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cmd/compile,cmd/link: hooks for identifying coverage counters

Browse source 
Add a new "coverage counter" classification for variables to be used
for storing code coverage counter values (somewhat in the same way
that we identify fuzzer counters). Tagging such variables allows us to
aggregate them in the linker, and to treat updates specially.

Updates #51430.

Change-Id: Ib49fb05736ffece98bcc2f7a7c37e991b7f67bbb
Reviewed-on: https://go-review.googlesource.com/c/go/+/401235
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Than McIntosh 2022-04-19 19:41:40 -04:00
parent 361f5eba9f
commit 072c7d4969
11 changed files with 92 additions and 27 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
src/cmd/compile/internal/gc/obj.go
View file

@ -195,6 +195,9 @@ func dumpGlobal(n *ir.Name) {
}
types.CalcSize(n.Type())
ggloblnod(n)
if n.CoverageCounter() || n.CoverageAuxVar() {
return
}
base.Ctxt.DwarfGlobal(base.Ctxt.Pkgpath, types.TypeSymName(n.Type()), n.Linksym())
}
@ -316,6 +319,9 @@ func ggloblnod(nam *ir.Name) {
if nam.Libfuzzer8BitCounter() {
s.Type = objabi.SLIBFUZZER_8BIT_COUNTER
}
if nam.CoverageCounter() {
s.Type = objabi.SCOVERAGE_COUNTER
}
if nam.Sym().Linkname != "" {
// Make sure linkname'd symbol is non-package. When a symbol is
// both imported and linkname'd, s.Pkg may not set to "_" in

23
src/cmd/compile/internal/inline/inl.go
View file

@ -37,6 +37,7 @@ import (
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/src"
)
@ -471,6 +472,28 @@ func (v *hairyVisitor) doNode(n ir.Node) bool {
}
}
}
case ir.OAS:
// Special case for coverage counter updates and coverage
// function registrations. Although these correspond to real
// operations, we treat them as zero cost for the moment. This
// is primarily due to the existence of tests that are
// sensitive to inlining-- if the insertion of coverage
// instrumentation happens to tip a given function over the
// threshold and move it from "inlinable" to "not-inlinable",
// this can cause changes in allocation behavior, which can
// then result in test failures (a good example is the
// TestAllocations in crypto/ed25519).
n := n.(*ir.AssignStmt)
if n.X.Op() == ir.OINDEX {
n := n.X.(*ir.IndexExpr)
if n.X.Op() == ir.ONAME && n.X.Type().IsArray() {
n := n.X.(*ir.Name)
if n.Linksym().Type == objabi.SCOVERAGE_COUNTER {
return false
}
}
}
}
v.budget--

6
src/cmd/compile/internal/ir/name.go
View file

@ -236,6 +236,8 @@ const (
nameInlLocal // PAUTO created by inliner, derived from callee local
nameOpenDeferSlot // if temporary var storing info for open-coded defers
nameLibfuzzer8BitCounter // if PEXTERN should be assigned to __sancov_cntrs section
nameCoverageCounter // instrumentation counter var for cmd/cover
nameCoverageAuxVar // instrumentation pkg ID variable cmd/cover
nameAlias // is type name an alias
)
@ -251,6 +253,8 @@ func (n *Name) InlFormal() bool { return n.flags&nameInlFormal !=
func (n *Name) InlLocal() bool { return n.flags&nameInlLocal != 0 }
func (n *Name) OpenDeferSlot() bool { return n.flags&nameOpenDeferSlot != 0 }
func (n *Name) Libfuzzer8BitCounter() bool { return n.flags&nameLibfuzzer8BitCounter != 0 }
func (n *Name) CoverageCounter() bool { return n.flags&nameCoverageCounter != 0 }
func (n *Name) CoverageAuxVar() bool { return n.flags&nameCoverageAuxVar != 0 }
func (n *Name) setReadonly(b bool) { n.flags.set(nameReadonly, b) }
func (n *Name) SetNeedzero(b bool) { n.flags.set(nameNeedzero, b) }
@ -264,6 +268,8 @@ func (n *Name) SetInlFormal(b bool) { n.flags.set(nameInlFormal,
func (n *Name) SetInlLocal(b bool) { n.flags.set(nameInlLocal, b) }
func (n *Name) SetOpenDeferSlot(b bool) { n.flags.set(nameOpenDeferSlot, b) }
func (n *Name) SetLibfuzzer8BitCounter(b bool) { n.flags.set(nameLibfuzzer8BitCounter, b) }
func (n *Name) SetCoverageCounter(b bool) { n.flags.set(nameCoverageCounter, b) }
func (n *Name) SetCoverageAuxVar(b bool) { n.flags.set(nameCoverageAuxVar, b) }
// OnStack reports whether variable n may reside on the stack.
func (n *Name) OnStack() bool {

3
src/cmd/compile/internal/ssa/writebarrier.go
View file

@ -652,7 +652,8 @@ func IsSanitizerSafeAddr(v *Value) bool {
// read-only once initialized.
return true
case OpAddr:
return v.Aux.(*obj.LSym).Type == objabi.SRODATA || v.Aux.(*obj.LSym).Type == objabi.SLIBFUZZER_8BIT_COUNTER
vt := v.Aux.(*obj.LSym).Type
return vt == objabi.SRODATA || vt == objabi.SLIBFUZZER_8BIT_COUNTER || vt == objabi.SCOVERAGE_COUNTER || vt == objabi.SCOVERAGE_AUXVAR
}
return false
}

