With the introduction of the lockless printk ringbuffer, the VMCOREINFO relating to the kernel log buffer was changed. Update the documentation to match those changes. Fixes: ("printk: use the lockless ringbuffer") Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx> Reported-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> --- based on next-20200814 .../admin-guide/kdump/vmcoreinfo.rst | 131 ++++++++++++++---- 1 file changed, 102 insertions(+), 29 deletions(-) diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst index 2baad0bfb09d..eb116905c31c 100644 --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -189,50 +189,123 @@ from this. 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 +prb +--- + +A pointer to the printk ringbuffer (struct printk_ringbuffer). This +may be pointing to the static boot ringbuffer or the dynamically +allocated ringbuffer, depending on when the the core dump occurred. +Used by user-space tools to read the active kernel log buffer. + +printk_rb_static +---------------- + +A pointer to the static boot printk ringbuffer. If @prb has a +different value, this is useful for viewing the initial boot messages, +which may have been overwritten in the dynamically allocated +ringbuffer. + +clear_seq +--------- + +The sequence number of the printk() record 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 a subset of the dmesg log. + +printk_ringbuffer +----------------- + +The size of a printk_ringbuffer structure. This structure contains all +information required for accessing the various components of the +kernel log buffer. + +(printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail) +----------------------------------------------------------------- + +Offsets for the various components of the printk ringbuffer. Used by +user-space tools to view the kernel log buffer without requiring the +declaration of the structure. + +prb_desc_ring ------------- -Index of the first record stored in the buffer log_buf. Used by -user-space tools to read the strings in the log_buf. +The size of the prb_desc_ring structure. This structure contains +information about the set of record descriptors. -log_buf -------- +(prb_desc_ring, count_bits|descs|head_id|tail_id) +------------------------------------------------- + +Offsets for the fields describing the set of record descriptors. Used +by user-space tools to be able to traverse the descriptors without +requiring the declaration of the structure. + +prb_desc +-------- + +The size of the prb_desc structure. This structure contains +information about a single record descriptor. + +(prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos) +------------------------------------------------------ + +Offsets for the fields describing a record descriptors. Used by +user-space tools to be able to read descriptors without requiring +the declaration of the structure. + +prb_data_blk_lpos +----------------- + +The size of the prb_data_blk_lpos structure. This structure contains +information about where the text or dictionary data (data block) is +located within the respective data ring. + +(prb_data_blk_lpos, begin|next) +------------------------------- -Console output is written to the ring buffer log_buf at index -log_first_idx. Used to get the kernel log. +Offsets for the fields describing the location of a data block. Used +by user-space tools to be able to locate data blocks without +requiring the declaration of the structure. -log_buf_len +printk_info ----------- -log_buf's length. +The size of the printk_info structure. This structure contains all +the meta-data for a record. -clear_idx ---------- +(printk_info, seq|ts_nsec|text_len|dict_len|caller_id) +------------------------------------------------------ -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. +Offsets for the fields providing the meta-data for a record. Used by +user-space tools to be able to read the information without requiring +the declaration of the structure. -log_next_idx ------------- +prb_data_ring +------------- -The index of the next record to store in the buffer log_buf. Used to -compute the index of the current buffer position. +The size of the prb_data_ring structure. This structure contains +information about a set of data blocks. -printk_log ----------- +(prb_data_ring, size_bits|data|head_lpos|tail_lpos) +--------------------------------------------------- -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. +Offsets for the fields describing a set of data blocks. Used by +user-space tools to be able to access the data blocks without +requiring the declaration of the structure. -(printk_log, ts_nsec|len|text_len|dict_len) -------------------------------------------- +atomic_long_t +------------- + +The size of the atomic_long_t structure. Used by user-space tools to +be able to copy the full structure, regardless of its +architecture-specific implementation. + +(atomic_long_t, counter) +------------------------ -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. +Offset for the long value of an atomic_long_t variable. Used by +user-space tools to access the long value without requiring the +architecture-specific declaration. (free_area.free_list, MIGRATE_TYPES) ------------------------------------ -- 2.20.1 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec