Runtime.NativeTelemetrySeal

1module Runtime.NativeTelemetrySeal
2
3import Compiler.MachineX86Native
4import Compiler.MachineX86NativeAssembly
5import Runtime.TelemetrySeal
6import Runtime.NativeWordDigest
7
8-- SEALING AN ALPHATEL RECORD AT RUN TIME (docs/observability PRD item 9).
9-- Runtime.NativeTelemetry encodes a record as "ALPHATEL", the body, then
10-- the SHA-256 of the body in 64 lowercase hex characters.  A record whose
11-- body carries a clock reading can only be sealed where the reading is
12-- taken, so this routine does, in the executable, what the encoder does at
13-- build time for the rest of the body:
14--
15--   rdi  the body followed by its SHA-256 padding (0x80, zeros, the bit
16--        length), whole 64-byte blocks, in writable memory
17--   rsi  the number of blocks
18--   rdx  the record: "ALPHATEL" already at +0; the body is copied to +8
19--        and the hex digest written after it
20--   rcx  the body's length in bytes (nonzero)
21--   r8   a struct timespec (seconds, nanoseconds): its nanoseconds since
22--        the clock's epoch are written into the body at `sealMonotonicAt`
23--        first, so the digest covers them
24--   r9   a work area of `digestWorkBytes` bytes
25--
26-- It keeps the System V callee-saved registers it uses in the work area
27-- (the instruction set has no push) and returns.  Every 32-bit quantity is
28-- kept zero-extended in a 64-bit register and truncated by its 32-bit
29-- store; a rotation is a shift of the doubled word.  The digest is checked
30-- against the build-time encoder's by reading a record the executable
31-- wrote (scripts/ci/observability.sh: `alpha observe import alphatel`
32-- verifies every record's digest).
33def sealAssembly =
34  (telemetrySealAssemblyFor
35    (family X86NativeAssembly)
36    (family X86NativeRegister64)
37    digestX86Backend)
38
39def nativeTelemetrySealRoutine : Bytes =
40  (compiler-native-encode (family X86NativeAssembly) sealAssembly)