mirror of https://github.com/python/cpython
221 lines
8.1 KiB
Python
221 lines
8.1 KiB
Python
"""Core data structures for compiled code templates."""
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import dataclasses
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import enum
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import sys
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import _schema
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@enum.unique
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class HoleValue(enum.Enum):
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"""
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Different "base" values that can be patched into holes (usually combined with the
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address of a symbol and/or an addend).
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"""
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# The base address of the machine code for the current uop (exposed as _JIT_ENTRY):
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CODE = enum.auto()
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# The base address of the machine code for the next uop (exposed as _JIT_CONTINUE):
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CONTINUE = enum.auto()
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# The base address of the read-only data for this uop:
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DATA = enum.auto()
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# The address of the current executor (exposed as _JIT_EXECUTOR):
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EXECUTOR = enum.auto()
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# The base address of the "global" offset table located in the read-only data.
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# Shouldn't be present in the final stencils, since these are all replaced with
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# equivalent DATA values:
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GOT = enum.auto()
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# The current uop's oparg (exposed as _JIT_OPARG):
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OPARG = enum.auto()
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# The current uop's operand (exposed as _JIT_OPERAND):
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OPERAND = enum.auto()
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# The current uop's target (exposed as _JIT_TARGET):
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TARGET = enum.auto()
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# The base address of the machine code for the first uop (exposed as _JIT_TOP):
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TOP = enum.auto()
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# A hardcoded value of zero (used for symbol lookups):
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ZERO = enum.auto()
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@dataclasses.dataclass
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class Hole:
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"""
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A "hole" in the stencil to be patched with a computed runtime value.
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Analogous to relocation records in an object file.
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"""
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offset: int
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kind: _schema.HoleKind
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# Patch with this base value:
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value: HoleValue
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# ...plus the address of this symbol:
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symbol: str | None
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# ...plus this addend:
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addend: int
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# Convenience method:
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replace = dataclasses.replace
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def as_c(self) -> str:
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"""Dump this hole as an initialization of a C Hole struct."""
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parts = [
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f"{self.offset:#x}",
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f"HoleKind_{self.kind}",
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f"HoleValue_{self.value.name}",
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f"&{self.symbol}" if self.symbol else "NULL",
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_format_addend(self.addend),
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]
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return f"{{{', '.join(parts)}}}"
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@dataclasses.dataclass
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class Stencil:
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"""
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A contiguous block of machine code or data to be copied-and-patched.
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Analogous to a section or segment in an object file.
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"""
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body: bytearray = dataclasses.field(default_factory=bytearray, init=False)
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holes: list[Hole] = dataclasses.field(default_factory=list, init=False)
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disassembly: list[str] = dataclasses.field(default_factory=list, init=False)
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def pad(self, alignment: int) -> None:
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"""Pad the stencil to the given alignment."""
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offset = len(self.body)
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padding = -offset % alignment
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self.disassembly.append(f"{offset:x}: {' '.join(['00'] * padding)}")
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self.body.extend([0] * padding)
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def emit_aarch64_trampoline(self, hole: Hole) -> None:
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"""Even with the large code model, AArch64 Linux insists on 28-bit jumps."""
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base = len(self.body)
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where = slice(hole.offset, hole.offset + 4)
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instruction = int.from_bytes(self.body[where], sys.byteorder)
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instruction &= 0xFC000000
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instruction |= ((base - hole.offset) >> 2) & 0x03FFFFFF
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self.body[where] = instruction.to_bytes(4, sys.byteorder)
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self.disassembly += [
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f"{base + 4 * 0: x}: d2800008 mov x8, #0x0",
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f"{base + 4 * 0:016x}: R_AARCH64_MOVW_UABS_G0_NC {hole.symbol}",
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f"{base + 4 * 1:x}: f2a00008 movk x8, #0x0, lsl #16",
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f"{base + 4 * 1:016x}: R_AARCH64_MOVW_UABS_G1_NC {hole.symbol}",
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f"{base + 4 * 2:x}: f2c00008 movk x8, #0x0, lsl #32",
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f"{base + 4 * 2:016x}: R_AARCH64_MOVW_UABS_G2_NC {hole.symbol}",
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f"{base + 4 * 3:x}: f2e00008 movk x8, #0x0, lsl #48",
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f"{base + 4 * 3:016x}: R_AARCH64_MOVW_UABS_G3 {hole.symbol}",
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f"{base + 4 * 4:x}: d61f0100 br x8",
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]
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for code in [
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0xD2800008.to_bytes(4, sys.byteorder),
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0xF2A00008.to_bytes(4, sys.byteorder),
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0xF2C00008.to_bytes(4, sys.byteorder),
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0xF2E00008.to_bytes(4, sys.byteorder),
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0xD61F0100.to_bytes(4, sys.byteorder),
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]:
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self.body.extend(code)
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for i, kind in enumerate(
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[
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"R_AARCH64_MOVW_UABS_G0_NC",
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"R_AARCH64_MOVW_UABS_G1_NC",
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"R_AARCH64_MOVW_UABS_G2_NC",
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"R_AARCH64_MOVW_UABS_G3",
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]
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):
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self.holes.append(hole.replace(offset=base + 4 * i, kind=kind))
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@dataclasses.dataclass
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class StencilGroup:
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"""
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Code and data corresponding to a given micro-opcode.
