github.com/goshafaq/sonic@v0.0.0-20231026082336-871835fb94c6/loader/funcdata_latest.go

// go:build go1.18 && !go1.22
//go:build go1.18 && !go1.22
// +build go1.18,!go1.22

/*
 * Copyright 2021 ByteDance Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package loader

import (
	"os"
	"sort"
	"unsafe"

	"github.com/goshafaq/sonic/internal/rt"
)

type funcTab struct {
	entry   uint32
	funcoff uint32
}

type pcHeader struct {
	magic          uint32  // 0xFFFFFFF0
	pad1, pad2     uint8   // 0,0
	minLC          uint8   // min instruction size
	ptrSize        uint8   // size of a ptr in bytes
	nfunc          int     // number of functions in the module
	nfiles         uint    // number of entries in the file tab
	textStart      uintptr // base for function entry PC offsets in this module, equal to moduledata.text
	funcnameOffset uintptr // offset to the funcnametab variable from pcHeader
	cuOffset       uintptr // offset to the cutab variable from pcHeader
	filetabOffset  uintptr // offset to the filetab variable from pcHeader
	pctabOffset    uintptr // offset to the pctab variable from pcHeader
	pclnOffset     uintptr // offset to the pclntab variable from pcHeader
}

type bitVector struct {
	n        int32 // # of bits
	bytedata *uint8
}

type ptabEntry struct {
	name int32
	typ  int32
}

type textSection struct {
	vaddr    uintptr // prelinked section vaddr
	end      uintptr // vaddr + section length
	baseaddr uintptr // relocated section address
}

type modulehash struct {
	modulename   string
	linktimehash string
	runtimehash  *string
}

// findfuncbucket is an array of these structures.
// Each bucket represents 4096 bytes of the text segment.
// Each subbucket represents 256 bytes of the text segment.
// To find a function given a pc, locate the bucket and subbucket for
// that pc. Add together the idx and subbucket value to obtain a
// function index. Then scan the functab array starting at that
// index to find the target function.
// This table uses 20 bytes for every 4096 bytes of code, or ~0.5% overhead.
type findfuncbucket struct {
	idx         uint32
	_SUBBUCKETS [16]byte
}

type compilationUnit struct {
	fileNames []string
}

func makeFtab(funcs []_func, maxpc uint32) (ftab []funcTab, pclntabSize int64, startLocations []uint32) {
	// Allocate space for the pc->func table. This structure consists of a pc offset
	// and an offset to the func structure. After that, we have a single pc
	// value that marks the end of the last function in the binary.
	pclntabSize = int64(len(funcs)*2*int(_PtrSize) + int(_PtrSize))
	startLocations = make([]uint32, len(funcs))
	for i, f := range funcs {
		pclntabSize = rnd(pclntabSize, int64(_PtrSize))
		//writePCToFunc
		startLocations[i] = uint32(pclntabSize)
		pclntabSize += int64(uint8(_FUNC_SIZE) + f.nfuncdata*4 + uint8(f.npcdata)*4)
	}

	ftab = make([]funcTab, 0, len(funcs)+1)

	// write a map of pc->func info offsets
	for i, f := range funcs {
		ftab = append(ftab, funcTab{uint32(f.entryOff), uint32(startLocations[i])})
	}

	// Final entry of table is just end pc offset.
	ftab = append(ftab, funcTab{maxpc, 0})
	return
}

// Pcln table format: [...]funcTab + [...]_Func
func makePclntable(size int64, startLocations []uint32, funcs []_func, maxpc uint32, pcdataOffs [][]uint32, funcdataOffs [][]uint32) (pclntab []byte) {
	// Allocate space for the pc->func table. This structure consists of a pc offset
	// and an offset to the func structure. After that, we have a single pc
	// value that marks the end of the last function in the binary.
	pclntab = make([]byte, size, size)

	// write a map of pc->func info offsets
	offs := 0
	for i, f := range funcs {
		byteOrder.PutUint32(pclntab[offs:offs+4], uint32(f.entryOff))
		byteOrder.PutUint32(pclntab[offs+4:offs+8], uint32(startLocations[i]))
		offs += 8
	}
	// Final entry of table is just end pc offset.
	byteOrder.PutUint32(pclntab[offs:offs+4], maxpc)

	// write func info table
	for i := range funcs {
		off := startLocations[i]

