These docs are under active development and cover the v0.20 Kobicha security model.
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§8.1

Constants

All numeric constants used in the KMES interface. An independent implementer can derive all magic numbers from this page.

§8.1.1 Syscall numbers

Syscall Number Description
kmes_emit 1090 Emit a single event from userspace.
kmes_attach 1091 Attach as a consumer and obtain per-CPU ring buffer file descriptors.
kmes_emit_batch 1092 Emit multiple events from userspace as a single operation. Maximum 256 events per call.

§8.1.2 Origin class values

Value Origin
0 Userspace (syscall)
1 KMES
2 KACS
3 LCS

Values 4--255 are reserved for future kernel subsystems.

§8.1.3 Event header layout

Packed, no padding. All multi-byte integers little-endian.

Offset Size Type Field
0 4 u32 event_size
4 4 u32 header_size
8 8 u64 timestamp
16 8 u64 sequence
24 2 u16 cpu_id
26 1 u8 origin_class
27 2 u16 type_len
29 var [u8] type

Minimum header size: 29 + type_len bytes. Actual header_size MAY be larger (reserved space for future identity stamp fields). Payload begins at header_size from event start.

§8.1.4 Ring buffer metadata page layout

One metadata page (4096 bytes) per CPU. Cache-line-aligned fields.

§8.1.4.1 Cache line 0 -- static fields (bytes 0--63)

Offset Size Type Field
0 8 [u8; 8] magic
8 4 u32 version
12 2 u16 cpu_id
14 2 u16 reserved0
16 8 u64 capacity
24 8 u64 data_offset
32 8 u64 generation
40 24 -- reserved1

§8.1.4.2 Cache line 1 -- producer fields (bytes 64--127)

Offset Size Type Field
64 8 u64 write_pos
72 8 u64 tail_pos
80 48 -- reserved2

§8.1.4.3 Cache line 2 -- notification fields (bytes 128--191)

Offset Size Type Field
128 4 u32 futex_counter
132 1 u8 need_wake
133 59 -- reserved3

§8.1.5 Ring buffer magic 

0x4B 0x4D 0x45 0x53 0x52 0x49 0x4E 0x47
 K    M    E    S    R    I    N    G

Compared byte-by-byte, not as an integer. Endianness-independent.

§8.1.6 Ring buffer version

v0.20 uses ring buffer format version 1.

§8.1.7 Mapped region layout

Per-CPU mapping returned by mmap() on a kmes_attach file descriptor:

Offset Size Description
0 4096 Metadata page
4096 2 × capacity Double-mapped data region

Total mapping size: 4096 + (2 × capacity) bytes.

§8.1.8 Syscall error codes

§8.1.8.1 kmes_emit errors

Errno Condition
EPERM Caller does not hold SeAuditPrivilege.
EINVAL Event type length is zero, or payload is invalid msgpack, or payload nesting depth exceeds MaxNestingDepth.
EFAULT Event type or payload pointer is inaccessible.
ENOSPC Event exceeds MaxEventSize or 50% of per-CPU ring buffer capacity.
ENOMEM Kernel memory allocation for staging buffer failed.

§8.1.8.2 kmes_emit_batch errors

Errno Condition
EPERM Caller does not hold SeAuditPrivilege.
EINVAL Count is 0 or exceeds 256, or failing entry has zero-length event type, or failing entry's payload is invalid msgpack or exceeds MaxNestingDepth.
EFAULT Entry array, event type, or payload pointer is inaccessible.
ENOSPC Failing entry exceeds MaxEventSize or 50% of per-CPU ring buffer capacity.
ENOMEM Kernel memory allocation failed.

§8.1.8.3 kmes_attach errors

Errno Condition
EPERM Caller does not hold SeSecurityPrivilege.
ERANGE Provided buffer is too small. *count set to required number.
EFAULT fds or count pointer is inaccessible.
ENOMEM Kernel memory allocation failed.

§8.1.9 Configuration keys

Registry path: Machine\System\KMES\

Key Type Default Valid range
BufferCapacity REG_QWORD 4194304 (4 MB) 65536--268435456 (64 KB--256 MB), power of two
MaxEventSize REG_DWORD 65536 (64 KB) 1024--4194304 (1 KB--4 MB)
MaxNestingDepth REG_DWORD 32 4--256

§8.1.10 Privilege requirements

Operation Required privilege
Emit event from userspace (kmes_emit, kmes_emit_batch) SeAuditPrivilege
Attach as consumer (kmes_attach) SeSecurityPrivilege