zone.
166 User-space tools compute required values based on the offset of these
169 (free_area, free_list)
170 ----------------------
172 Offset of the free_list's member. This value is used to compute the number
175 Each zone has a free_area structure array called free_area[MAX_ORDER + 1].
176 The free_list represents a linked list of free page blocks.
178 (list_head, next|prev)
179 ----------------------
181 Offsets of the list_head's members. list_head is used to define a
182 circular linked list. User-space tools need these in order to traverse
185 (vmap_area, va_start|list)
186 --------------------------
188 Offsets of the vmap_area's members. They carry vmalloc-specific
189 information. Makedumpfile gets the start address of the vmalloc region
192 (zone.free_area, MAX_ORDER + 1)
193 -------------------------------
195 Free areas descriptor. User-space tools use this value to iterate the
196 free_area ranges. MAX_ORDER is used by the zone buddy allocator.
201 A pointer to the printk ringbuffer (struct printk_ringbuffer). This
202 may be pointing to the static boot ringbuffer or the dynamically
203 allocated ringbuffer, depending on when the core dump occurred.
204 Used by user-space tools to read the active kernel log buffer.
209 A pointer to the static boot printk ringbuffer. If @prb has a
210 different value, this is useful for viewing the initial boot messages,
211 which may have been overwritten in the dynamically allocated
217 The sequence number of the printk() record after the last clear
218 command. It indicates the first record after the last
219 SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space
220 tools to dump a subset of the dmesg log.
225 The size of a printk_ringbuffer structure. This structure contains all
226 information required for accessing the various components of the
229 (printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail)
230 -----------------------------------------------------------------
232 Offsets for the various components of the printk ringbuffer. Used by
233 user-space tools to view the kernel log buffer without requiring the
234 declaration of the structure.
239 The size of the prb_desc_ring structure. This structure contains
240 information about the set of record descriptors.
242 (prb_desc_ring, count_bits|descs|head_id|tail_id)
243 -------------------------------------------------
245 Offsets for the fields describing the set of record descriptors. Used
246 by user-space tools to be able to traverse the descriptors without
247 requiring the declaration of the structure.
252 The size of the prb_desc structure. This structure contains
253 information about a single record descriptor.
255 (prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos)
256 ------------------------------------------------------
258 Offsets for the fields describing a record descriptors. Used by
259 user-space tools to be able to read descriptors without requiring
260 the declaration of the structure.
265 The size of the prb_data_blk_lpos structure. This structure contains
266 information about where the text or dictionary data (data block) is
267 located within the respective data ring.
269 (prb_data_blk_lpos, begin|next)
270 -------------------------------
272 Offsets for the fields describing the location of a data block. Used
273 by user-space tools to be able to locate data blocks without
274 requiring the declaration of the structure.
279 The size of the printk_info structure. This structure contains all
280 the meta-data for a record.
282 (printk_info, seq|ts_nsec|text_len|dict_len|caller_id)
283 ------------------------------------------------------
285 Offsets for the fields providing the meta-data for a record. Used by
286 user-space tools to be able to read the information without requiring
287 the declaration of the structure.
292 The size of the prb_data_ring structure. This structure contains
293 information about a set of data blocks.
295 (prb_data_ring, size_bits|data|head_lpos|tail_lpos)
296 ---------------------------------------------------
298 Offsets for the fields describing a set of data blocks. Used by
299 user-space tools to be able to access the data blocks without
300 requiring the declaration of the structure.
305 The size of the atomic_long_t structure. Used by user-space tools to
306 be able to copy the full structure, regardless of its
307 architecture-specific implementation.
309 (atomic_long_t, counter)
310 ------------------------
312 Offset for the long value of an atomic_long_t variable. Used by
313 user-space tools to access the long value without requiring the
314 architecture-specific declaration.
316 (free_area.free_list, MIGRATE_TYPES)
317 ------------------------------------
319 The number of migrate types for pages. The free_list is described by the
320 array. Used by tools to compute the number of free pages.
325 On linux-2.6.21 or later, the number of free pages is in
326 vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
328 PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask|PG_hugetlb
329 -----------------------------------------------------------------------------------------
331 Page attributes. These flags are used to filter various unnecessary for
334 PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
335 -----------------------------------------------------------------------------
337 More page attributes. These flags are used to filter various unnecessary for
347 Used to convert the virtual address of an exported kernel symbol to its
348 corresponding physical address.
353 Used to walk through the whole page table and convert virtual addresses
354 to physical addresses. The init_top_pgt is somewhat similar to
355 swapper_pg_dir, but it is only used in x86_64.
