| // Copyright 2014 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package runtime |
| |
| import "unsafe" |
| |
| // NOTE: Func does not expose the actual unexported fields, because we return *Func |
| // values to users, and we want to keep them from being able to overwrite the data |
| // with (say) *f = Func{}. |
| // All code operating on a *Func must call raw to get the *_func instead. |
| |
| // A Func represents a Go function in the running binary. |
| type Func struct { |
| opaque struct{} // unexported field to disallow conversions |
| } |
| |
| func (f *Func) raw() *_func { |
| return (*_func)(unsafe.Pointer(f)) |
| } |
| |
| // funcdata.h |
| const ( |
| _PCDATA_StackMapIndex = 0 |
| _FUNCDATA_ArgsPointerMaps = 0 |
| _FUNCDATA_LocalsPointerMaps = 1 |
| _FUNCDATA_DeadValueMaps = 2 |
| _ArgsSizeUnknown = -0x80000000 |
| ) |
| |
| // moduledata records information about the layout of the executable |
| // image. It is written by the linker. Any changes here must be |
| // matched changes to the code in cmd/internal/ld/symtab.go:symtab. |
| type moduledata struct { |
| pclntable []byte |
| ftab []functab |
| filetab []uint32 |
| findfunctab uintptr |
| minpc, maxpc uintptr |
| |
| text, etext uintptr |
| noptrdata, enoptrdata uintptr |
| data, edata uintptr |
| bss, ebss uintptr |
| noptrbss, enoptrbss uintptr |
| end, gcdata, gcbss uintptr |
| |
| typelinks []*_type |
| |
| gcdatamask, gcbssmask bitvector |
| |
| // write barrier shadow data |
| // 64-bit systems only, enabled by GODEBUG=wbshadow=1. |
| // See also the shadow_* fields on mheap in mheap.go. |
| shadow_data uintptr // data-addr + shadow_data = shadow data addr |
| data_start uintptr // start of shadowed data addresses |
| data_end uintptr // end of shadowed data addresses |
| |
| next *moduledata |
| } |
| |
| var firstmoduledata moduledata // linker symbol |
| var lastmoduledatap *moduledata // linker symbol |
| |
| type functab struct { |
| entry uintptr |
| funcoff uintptr |
| } |
| |
| const minfunc = 16 // minimum function size |
| const pcbucketsize = 256 * minfunc // size of bucket in the pc->func lookup table |
| |
| // findfunctab 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 |
| } |
| |
| func moduledataverify() { |
| for datap := &firstmoduledata; datap != nil; datap = datap.next { |
| moduledataverify1(datap) |
| } |
| } |
| |
| func moduledataverify1(datap *moduledata) { |
| // See golang.org/s/go12symtab for header: 0xfffffffb, |
| // two zero bytes, a byte giving the PC quantum, |
| // and a byte giving the pointer width in bytes. |
| pcln := *(**[8]byte)(unsafe.Pointer(&datap.pclntable)) |
| pcln32 := *(**[2]uint32)(unsafe.Pointer(&datap.pclntable)) |
| if pcln32[0] != 0xfffffffb || pcln[4] != 0 || pcln[5] != 0 || pcln[6] != _PCQuantum || pcln[7] != ptrSize { |
| println("runtime: function symbol table header:", hex(pcln32[0]), hex(pcln[4]), hex(pcln[5]), hex(pcln[6]), hex(pcln[7])) |
| throw("invalid function symbol table\n") |
| } |
| |
| // ftab is lookup table for function by program counter. |
| nftab := len(datap.ftab) - 1 |
| for i := 0; i < nftab; i++ { |
| // NOTE: ftab[nftab].entry is legal; it is the address beyond the final function. |
| if datap.ftab[i].entry > datap.ftab[i+1].entry { |
| f1 := (*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i].funcoff])) |
