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 An array node_states[N_ONLINE] which represents the set of online nodes
46 in a system, one bit position per node number. Used to keep track of
47 which nodes are in the system and online.
52 The global page directory pointer of the kernel. Used to translate
53 virtual to physical addresses.
58 Defines the beginning of the text section. In general, _stext indicates
59 the kernel start address. Used to convert a virtual address from the
60 direct kernel map to a physical address.
65 Stores the virtual area list. makedumpfile gets the vmalloc start value
66 from this variable and its value is necessary for vmalloc translation.
71 Physical addresses are translated to struct pages by treating them as
72 an index into the mem_map array. Right-shifting a physical address
73 PAGE_SHIFT bits converts it into a page frame number which is an index
74 into that mem_map array.
76 Used to map an address to the corresponding struct page.
81 Makedumpfile gets the pglist_data structure from this symbol, which is
82 used to describe the memory layout.
84 User-space tools use this to exclude free pages when dumping memory.
86 mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map)
87 --------------------------------------------------------------------------
89 The address of the mem_section array, its length, structure size, and
90 the section_mem_map offset.
92 It exists in the sparse memory mapping model, and it is also somewhat
93 similar to the mem_map variable, both of them are used to translate an
99 Defines the maximum supported physical address space memory.
104 The size of a page structure. struct page is an important data structure
105 and it is widely used to compute contiguous memory.
110 The size of a pglist_data structure. This value is used to check if the
111 pglist_data structure is valid. It is also used for checking the memory
117 The size of a zone structure. This value is used to check if the zone
118 structure has been found. It is also used for excluding free pages.
123 The size of a free_area structure. It indicates whether the free_area
124 structure is valid or not. Useful when excluding free pages.
129 The size of a list_head structure. Used when iterating lists in a
130 post-mortem analysis session.
135 The size of a nodemask_t type. Used to compute the number of online
138 (page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|compound_order|compound_head)
139 -------------------------------------------------------------------------------------------------
141 User-space tools compute their values based on the offset of these
142 variables. The variables are used when excluding unnecessary pages.
144 (pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
145 -----------------------------------------------------------------------------------------
147 On NUMA machines, each NUMA node has a pg_data_t to describe its memory
148 layout. On UMA machines there is a single pglist_data which describes the
151 These values are used to check the memory type and to compute the
152 virtual address for memory map.
154 (zone, free_area|vm_stat|spanned_pages)
155 ---------------------------------------
157 Each node is divided into a number of blocks called zones which
158 represent ranges within memory. A zone is described by a structure zone.
160 User-space tools compute required values based on the offset of these
163 (free_area, free_list)
164 ----------------------
166 Offset of the free_list's member. This value is used to compute the number
169 Each zone has a free_area structure array called free_area[MAX_ORDER].
170 The free_list represents a linked list of free page blocks.
172 (list_head, next|prev)
173 ----------------------
175 Offsets of the list_head's members. list_head is used to define a
176 circular linked list. User-space tools need these in order to traverse
179 (vmap_area, va_start|list)
180 --------------------------
182 Offsets of the vmap_area's members. They carry vmalloc-specific
183 information. Makedumpfile gets the start address of the vmalloc region
186 (zone.free_area, MAX_ORDER)
187 ---------------------------
189 Free areas descriptor. User-space tools use this value to iterate the
190 free_area ranges. MAX_ORDER is used by the zone buddy allocator.
195 A pointer to the printk ringbuffer (struct printk_ringbuffer). This
196 may be pointing to the static boot ringbuffer or the dynamically
197 allocated ringbuffer, depending on when the the core dump occurred.
198 Used by user-space tools to read the active kernel log buffer.
203 A pointer to the static boot printk ringbuffer. If @prb has a
204 different value, this is useful for viewing the initial boot messages,
205 which may have been overwritten in the dynamically allocated
211 The sequence number of the printk() record after the last clear
212 command. It indicates the first record after the last
213 SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space
214 tools to dump a subset of the dmesg log.
219 The size of a printk_ringbuffer structure. This structure contains all
220 information required for accessing the various components of the
223 (printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail)
224 -----------------------------------------------------------------
226 Offsets for the various components of the printk ringbuffer. Used by
227 user-space tools to view the kernel log buffer without requiring the
228 declaration of the structure.
233 The size of the prb_desc_ring structure. This structure contains
234 information about the set of record descriptors.
236 (prb_desc_ring, count_bits|descs|head_id|tail_id)
237 -------------------------------------------------
239 Offsets for the fields describing the set of record descriptors. Used
240 by user-space tools to be able to traverse the descriptors without
241 requiring the declaration of the structure.
246 The size of the prb_desc structure. This structure contains
247 information about a single record descriptor.
249 (prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos)
250 ------------------------------------------------------
252 Offsets for the fields describing a record descriptors. Used by
253 user-space tools to be able to read descriptors without requiring
254 the declaration of the structure.
259 The size of the prb_data_blk_lpos structure. This structure contains
260 information about where the text or dictionary data (data block) is
261 located within the respective data ring.