		// write _func structure to pclntab
		fb := rt.BytesFrom(unsafe.Pointer(&funcs[i]), int(_FUNC_SIZE), int(_FUNC_SIZE))
		copy(pclntab[off:off+uint32(_FUNC_SIZE)], fb)
		off += uint32(_FUNC_SIZE)

		// NOTICE: _func.pcdata always starts from PcUnsafePoint, which is index 3
		for j := 3; j < len(pcdataOffs[i]); j++ {
			byteOrder.PutUint32(pclntab[off:off+4], uint32(pcdataOffs[i][j]))
			off += 4
		}

		// funcdata refs as offsets from gofunc
		for _, funcdata := range funcdataOffs[i] {
			byteOrder.PutUint32(pclntab[off:off+4], uint32(funcdata))
			off += 4
		}

	}

	return
}

// findfunc table used to map pc to belonging func,
// returns the index in the func table.
//
// All text section are divided into buckets sized _BUCKETSIZE(4K):
//
//	every bucket is divided into _SUBBUCKETS sized _SUB_BUCKETSIZE(64),
//	and it has a base idx to plus the offset stored in jth subbucket.
//
// see findfunc() in runtime/symtab.go
func writeFindfunctab(out *[]byte, ftab []funcTab) (start int) {
	start = len(*out)

	max := ftab[len(ftab)-1].entry
	min := ftab[0].entry
	nbuckets := (max - min + _BUCKETSIZE - 1) / _BUCKETSIZE
	n := (max - min + _SUB_BUCKETSIZE - 1) / _SUB_BUCKETSIZE

	tab := make([]findfuncbucket, 0, nbuckets)
	var s, e = 0, 0
	for i := 0; i < int(nbuckets); i++ {
		// store the start s-th func of the bucket
		var fb = findfuncbucket{idx: uint32(s)}

		// find the last e-th func of the bucket
		var pc = min + uint32((i+1)*_BUCKETSIZE)
		for ; e < len(ftab)-1 && ftab[e+1].entry <= pc; e++ {
		}

		for j := 0; j < _SUBBUCKETS && (i*_SUBBUCKETS+j) < int(n); j++ {
			// store the start func of the subbucket
			fb._SUBBUCKETS[j] = byte(uint32(s) - fb.idx)

			// find the s-th end func of the subbucket
			pc = min + uint32(i*_BUCKETSIZE) + uint32((j+1)*_SUB_BUCKETSIZE)
			for ; s < len(ftab)-1 && ftab[s+1].entry <= pc; s++ {
			}
		}

		s = e
		tab = append(tab, fb)
	}

	// write findfuncbucket
	if len(tab) > 0 {
		size := int(unsafe.Sizeof(findfuncbucket{})) * len(tab)
		*out = append(*out, rt.BytesFrom(unsafe.Pointer(&tab[0]), size, size)...)
	}
	return
}

func makeModuledata(name string, filenames []string, funcsp *[]Func, text []byte) (mod *moduledata) {
	mod = new(moduledata)
	mod.modulename = name

	// sort funcs by entry
	funcs := *funcsp
	sort.Slice(funcs, func(i, j int) bool {
		return funcs[i].EntryOff < funcs[j].EntryOff
	})
	*funcsp = funcs

	// make filename table
	cu := make([]string, 0, len(filenames))
	cu = append(cu, filenames...)
	cutab, filetab, cuOffs := makeFilenametab([]compilationUnit{{cu}})
	mod.cutab = cutab
	mod.filetab = filetab

	// make funcname table
	funcnametab, nameOffs := makeFuncnameTab(funcs)
	mod.funcnametab = funcnametab

	// mmap() text and funcdata segements
	p := os.Getpagesize()
	size := int(rnd(int64(len(text)), int64(p)))
	addr := mmap(size)
	// copy the machine code
	s := rt.BytesFrom(unsafe.Pointer(addr), len(text), size)
	copy(s, text)
	// make it executable
	mprotect(addr, size)

	// assign addresses
	mod.text = addr
	mod.etext = addr + uintptr(size)
	mod.minpc = addr
	mod.maxpc = addr + uintptr(len(text))

	// make pcdata table
	// NOTICE: _func only use offset to index pcdata, thus no need mmap() pcdata
	cuOff := cuOffs[0]
	pctab, pcdataOffs, _funcs := makePctab(funcs, cuOff, nameOffs)
	mod.pctab = pctab

