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cmd/link: make PCIter available to compiler
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I'm branching this off cl/187117, and will be reworking that diff stack.

Testing: I've run go build -toolexec 'toolstash -cmp'

Change-Id: I922a97d0f25d52ea70cd974008a063d4e7af34a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/188023
Reviewed-by: Austin Clements <austin@google.com>
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@jeremyfaller
jeremyfaller committed Sep 23, 2019
1 parent 8b6fa66 commit 8f81625
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Showing 4 changed files with 117 additions and 115 deletions.
66 changes: 66 additions & 0 deletions src/cmd/internal/obj/pcln.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -384,3 +384,69 @@ func linkpcln(ctxt *Link, cursym *LSym) {
}
}
}

// PCIter iterates over encoded pcdata tables.
type PCIter struct {
p []byte
PC uint32
NextPC uint32
PCScale uint32
Value int32
start bool
Done bool
}

// newPCIter creates a PCIter with a scale factor for the PC step size.
func NewPCIter(pcScale uint32) *PCIter {
it := new(PCIter)
it.PCScale = pcScale
return it
}

// Next advances it to the Next pc.
func (it *PCIter) Next() {
it.PC = it.NextPC
if it.Done {
return
}
if len(it.p) == 0 {
it.Done = true
return
}

// Value delta
val, n := binary.Varint(it.p)
if n <= 0 {
log.Fatalf("bad Value varint in pciterNext: read %v", n)
}
it.p = it.p[n:]

if val == 0 && !it.start {
it.Done = true
return
}

it.start = false
it.Value += int32(val)

// pc delta
pc, n := binary.Uvarint(it.p)
if n <= 0 {
log.Fatalf("bad pc varint in pciterNext: read %v", n)
}
it.p = it.p[n:]

it.NextPC = it.PC + uint32(pc)*it.PCScale
}

// init prepares it to iterate over p,
// and advances it to the first pc.
func (it *PCIter) Init(p []byte) {
it.p = p
it.PC = 0
it.NextPC = 0
it.Value = -1
it.start = true
it.Done = false
it.Next()
}
68 changes: 34 additions & 34 deletions src/cmd/link/internal/ld/dwarf.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1212,42 +1212,42 @@ func writelines(ctxt *Link, unit *compilationUnit, ls *sym.Symbol) {
file := 1
ls.AddAddr(ctxt.Arch, s)

pcfile := newPCIter(ctxt)
pcline := newPCIter(ctxt)
pcstmt := newPCIter(ctxt)
pcfile := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
pcline := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
pcstmt := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
for i, s := range unit.lib.Textp {
finddebugruntimepath(s)

pcfile.init(s.FuncInfo.Pcfile.P)
pcline.init(s.FuncInfo.Pcline.P)
pcfile.Init(s.FuncInfo.Pcfile.P)
pcline.Init(s.FuncInfo.Pcline.P)

isStmtSym := dwarfFuncSym(ctxt, s, dwarf.IsStmtPrefix, false)
if isStmtSym != nil && len(isStmtSym.P) > 0 {
pcstmt.init(isStmtSym.P)
pcstmt.Init(isStmtSym.P)
} else {
// Assembly files lack a pcstmt section, we assume that every instruction
// is a valid statement.
pcstmt.done = true
pcstmt.value = 1
pcstmt.Done = true
pcstmt.Value = 1
}

var thispc uint32
// TODO this loop looks like it could exit with work remaining.
for !pcfile.done && !pcline.done {
for !pcfile.Done && !pcline.Done {
// Only changed if it advanced
if int32(file) != pcfile.value {
if int32(file) != pcfile.Value {
ls.AddUint8(dwarf.DW_LNS_set_file)
idx, ok := fileNums[int(pcfile.value)]
idx, ok := fileNums[int(pcfile.Value)]
if !ok {
Exitf("pcln table file missing from DWARF line table")
}
dwarf.Uleb128put(dwarfctxt, ls, int64(idx))
file = int(pcfile.value)
file = int(pcfile.Value)
}

// Only changed if it advanced
if is_stmt != uint8(pcstmt.value) {
new_stmt := uint8(pcstmt.value)
if is_stmt != uint8(pcstmt.Value) {
new_stmt := uint8(pcstmt.Value)
switch new_stmt &^ 1 {
case obj.PrologueEnd:
ls.AddUint8(uint8(dwarf.DW_LNS_set_prologue_end))
Expand All @@ -1263,28 +1263,28 @@ func writelines(ctxt *Link, unit *compilationUnit, ls *sym.Symbol) {
}