| f2 := (*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i+1].funcoff])) |
| f2name := "end" |
| if i+1 < nftab { |
| f2name = funcname(f2) |
| } |
| println("function symbol table not sorted by program counter:", hex(datap.ftab[i].entry), funcname(f1), ">", hex(datap.ftab[i+1].entry), f2name) |
| for j := 0; j <= i; j++ { |
| print("\t", hex(datap.ftab[j].entry), " ", funcname((*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[j].funcoff]))), "\n") |
| } |
| throw("invalid runtime symbol table") |
| } |
| } |
| |
| if datap.minpc != datap.ftab[0].entry || |
| datap.maxpc != datap.ftab[nftab].entry { |
| throw("minpc or maxpc invalid") |
| } |
| } |
| |
| // FuncForPC returns a *Func describing the function that contains the |
| // given program counter address, or else nil. |
| func FuncForPC(pc uintptr) *Func { |
| return (*Func)(unsafe.Pointer(findfunc(pc))) |
| } |
| |
| // Name returns the name of the function. |
| func (f *Func) Name() string { |
| return funcname(f.raw()) |
| } |
| |
| // Entry returns the entry address of the function. |
| func (f *Func) Entry() uintptr { |
| return f.raw().entry |
| } |
| |
| // FileLine returns the file name and line number of the |
| // source code corresponding to the program counter pc. |
| // The result will not be accurate if pc is not a program |
| // counter within f. |
| func (f *Func) FileLine(pc uintptr) (file string, line int) { |
| // Pass strict=false here, because anyone can call this function, |
| // and they might just be wrong about targetpc belonging to f. |
| file, line32 := funcline1(f.raw(), pc, false) |
| return file, int(line32) |
| } |
| |
| func findmoduledatap(pc uintptr) *moduledata { |
| for datap := &firstmoduledata; datap != nil; datap = datap.next { |
| if datap.minpc <= pc && pc <= datap.maxpc { |
| return datap |
| } |
| } |
| return nil |
| } |
| |
| func findfunc(pc uintptr) *_func { |
| datap := findmoduledatap(pc) |
| if datap == nil { |
| return nil |
| } |
| const nsub = uintptr(len(findfuncbucket{}.subbuckets)) |
| |
| x := pc - datap.minpc |
| b := x / pcbucketsize |
| i := x % pcbucketsize / (pcbucketsize / nsub) |
| |
| ffb := (*findfuncbucket)(add(unsafe.Pointer(datap.findfunctab), b*unsafe.Sizeof(findfuncbucket{}))) |
| idx := ffb.idx + uint32(ffb.subbuckets[i]) |
| if pc < datap.ftab[idx].entry { |
| throw("findfunc: bad findfunctab entry") |
| } |
| |
| // linear search to find func with pc >= entry. |
| for datap.ftab[idx+1].entry <= pc { |
| idx++ |
| } |
| return (*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[idx].funcoff])) |
| } |
| |
| func pcvalue(f *_func, off int32, targetpc uintptr, strict bool) int32 { |
| if off == 0 { |
| return -1 |
| } |
| datap := findmoduledatap(f.entry) // inefficient |
| p := datap.pclntable[off:] |
| pc := f.entry |
| val := int32(-1) |
| for { |
| var ok bool |
| p, ok = step(p, &pc, &val, pc == f.entry) |
| if !ok { |
| break |
| } |
| if targetpc < pc { |
| return val |
| } |
| } |
| |
| // If there was a table, it should have covered all program counters. |
| // If not, something is wrong. |
| if panicking != 0 || !strict { |
| return -1 |
| } |
| |
| print("runtime: invalid pc-encoded table f=", funcname(f), " pc=", hex(pc), " targetpc=", hex(targetpc), " tab=", p, "\n") |
| |
| p = datap.pclntable[off:] |
| pc = f.entry |
| val = -1 |
