blob: db20ab11e1e71192b45e8dac6b57132f68466fed [file] [log] [blame]
// 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
)
var (
pclntable []byte
ftab []functab
filetab []uint32
pclntab, epclntab, findfunctab struct{} // linker symbols
minpc, maxpc uintptr
)
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 symtabinit() {
// 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(&pclntab))
pcln32 := (*[2]uint32)(unsafe.Pointer(&pclntab))
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")
}
// pclntable is all bytes of pclntab symbol.
sp := (*sliceStruct)(unsafe.Pointer(&pclntable))
sp.array = unsafe.Pointer(&pclntab)
sp.len = int(uintptr(unsafe.Pointer(&epclntab)) - uintptr(unsafe.Pointer(&pclntab)))
sp.cap = sp.len
// ftab is lookup table for function by program counter.
nftab := int(*(*uintptr)(add(unsafe.Pointer(pcln), 8)))
p := add(unsafe.Pointer(pcln), 8+ptrSize)
sp = (*sliceStruct)(unsafe.Pointer(&ftab))
sp.array = p
sp.len = nftab + 1
sp.cap = sp.len
for i := 0; i < nftab; i++ {
// NOTE: ftab[nftab].entry is legal; it is the address beyond the final function.
if ftab[i].entry > ftab[i+1].entry {
f1 := (*_func)(unsafe.Pointer(&pclntable[ftab[i].funcoff]))
f2 := (*_func)(unsafe.Pointer(&pclntable[ftab[i+1].funcoff]))
f2name := "end"
if i+1 < nftab {
f2name = funcname(f2)
}
println("function symbol table not sorted by program counter:", hex(ftab[i].entry), funcname(f1), ">", hex(ftab[i+1].entry), f2name)
for j := 0; j <= i; j++ {
print("\t", hex(ftab[j].entry), " ", funcname((*_func)(unsafe.Pointer(&pclntable[ftab[j].funcoff]))), "\n")
}
throw("invalid runtime symbol table")
}
}
// The ftab ends with a half functab consisting only of
// 'entry', followed by a uint32 giving the pcln-relative
// offset of the file table.
sp = (*sliceStruct)(unsafe.Pointer(&filetab))
end := unsafe.Pointer(&ftab[nftab].funcoff) // just beyond ftab
fileoffset := *(*uint32)(end)
sp.array = unsafe.Pointer(&pclntable[fileoffset])
// length is in first element of array.
// set len to 1 so we can get first element.
sp.len = 1
sp.cap = 1
sp.len = int(filetab[0])
sp.cap = sp.len
minpc = ftab[0].entry
maxpc = ftab[nftab].entry
}
// 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 findfunc(pc uintptr) *_func {
if pc < minpc || pc >= maxpc {
return nil
}
const nsub = uintptr(len(findfuncbucket{}.subbuckets))
x := pc - minpc
b := x / pcbucketsize
i := x % pcbucketsize / (pcbucketsize/nsub)
ffb := (*findfuncbucket)(add(unsafe.Pointer(&findfunctab), b * unsafe.Sizeof(findfuncbucket{})))
idx := ffb.idx + uint32(ffb.subbuckets[i])
if pc < ftab[idx].entry {
throw("findfunc: bad findfunctab entry")
}
// linear search to find func with pc >= entry.
for ftab[idx+1].entry <= pc {
idx++
}
return (*_func)(unsafe.Pointer(&pclntable[ftab[idx].funcoff]))
}
func pcvalue(f *_func, off int32, targetpc uintptr, strict bool) int32 {
if off == 0 {
return -1
}
p := 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 = 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
}
return (*byte)(unsafe.Pointer(&pclntable[f.nameoff]))
}
func funcname(f *_func) string {
return gostringnocopy(cfuncname(f))
}
func funcline1(f *_func, targetpc uintptr, strict bool) (file string, line int32) {
fileno := int(pcvalue(f, f.pcfile, targetpc, strict))
line = pcvalue(f, f.pcln, targetpc, strict)
if fileno == -1 || line == -1 || fileno >= len(filetab) {
// print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n")
return "?", 0
}
file = gostringnocopy(&pclntable[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
}