// putpcldelta makes a row in the DWARF matrix, always, even if line is unchanged.
putpclcdelta(ctxt, dwarfctxt, ls, uint64(s.Value+int64(thispc)-pc), int64(pcline.value)-int64(line))
putpclcdelta(ctxt, dwarfctxt, ls, uint64(s.Value+int64(thispc)-pc), int64(pcline.Value)-int64(line))

pc = s.Value + int64(thispc)
line = int(pcline.value)
line = int(pcline.Value)

// Take the minimum step forward for the three iterators
thispc = pcfile.nextpc
if pcline.nextpc < thispc {
thispc = pcline.nextpc
thispc = pcfile.NextPC
if pcline.NextPC < thispc {
thispc = pcline.NextPC
}
if !pcstmt.done && pcstmt.nextpc < thispc {
thispc = pcstmt.nextpc
if !pcstmt.Done && pcstmt.NextPC < thispc {
thispc = pcstmt.NextPC
}

if pcfile.nextpc == thispc {
pcfile.next()
if pcfile.NextPC == thispc {
pcfile.Next()
}
if !pcstmt.done && pcstmt.nextpc == thispc {
pcstmt.next()
if !pcstmt.Done && pcstmt.NextPC == thispc {
pcstmt.Next()
}
if pcline.nextpc == thispc {
pcline.next()
if pcline.NextPC == thispc {
pcline.Next()
}
}
if is_stmt == 0 && i < len(unit.lib.Textp)-1 {
Expand Down Expand Up @@ -1451,7 +1451,7 @@ func writeframes(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
fs.AddBytes(zeros[:pad])

var deltaBuf []byte
pcsp := newPCIter(ctxt)
pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
for _, s := range ctxt.Textp {
if s.FuncInfo == nil {
continue
Expand All @@ -1467,19 +1467,19 @@ func writeframes(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
deltaBuf = append(deltaBuf, dwarf.DW_CFA_undefined)
deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(thearch.Dwarfreglr))
}
for pcsp.init(s.FuncInfo.Pcsp.P); !pcsp.done; pcsp.next() {
nextpc := pcsp.nextpc
for pcsp.Init(s.FuncInfo.Pcsp.P); !pcsp.Done; pcsp.Next() {
nextpc := pcsp.NextPC

// pciterinit goes up to the end of the function,
// but DWARF expects us to stop just before the end.
if int64(nextpc) == s.Size {
nextpc--
if nextpc < pcsp.pc {
if nextpc < pcsp.PC {
continue
}
}

spdelta := int64(pcsp.value)
spdelta := int64(pcsp.Value)
if !haslinkregister(ctxt) {
// Return address has been pushed onto stack.
spdelta += int64(ctxt.Arch.PtrSize)
Expand All @@ -1489,7 +1489,7 @@ func writeframes(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
// TODO(bryanpkc): This is imprecise. In general, the instruction
// that stores the return address to the stack frame is not the
// same one that allocates the frame.
if pcsp.value > 0 {
if pcsp.Value > 0 {
// The return address is preserved at (CFA-frame_size)
// after a stack frame has been allocated.
deltaBuf = append(deltaBuf, dwarf.DW_CFA_offset_extended_sf)
Expand All @@ -1503,7 +1503,7 @@ func writeframes(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
}
}

deltaBuf = appendPCDeltaCFA(ctxt.Arch, deltaBuf, int64(nextpc)-int64(pcsp.pc), spdelta)
deltaBuf = appendPCDeltaCFA(ctxt.Arch, deltaBuf, int64(nextpc)-int64(pcsp.PC), spdelta)
}
pad := int(Rnd(int64(len(deltaBuf)), int64(ctxt.Arch.PtrSize))) - len(deltaBuf)
deltaBuf = append(deltaBuf, zeros[:pad]...)
Expand Down
15 changes: 8 additions & 7 deletions src/cmd/link/internal/ld/lib.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ import (
"bufio"
"bytes"
"cmd/internal/bio"
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/loadelf"
Expand Down Expand Up @@ -2137,24 +2138,24 @@ func stkcheck(ctxt *Link, up *chain, depth int) int {

endr := len(s.R)
var ch1 chain
pcsp := newPCIter(ctxt)
pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
var r *sym.Reloc
for pcsp.init(s.FuncInfo.Pcsp.P); !pcsp.done; pcsp.next() {
for pcsp.Init(s.FuncInfo.Pcsp.P); !pcsp.Done; pcsp.Next() {
// pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).