| for { |
| var ok bool |
| p, ok = step(p, &pc, &val, pc == f.entry) |
| if !ok { |
| break |
| } |
| print("\tvalue=", val, " until pc=", hex(pc), "\n") |
| } |
| |
| throw("invalid runtime symbol table") |
| return -1 |
| } |
| |
| func cfuncname(f *_func) *byte { |
| if f == nil || f.nameoff == 0 { |
| return nil |
| } |
| datap := findmoduledatap(f.entry) // inefficient |
| return (*byte)(unsafe.Pointer(&datap.pclntable[f.nameoff])) |
| } |
| |
| func funcname(f *_func) string { |
| return gostringnocopy(cfuncname(f)) |
| } |
| |
| func funcline1(f *_func, targetpc uintptr, strict bool) (file string, line int32) { |
| datap := findmoduledatap(f.entry) // inefficient |
| fileno := int(pcvalue(f, f.pcfile, targetpc, strict)) |
| line = pcvalue(f, f.pcln, targetpc, strict) |
| if fileno == -1 || line == -1 || fileno >= len(datap.filetab) { |
| // print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n") |
| return "?", 0 |
| } |
| file = gostringnocopy(&datap.pclntable[datap.filetab[fileno]]) |
| return |
| } |
| |
| func funcline(f *_func, targetpc uintptr) (file string, line int32) { |
| return funcline1(f, targetpc, true) |
| } |
| |
| func funcspdelta(f *_func, targetpc uintptr) int32 { |
| x := pcvalue(f, f.pcsp, targetpc, true) |
| if x&(ptrSize-1) != 0 { |
| print("invalid spdelta ", hex(f.entry), " ", hex(targetpc), " ", hex(f.pcsp), " ", x, "\n") |
| } |
| return x |
| } |
| |
| func pcdatavalue(f *_func, table int32, targetpc uintptr) int32 { |
| if table < 0 || table >= f.npcdata { |
| return -1 |
| } |
| off := *(*int32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4)) |
| return pcvalue(f, off, targetpc, true) |
| } |
| |
| func funcdata(f *_func, i int32) unsafe.Pointer { |
| if i < 0 || i >= f.nfuncdata { |
| return nil |
| } |
| p := add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(f.npcdata)*4) |
| if ptrSize == 8 && uintptr(p)&4 != 0 { |
| if uintptr(unsafe.Pointer(f))&4 != 0 { |
| println("runtime: misaligned func", f) |
| } |
| p = add(p, 4) |
| } |
| return *(*unsafe.Pointer)(add(p, uintptr(i)*ptrSize)) |
| } |
| |
| // step advances to the next pc, value pair in the encoded table. |
| func step(p []byte, pc *uintptr, val *int32, first bool) (newp []byte, ok bool) { |
| p, uvdelta := readvarint(p) |
| if uvdelta == 0 && !first { |
| return nil, false |
| } |
| if uvdelta&1 != 0 { |
| uvdelta = ^(uvdelta >> 1) |
| } else { |
| uvdelta >>= 1 |
| } |
| vdelta := int32(uvdelta) |
| p, pcdelta := readvarint(p) |
| *pc += uintptr(pcdelta * _PCQuantum) |
| *val += vdelta |
| return p, true |
| } |
| |
| // readvarint reads a varint from p. |
| func readvarint(p []byte) (newp []byte, val uint32) { |
| var v, shift uint32 |
| for { |
| b := p[0] |
| p = p[1:] |
| v |= (uint32(b) & 0x7F) << shift |
| if b&0x80 == 0 { |
| break |
| } |
| shift += 7 |
| } |
| return p, v |
| } |
| |
| type stackmap struct { |
| n int32 // number of bitmaps |
| nbit int32 // number of bits in each bitmap |
| bytedata [1]byte // bitmaps, each starting on a 32-bit boundary |
| } |
| |
| //go:nowritebarrier |
| func stackmapdata(stkmap *stackmap, n int32) bitvector { |
| if n < 0 || n >= stkmap.n { |
| throw("stackmapdata: index out of range") |
| } |
| return bitvector{stkmap.nbit, (*byte)(add(unsafe.Pointer(&stkmap.bytedata), uintptr(n*((stkmap.nbit+31)/32*4))))} |
| } |