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Analogous to an entire object file.
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"""
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code: Stencil = dataclasses.field(default_factory=Stencil, init=False)
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data: Stencil = dataclasses.field(default_factory=Stencil, init=False)
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symbols: dict[int | str, tuple[HoleValue, int]] = dataclasses.field(
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default_factory=dict, init=False
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)
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_got: dict[str, int] = dataclasses.field(default_factory=dict, init=False)
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def process_relocations(self, *, alignment: int = 1) -> None:
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"""Fix up all GOT and internal relocations for this stencil group."""
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self.code.pad(alignment)
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self.data.pad(8)
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for stencil in [self.code, self.data]:
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holes = []
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for hole in stencil.holes:
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if hole.value is HoleValue.GOT:
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assert hole.symbol is not None
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hole.value = HoleValue.DATA
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hole.addend += self._global_offset_table_lookup(hole.symbol)
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hole.symbol = None
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elif hole.symbol in self.symbols:
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hole.value, addend = self.symbols[hole.symbol]
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hole.addend += addend
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hole.symbol = None
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elif (
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hole.kind in {"R_AARCH64_CALL26", "R_AARCH64_JUMP26"}
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and hole.value is HoleValue.ZERO
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):
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self.code.emit_aarch64_trampoline(hole)
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continue
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holes.append(hole)
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stencil.holes[:] = holes
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self.code.pad(alignment)
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self._emit_global_offset_table()
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self.code.holes.sort(key=lambda hole: hole.offset)
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self.data.holes.sort(key=lambda hole: hole.offset)
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def _global_offset_table_lookup(self, symbol: str) -> int:
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return len(self.data.body) + self._got.setdefault(symbol, 8 * len(self._got))
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def _emit_global_offset_table(self) -> None:
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got = len(self.data.body)
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for s, offset in self._got.items():
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if s in self.symbols:
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value, addend = self.symbols[s]
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symbol = None
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else:
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value, symbol = symbol_to_value(s)
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addend = 0
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self.data.holes.append(
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Hole(got + offset, "R_X86_64_64", value, symbol, addend)
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)
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value_part = value.name if value is not HoleValue.ZERO else ""
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if value_part and not symbol and not addend:
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addend_part = ""
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else:
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addend_part = f"&{symbol}" if symbol else ""
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addend_part += _format_addend(addend, signed=symbol is not None)
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if value_part:
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value_part += "+"
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self.data.disassembly.append(
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f"{len(self.data.body):x}: {value_part}{addend_part}"
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)
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self.data.body.extend([0] * 8)
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def symbol_to_value(symbol: str) -> tuple[HoleValue, str | None]:
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"""
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Convert a symbol name to a HoleValue and a symbol name.
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Some symbols (starting with "_JIT_") are special and are converted to their
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own HoleValues.
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"""
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if symbol.startswith("_JIT_"):
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try:
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return HoleValue[symbol.removeprefix("_JIT_")], None
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except KeyError:
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pass
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return HoleValue.ZERO, symbol
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def _format_addend(addend: int, signed: bool = False) -> str:
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addend %= 1 << 64
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if addend & (1 << 63):
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addend -= 1 << 64
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return f"{addend:{'+#x' if signed else '#x'}}"
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