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// 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
// Frames may be used to get function/file/line information for a
// slice of PC values returned by Callers.
type Frames struct {
// callers is a slice of PCs that have not yet been expanded to frames.
callers []uintptr
// The last PC we saw.
last uintptr
// The number of times we've seen last.
lastCount int
}
// Frame is the information returned by Frames for each call frame.
type Frame struct {
// PC is the program counter for the location in this frame.
// For a frame that calls another frame, this will be the
// program counter of a call instruction. Because of inlining,
// multiple frames may have the same PC value, but different
// symbolic information.
PC uintptr
// Func is the Func value of this call frame. This may be nil
// for non-Go code or fully inlined functions.
Func *Func
// Function is the package path-qualified function name of
// this call frame. If non-empty, this string uniquely
// identifies a single function in the program.
// This may be the empty string if not known.
// If Func is not nil then Function == Func.Name().
Function string
// File and Line are the file name and line number of the
// location in this frame. For non-leaf frames, this will be
// the location of a call. These may be the empty string and
// zero, respectively, if not known.
File string
Line int
// Entry point program counter for the function; may be zero
// if not known. If Func is not nil then Entry ==
// Func.Entry().
Entry uintptr
}
// CallersFrames takes a slice of PC values returned by Callers and
// prepares to return function/file/line information.
// Do not change the slice until you are done with the Frames.
func CallersFrames(callers []uintptr) *Frames {
return &Frames{callers: callers}
}
// Next returns frame information for the next caller.
// If more is false, there are no more callers (the Frame value is valid).
func (ci *Frames) Next() (frame Frame, more bool) {
if len(ci.callers) == 0 {
return Frame{}, false
}
pc := ci.callers[0]
ci.callers = ci.callers[1:]
i := 0
if pc == ci.last {
ci.lastCount++
i = ci.lastCount
} else {
ci.last = pc
ci.lastCount = 0
}
more = len(ci.callers) > 0
// Subtract 1 from PC to undo the 1 we added in callback in
// go-callers.c.
function, file, line, _ := funcfileline(pc-1, int32(i), more)
if function == "" && file == "" {
return Frame{}, more
}
// Demangle function name if needed.
function = demangleSymbol(function)
// Create entry.
entry := funcentry(pc - 1)
f := &Func{name: function, entry: entry}
xpc := pc
if xpc > entry {
xpc--
}
frame = Frame{
PC: xpc,
Func: f,
Function: function,
File: file,
Line: line,
Entry: entry,
}
return frame, more
}
// 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
// or funcInfo() to get the funcInfo instead.
// A Func represents a Go function in the running binary.
type Func struct {
name string
entry uintptr
}
// FuncForPC returns a *Func describing the function that contains the
// given program counter address, or else nil.
//
// If pc represents multiple functions because of inlining, it returns
// the a *Func describing the innermost function, but with an entry
// of the outermost function.
func FuncForPC(pc uintptr) *Func {
name, _, _, _ := funcfileline(pc, -1, false)
if name == "" {
return nil
}
entry := funcentry(pc)
return &Func{name: name, entry: entry}
}
// Name returns the name of the function.
func (f *Func) Name() string {
if f == nil {
return ""
}
return f.name
}
// Entry returns the entry address of the function.
func (f *Func) Entry() uintptr {
if f == nil {
return 0
}
return f.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) {
_, file, line, _ = funcfileline(pc, -1, false)
return file, line
}
func hexval(b byte) uint {
if b >= '0' && b <= '9' {
return uint(b - '0')
}
if b >= 'a' && b <= 'f' {
return uint(b-'a') + 10
}
return 0
}
func hexDigitsToRune(digits []byte, ndig int) rune {
result := uint(0)
for i := 0; i < ndig; i++ {
result <<= uint(4)
result |= hexval(digits[i])
}
return rune(result)
}
// Perform an in-place decoding on the input byte slice. This looks
// for "..z<hex 2 >", "..u<hex x 4>" and "..U<hex x 8>" and overwrites
// with the encoded bytes corresponding to the unicode in question.
// Return value is the number of bytes taken by the result.
func decodeIdentifier(bsl []byte) int {
j := 0
for i := 0; i < len(bsl); i++ {
b := bsl[i]
if i+1 < len(bsl) && bsl[i] == '.' && bsl[i+1] == '.' {
if i+4 < len(bsl) && bsl[i+2] == 'z' {
digits := bsl[i+3:]
r := hexDigitsToRune(digits, 2)
nc := encoderune(bsl[j:], r)
j += nc
i += 4
continue
} else if i+6 < len(bsl) && bsl[i+2] == 'u' {
digits := bsl[i+3:]
r := hexDigitsToRune(digits, 4)
nc := encoderune(bsl[j:], r)
j += nc
i += 6
continue
} else if i+10 < len(bsl) && bsl[i+2] == 'U' {
digits := bsl[i+3:]
r := hexDigitsToRune(digits, 8)
nc := encoderune(bsl[j:], r)
j += nc
i += 10
continue
}
}
bsl[j] = b
j += 1
}
return j
}
// Demangle a function symbol. Applies the reverse of go_encode_id()
// as used in the compiler.
func demangleSymbol(s string) string {
bsl := []byte(s)
nchars := decodeIdentifier(bsl)
bsl = bsl[:nchars]
return string(bsl)
}
// implemented in go-caller.c
func funcfileline(uintptr, int32, bool) (string, string, int, int)
func funcentry(uintptr) uintptr