360 User-space tools need to know whether the crash kernel was in 5-level
366 This is a struct pglist_data array and stores all NUMA nodes
367 information. Makedumpfile gets the pglist_data structure from it.
369 (node_data, MAX_NUMNODES)
370 -------------------------
372 The maximum number of nodes in system.
377 The kernel randomization offset. Used to compute the page offset. If
378 KASLR is disabled, this value is zero.
383 Currently unused by Makedumpfile. Used to compute the module virtual
389 AMD-specific with SME support: it indicates the secure memory encryption
390 mask. Makedumpfile tools need to know whether the crash kernel was
391 encrypted. If SME is enabled in the first kernel, the crash kernel's
392 page table entries (pgd/pud/pmd/pte) contain the memory encryption
393 mask. This is used to remove the SME mask and obtain the true physical
396 Currently, sme_mask stores the value of the C-bit position. If needed,
397 additional SME-relevant info can be placed in that variable.
401 [ misc ][ enc bit ][ other misc SME info ]
402 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
403 63 59 55 51 47 43 39 35 31 27 ... 3
411 Denotes whether physical address extensions are enabled. It has the cost
412 of a higher page table lookup overhead, and also consumes more page
413 table space per process. Used to check whether PAE was enabled in the
414 crash kernel when converting virtual addresses to physical addresses.
422 The maximum number of bits for virtual addresses. Used to compute the
423 virtual memory ranges.
428 The offset between the kernel virtual and physical mappings. Used to
429 translate virtual to physical addresses.
434 Indicates the physical address of the start of memory. Similar to
435 kimage_voffset, which is used to translate virtual to physical
441 The kernel randomization offset. Used to compute the page offset. If
442 KASLR is disabled, this value is zero.
447 The mask to extract the Pointer Authentication Code from a kernel virtual
453 Indicates the size offset of the memory region addressed by TTBR1_EL1.
454 The region size is 2^(64-T1SZ) bytes.
456 TTBR1_EL1 is the table base address register specified by ARMv8-A
457 architecture which is used to lookup the page-tables for the Virtual
458 addresses in the higher VA range (refer to ARMv8 ARM document for
461 MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END
462 -----------------------------------------------------------------------------
464 Used to get the correct ranges:
465 MODULES_VADDR ~ MODULES_END-1 : Kernel module space.
466 VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space.
467 VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array.
475 It indicates whether the crash kernel supports large physical address
476 extensions. Used to translate virtual to physical addresses.
484 An array with a pointer to the lowcore of every CPU. Used to print the
485 psw and all registers information.
490 Used to get the vmalloc_start address from the high_memory symbol.
492 (lowcore_ptr, NR_CPUS)
493 ----------------------
495 The maximum number of CPUs.
501 node_data|(node_data, MAX_NUMNODES)
502 -----------------------------------
514 The vmemmap_list maintains the entire vmemmap physical mapping. Used
515 to get vmemmap list count and populated vmemmap regions info. If the
516 vmemmap address translation information is stored in the crash kernel,
517 it is used to translate vmemmap kernel virtual addresses.
522 The size of a page. Used to translate virtual to physical addresses.
527 Page size definitions, i.e. 4k, 64k, or 16M.
529 Used to make vtop translations.
531 vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
532 --------------------------------------------------------------------------------------------
534 The vmemmap virtual address space management does not have a traditional
535 page table to track which virtual struct pages are backed by a physical
536 mapping. The virtual to physical mappings are tracked in a simple linked
539 User-space tools need to know the offset of list, phys and virt_addr
540 when computing the count of vmemmap regions.
542 mmu_psize_def|(mmu_psize_def, shift)
543 ------------------------------------
545 The size of a struct mmu_psize_def and the offset of mmu_psize_def's
548 Used in vtop translations.
553 node_data|(node_data, MAX_NUMNODES)
554 -----------------------------------
561 Indicates whether the crashed kernel enabled SH extended mode.
569 The maximum number of bits for virtual addresses. Used to compute the
570 virtual memory ranges.
575 Indicates the virtual kernel start address of the direct-mapped RAM region.
580 Indicates the start physical RAM address.
582 MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END|KERNEL_LINK_ADDR
583 ----------------------------------------------------------------------------------------------
585 Used to get the correct ranges:
587 * MODULES_VADDR ~ MODULES_END : Kernel module space.
588 * VMALLOC_START ~ VMALLOC_END : vmalloc() / ioremap() space.
589 * VMEMMAP_START ~ VMEMMAP_END : vmemmap space, used for struct page array.
590 * KERNEL_LINK_ADDR : start address of Kernel link and BPF
595 Indicates the offset between the kernel virtual and physical mappings.
596 Used to translate virtual to physical addresses.