// Check stack size in effect for this span.
if int32(limit)-pcsp.value < 0 {
stkbroke(ctxt, up, int(int32(limit)-pcsp.value))
if int32(limit)-pcsp.Value < 0 {
stkbroke(ctxt, up, int(int32(limit)-pcsp.Value))
return -1
}

// Process calls in this span.
for ; ri < endr && uint32(s.R[ri].Off) < pcsp.nextpc; ri++ {
for ; ri < endr && uint32(s.R[ri].Off) < pcsp.NextPC; ri++ {
r = &s.R[ri]
switch r.Type {
// Direct call.
case objabi.R_CALL, objabi.R_CALLARM, objabi.R_CALLARM64, objabi.R_CALLPOWER, objabi.R_CALLMIPS:
ch.limit = int(int32(limit) - pcsp.value - int32(callsize(ctxt)))
ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
ch.sym = r.Sym
if stkcheck(ctxt, &ch, depth+1) < 0 {
return -1
Expand All @@ -2165,7 +2166,7 @@ func stkcheck(ctxt *Link, up *chain, depth int) int {
// Arrange the data structures to report both calls, so that
// if there is an error, stkprint shows all the steps involved.
case objabi.R_CALLIND:
ch.limit = int(int32(limit) - pcsp.value - int32(callsize(ctxt)))
ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))

ch.sym = nil
ch1.limit = ch.limit - callsize(ctxt) // for morestack in called prologue
Expand Down
83 changes: 9 additions & 74 deletions src/cmd/link/internal/ld/pcln.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
package ld

import (
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/src"
"cmd/internal/sys"
Expand All @@ -16,72 +17,6 @@ import (
"strings"
)

// PCIter iterates over encoded pcdata tables.
type PCIter struct {
p []byte
pc uint32
nextpc uint32
pcscale uint32
value int32
start bool
done bool
}

// newPCIter creates a PCIter and configures it for ctxt's architecture.
func newPCIter(ctxt *Link) *PCIter {
it := new(PCIter)
it.pcscale = uint32(ctxt.Arch.MinLC)
return it
}

// next advances it to the next pc.
func (it *PCIter) next() {
it.pc = it.nextpc
if it.done {
return
}
if len(it.p) == 0 {
it.done = true
return
}

// value delta
val, n := binary.Varint(it.p)
if n <= 0 {
log.Fatalf("bad value varint in pciternext: read %v", n)
}
it.p = it.p[n:]

if val == 0 && !it.start {
it.done = true
return
}

it.start = false
it.value += int32(val)

// pc delta
pc, n := binary.Uvarint(it.p)
if n <= 0 {
log.Fatalf("bad pc varint in pciternext: read %v", n)
}
it.p = it.p[n:]

it.nextpc = it.pc + uint32(pc)*it.pcscale
}

// init prepares it to iterate over p,
// and advances it to the first pc.
func (it *PCIter) init(p []byte) {
it.p = p
it.pc = 0
it.nextpc = 0
it.value = -1
it.start = true
it.done = false
it.next()
}

func ftabaddstring(ftab *sym.Symbol, s string) int32 {
start := len(ftab.P)
ftab.Grow(int64(start + len(s) + 1)) // make room for s plus trailing NUL
Expand Down Expand Up @@ -109,10 +44,10 @@ func renumberfiles(ctxt *Link, files []*sym.Symbol, d *sym.Pcdata) {
buf := make([]byte, binary.MaxVarintLen32)
newval := int32(-1)
var out sym.Pcdata
it := newPCIter(ctxt)
for it.init(d.P); !it.done; it.next() {
it := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
for it.Init(d.P); !it.Done; it.Next() {
// value delta
oldval := it.value
oldval := it.Value

var val int32
if oldval == -1 {
Expand All @@ -132,7 +67,7 @@ func renumberfiles(ctxt *Link, files []*sym.Symbol, d *sym.Pcdata) {
out.P = append(out.P, buf[:n]...)

// pc delta
pc := (it.nextpc - it.pc) / it.pcscale
pc := (it.NextPC - it.PC) / it.PCScale
n = binary.PutUvarint(buf, uint64(pc))
out.P = append(out.P, buf[:n]...)
}
Expand Down Expand Up @@ -337,10 +272,10 @@ func (ctxt *Link) pclntab() {
renumberfiles(ctxt, pcln.File, &pcln.Pcfile)
if false {
// Sanity check the new numbering
it := newPCIter(ctxt)
for it.init(pcln.Pcfile.P); !it.done; it.next() {
if it.value < 1 || it.value > int32(len(ctxt.Filesyms)) {
Errorf(s, "bad file number in pcfile: %d not in range [1, %d]\n", it.value, len(ctxt.Filesyms))
it := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
for it.Init(pcln.Pcfile.P); !it.Done; it.Next() {
if it.Value < 1 || it.Value > int32(len(ctxt.Filesyms)) {
Errorf(s, "bad file number in pcfile: %d not in range [1, %d]\n", it.Value, len(ctxt.Filesyms))
errorexit()
}
}
Expand Down

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