	// write func data
	// NOTICE: _func use mod.gofunc+offset to directly point funcdata, thus need cache funcdata
	// TODO: estimate accurate capacity
	cache := make([]byte, 0, len(funcs)*int(_PtrSize))
	fstart, funcdataOffs := writeFuncdata(&cache, funcs)

	// make pc->func (binary search) func table
	ftab, pclntSize, startLocations := makeFtab(_funcs, uint32(len(text)))
	mod.ftab = ftab

	// write pc->func (modmap) findfunc table
	ffstart := writeFindfunctab(&cache, ftab)

	// cache funcdata and findfuncbucket
	moduleCache.Lock()
	moduleCache.m[mod] = cache
	moduleCache.Unlock()
	mod.gofunc = uintptr(unsafe.Pointer(&cache[fstart]))
	mod.findfunctab = uintptr(unsafe.Pointer(&cache[ffstart]))

	// make pclnt table
	pclntab := makePclntable(pclntSize, startLocations, _funcs, uint32(len(text)), pcdataOffs, funcdataOffs)
	mod.pclntable = pclntab

	// make pc header
	mod.pcHeader = &pcHeader{
		magic:          _Magic,
		minLC:          _MinLC,
		ptrSize:        _PtrSize,
		nfunc:          len(funcs),
		nfiles:         uint(len(cu)),
		textStart:      mod.text,
		funcnameOffset: getOffsetOf(moduledata{}, "funcnametab"),
		cuOffset:       getOffsetOf(moduledata{}, "cutab"),
		filetabOffset:  getOffsetOf(moduledata{}, "filetab"),
		pctabOffset:    getOffsetOf(moduledata{}, "pctab"),
		pclnOffset:     getOffsetOf(moduledata{}, "pclntable"),
	}

	// sepecial case: gcdata and gcbss must by non-empty
	mod.gcdata = uintptr(unsafe.Pointer(&emptyByte))
	mod.gcbss = uintptr(unsafe.Pointer(&emptyByte))

	return
}

// makePctab generates pcdelta->valuedelta tables for functions,
// and returns the table and the entry offset of every kind pcdata in the table.
func makePctab(funcs []Func, cuOffset uint32, nameOffset []int32) (pctab []byte, pcdataOffs [][]uint32, _funcs []_func) {
	_funcs = make([]_func, len(funcs))

	// Pctab offsets of 0 are considered invalid in the runtime. We respect
	// that by just padding a single byte at the beginning of runtime.pctab,
	// that way no real offsets can be zero.
	pctab = make([]byte, 1, 12*len(funcs)+1)
	pcdataOffs = make([][]uint32, len(funcs))

	for i, f := range funcs {
		_f := &_funcs[i]

		var writer = func(pc *Pcdata) {
			var ab []byte
			var err error
			if pc != nil {
				ab, err = pc.MarshalBinary()
				if err != nil {
					panic(err)
				}
				pcdataOffs[i] = append(pcdataOffs[i], uint32(len(pctab)))
			} else {
				ab = []byte{0}
				pcdataOffs[i] = append(pcdataOffs[i], _PCDATA_INVALID_OFFSET)
			}
			pctab = append(pctab, ab...)
		}

		if f.Pcsp != nil {
			_f.pcsp = uint32(len(pctab))
		}
		writer(f.Pcsp)
		if f.Pcfile != nil {
			_f.pcfile = uint32(len(pctab))
		}
		writer(f.Pcfile)
		if f.Pcline != nil {
			_f.pcln = uint32(len(pctab))
		}
		writer(f.Pcline)
		writer(f.PcUnsafePoint)
		writer(f.PcStackMapIndex)
		writer(f.PcInlTreeIndex)
		writer(f.PcArgLiveIndex)

		_f.entryOff = f.EntryOff
		_f.nameOff = nameOffset[i]
		_f.args = f.ArgsSize
		_f.deferreturn = f.DeferReturn
		// NOTICE: _func.pcdata is always as [PCDATA_UnsafePoint(0) : PCDATA_ArgLiveIndex(3)]
		_f.npcdata = uint32(_N_PCDATA)
		_f.cuOffset = cuOffset
		_f.funcID = f.ID
		_f.flag = f.Flag
		_f.nfuncdata = uint8(_N_FUNCDATA)
	}

	return
}

func registerFunction(name string, pc uintptr, textSize uintptr, fp int, args int, size uintptr, argptrs uintptr, localptrs uintptr) {
}