263 (prb_data_blk_lpos, begin|next)
264 -------------------------------
266 Offsets for the fields describing the location of a data block. Used
267 by user-space tools to be able to locate data blocks without
268 requiring the declaration of the structure.
273 The size of the printk_info structure. This structure contains all
274 the meta-data for a record.
276 (printk_info, seq|ts_nsec|text_len|dict_len|caller_id)
277 ------------------------------------------------------
279 Offsets for the fields providing the meta-data for a record. Used by
280 user-space tools to be able to read the information without requiring
281 the declaration of the structure.
286 The size of the prb_data_ring structure. This structure contains
287 information about a set of data blocks.
289 (prb_data_ring, size_bits|data|head_lpos|tail_lpos)
290 ---------------------------------------------------
292 Offsets for the fields describing a set of data blocks. Used by
293 user-space tools to be able to access the data blocks without
294 requiring the declaration of the structure.
299 The size of the atomic_long_t structure. Used by user-space tools to
300 be able to copy the full structure, regardless of its
301 architecture-specific implementation.
303 (atomic_long_t, counter)
304 ------------------------
306 Offset for the long value of an atomic_long_t variable. Used by
307 user-space tools to access the long value without requiring the
308 architecture-specific declaration.
310 (free_area.free_list, MIGRATE_TYPES)
311 ------------------------------------
313 The number of migrate types for pages. The free_list is described by the
314 array. Used by tools to compute the number of free pages.
319 On linux-2.6.21 or later, the number of free pages is in
320 vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
322 PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
323 ------------------------------------------------------------------------------
325 Page attributes. These flags are used to filter various unnecessary for
328 PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
329 -----------------------------------------------------------------------------
331 More page attributes. These flags are used to filter various unnecessary for
338 The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
339 excludes these pages.
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.
419 pgdat_list|(pgdat_list, MAX_NUMNODES)
420 -------------------------------------
422 pg_data_t array storing all NUMA nodes information. MAX_NUMNODES
423 indicates the number of the nodes.
425 node_memblk|(node_memblk, NR_NODE_MEMBLKS)
426 ------------------------------------------
428 List of node memory chunks. Filled when parsing the SRAT table to obtain
429 information about memory nodes. NR_NODE_MEMBLKS indicates the number of
432 These values are used to compute the number of nodes the crashed kernel used.
434 node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size)
435 ----------------------------------------------------------------
437 The size of a struct node_memblk_s and the offsets of the
438 node_memblk_s's members. Used to compute the number of nodes.
443 User-space tools need to know whether the crash kernel was in 3-level or
444 4-level paging mode. Used to distinguish the page table.
452 The maximum number of bits for virtual addresses. Used to compute the
453 virtual memory ranges.
458 The offset between the kernel virtual and physical mappings. Used to
459 translate virtual to physical addresses.
464 Indicates the physical address of the start of memory. Similar to
465 kimage_voffset, which is used to translate virtual to physical
471 The kernel randomization offset. Used to compute the page offset. If
472 KASLR is disabled, this value is zero.
477 The mask to extract the Pointer Authentication Code from a kernel virtual
483 Indicates the size offset of the memory region addressed by TTBR1_EL1.
484 The region size is 2^(64-T1SZ) bytes.
486 TTBR1_EL1 is the table base address register specified by ARMv8-A
487 architecture which is used to lookup the page-tables for the Virtual
488 addresses in the higher VA range (refer to ARMv8 ARM document for
497 It indicates whether the crash kernel supports large physical address
498 extensions. Used to translate virtual to physical addresses.
506 An array with a pointer to the lowcore of every CPU. Used to print the
507 psw and all registers information.
512 Used to get the vmalloc_start address from the high_memory symbol.
514 (lowcore_ptr, NR_CPUS)
515 ----------------------
517 The maximum number of CPUs.
523 node_data|(node_data, MAX_NUMNODES)
524 -----------------------------------
536 The vmemmap_list maintains the entire vmemmap physical mapping. Used
537 to get vmemmap list count and populated vmemmap regions info. If the
538 vmemmap address translation information is stored in the crash kernel,
539 it is used to translate vmemmap kernel virtual addresses.
544 The size of a page. Used to translate virtual to physical addresses.
549 Page size definitions, i.e. 4k, 64k, or 16M.
551 Used to make vtop translations.
553 vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
554 --------------------------------------------------------------------------------------------
556 The vmemmap virtual address space management does not have a traditional
557 page table to track which virtual struct pages are backed by a physical
558 mapping. The virtual to physical mappings are tracked in a simple linked
561 User-space tools need to know the offset of list, phys and virt_addr
562 when computing the count of vmemmap regions.
564 mmu_psize_def|(mmu_psize_def, shift)
565 ------------------------------------
567 The size of a struct mmu_psize_def and the offset of mmu_psize_def's
570 Used in vtop translations.
575 node_data|(node_data, MAX_NUMNODES)
576 -----------------------------------
583 Indicates whether the crashed kernel enabled SH extended mode.