67 lines
2.9 KiB
ArmAsm
67 lines
2.9 KiB
ArmAsm
// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
|
|
// SPDX-License-Identifier: BSD-3-Clause
|
|
|
|
#include "textflag.h"
|
|
|
|
// ABI-checking trampoline for LoongArch 64. Sets a sentinel value in the
|
|
// register the Go ABI fixes across calls before entering the JIT function
|
|
// and checks whether it survived on return.
|
|
//
|
|
// The return trampoline (leaveJITCheckedRaw) is a raw TEXT symbol with no
|
|
// Go function declaration, so the toolchain does NOT interpose an
|
|
// ABIInternal wrapper — the JIT function RETs directly into the check
|
|
// code, which sees the registers exactly as the function left them.
|
|
//
|
|
// Go ABI on loong64 guarantees:
|
|
// - R22 holds the goroutine pointer (g) and must survive across any
|
|
// call. Go keeps no hardware frame pointer on loong64. The assembler
|
|
// spells this register "g"; R22 is not accepted.
|
|
|
|
// Sentinel value chosen to be unlikely in normal execution.
|
|
#define SENTINEL_G 0x0BADF00DDEADBEEF
|
|
|
|
// GLOBL holding the raw address of the leave trampoline, read by Go.
|
|
GLOBL ·leaveCheckedPtr(SB), NOPTR, $8
|
|
DATA ·leaveCheckedPtr(SB)/8, $·leaveJITCheckedRaw(SB)
|
|
|
|
// func enterJITChecked(fn uintptr, stack uintptr)
|
|
// Sets a sentinel in g (R22), switches to the prepared stack and jumps to
|
|
// fn. The prepared stack's first word must be the address of
|
|
// leaveJITCheckedRaw (read from leaveCheckedPtr). Only R4 and R5 are used
|
|
// as scratch: caller-saved, and R22 is not among them.
|
|
TEXT ·enterJITChecked(SB), NOSPLIT, $0-16
|
|
MOVV fn+0(FP), R4 // target function address (A0)
|
|
MOVV R1, savedRA(SB) // save return address (RA)
|
|
MOVV R3, savedSP(SB) // save Go stack pointer (SP)
|
|
MOVV g, savedG(SB) // save g
|
|
MOVV $SENTINEL_G, g // sentinel in g
|
|
MOVV stack+8(FP), R5 // load prepared stack pointer (A1)
|
|
MOVV 0(R5), R1 // load leaveJITCheckedRaw into RA
|
|
ADDV $8, R5, R5 // advance past the return slot
|
|
MOVV R5, R3 // switch to prepared stack (SP)
|
|
JIRL R0, R4, 0 // jump to JIT function
|
|
|
|
// leaveJITCheckedRaw is the raw return trampoline. It has NO Go function
|
|
// declaration, so no ABIInternal wrapper is generated — the JIT function's
|
|
// RET lands here directly, seeing g exactly as the function left it. It
|
|
// checks the sentinel, records violations in abiResult, then restores the
|
|
// Go stack and returns.
|
|
TEXT ·leaveJITCheckedRaw(SB), NOSPLIT, $0-0
|
|
// Check g against the sentinel.
|
|
MOVV $SENTINEL_G, R5
|
|
BEQ g, R5, g_ok
|
|
MOVV ·abiResult(SB), R4
|
|
MOVV $2, R6
|
|
OR R6, R4, R4
|
|
MOVV R4, ·abiResult(SB)
|
|
|
|
g_ok:
|
|
MOVV savedSP(SB), R5 // restore Go stack pointer
|
|
MOVV R5, R3
|
|
MOVV savedRA(SB), R1 // restore return address
|
|
MOVV savedG(SB), g // restore g: Go code needs it the moment it
|
|
// resumes, violation or not
|
|
JIRL R0, R1, 0 // return to Go caller
|
|
|
|
GLOBL savedG(SB), NOPTR, $8
|