5
src/cmd/internal/objabi/symkind.go
View file

@ -68,6 +68,9 @@ const (
SDWARFLINES
// Coverage instrumentation counter for libfuzzer.
SLIBFUZZER_8BIT_COUNTER
// Update cmd/link/internal/sym/AbiSymKindToSymKind for new SymKind values.
// Coverage instrumentation counter, aux variable for cmd/cover
SCOVERAGE_COUNTER
SCOVERAGE_AUXVAR
// Update cmd/link/internal/sym/AbiSymKindToSymKind for new SymKind values.
)

6
src/cmd/internal/objabi/symkind_string.go
View file

@ -26,11 +26,13 @@ func _() {
_ = x[SDWARFLOC-15]
_ = x[SDWARFLINES-16]
_ = x[SLIBFUZZER_8BIT_COUNTER-17]
_ = x[SCOVERAGE_COUNTER-18]
_ = x[SCOVERAGE_AUXVAR-19]
}
const _SymKind_name = "SxxxSTEXTSRODATASNOPTRDATASDATASBSSSNOPTRBSSSTLSBSSSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSLIBFUZZER_8BIT_COUNTER"
const _SymKind_name = "SxxxSTEXTSRODATASNOPTRDATASDATASBSSSNOPTRBSSSTLSBSSSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVAR"
var _SymKind_index = [...]uint8{0, 4, 9, 16, 26, 31, 35, 44, 51, 63, 74, 83, 95, 105, 114, 125, 134, 145, 168}
var _SymKind_index = [...]uint8{0, 4, 9, 16, 26, 31, 35, 44, 51, 63, 74, 83, 95, 105, 114, 125, 134, 145, 168, 185, 201}
func (i SymKind) String() string {
if i >= SymKind(len(_SymKind_index)-1) {

13
src/cmd/link/internal/ld/data.go
View file

@ -1074,6 +1074,8 @@ func dwarfblk(ctxt *Link, out *OutBuf, addr int64, size int64) {
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, syms, addr, size, zeros[:])
}
var covCounterDataStartOff, covCounterDataLen uint64
var zeros [512]byte
var (
@ -1781,6 +1783,15 @@ func (state *dodataState) allocateDataSections(ctxt *Link) {
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrbss", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.end", 0), sect)
// Code coverage counters are assigned to the .noptrbss section.
// We assign them in a separate pass so that they stay aggregated
// together in a single blob (coverage runtime depends on this).
covCounterDataStartOff = sect.Length
state.assignToSection(sect, sym.SCOVERAGE_COUNTER, sym.SNOPTRBSS)
covCounterDataLen = sect.Length - covCounterDataStartOff
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.covctrs", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.ecovctrs", 0), sect)
// Coverage instrumentation counters for libfuzzer.
if len(state.data[sym.SLIBFUZZER_8BIT_COUNTER]) > 0 {
sect := state.allocateNamedSectionAndAssignSyms(&Segdata, "__sancov_cntrs", sym.SLIBFUZZER_8BIT_COUNTER, sym.Sxxx, 06)
@ -2682,6 +2693,8 @@ func (ctxt *Link) address() []*sym.Segment {
ctxt.xdefine("runtime.edata", sym.SDATA, int64(data.Vaddr+data.Length))
ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr))
ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr+noptrbss.Length))
ctxt.xdefine("runtime.covctrs", sym.SCOVERAGE_COUNTER, int64(noptrbss.Vaddr+covCounterDataStartOff))
ctxt.xdefine("runtime.ecovctrs", sym.SCOVERAGE_COUNTER, int64(noptrbss.Vaddr+covCounterDataStartOff+covCounterDataLen))
ctxt.xdefine("runtime.end", sym.SBSS, int64(Segdata.Vaddr+Segdata.Length))
if fuzzCounters != nil {

6
src/cmd/link/internal/ld/symtab.go
View file

@ -453,6 +453,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
ctxt.xdefine("runtime.ebss", sym.SBSS, 0)
ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, 0)
ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, 0)
ctxt.xdefine("runtime.covctrs", sym.SNOPTRBSS, 0)
ctxt.xdefine("runtime.ecovctrs", sym.SNOPTRBSS, 0)
ctxt.xdefine("runtime.end", sym.SBSS, 0)
ctxt.xdefine("runtime.epclntab", sym.SRODATA, 0)
ctxt.xdefine("runtime.esymtab", sym.SRODATA, 0)
@ -529,7 +531,7 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
nsym := loader.Sym(ldr.NSym())
symGroupType := make([]sym.SymKind, nsym)
for s := loader.Sym(1); s < nsym; s++ {
if !ctxt.IsExternal() && ldr.IsFileLocal(s) && !ldr.IsFromAssembly(s) && ldr.SymPkg(s) != "" {
if (!ctxt.IsExternal() && ldr.IsFileLocal(s) && !ldr.IsFromAssembly(s) && ldr.SymPkg(s) != "") || (ctxt.LinkMode == LinkInternal && ldr.SymType(s) == sym.SCOVERAGE_COUNTER) {
ldr.SetAttrNotInSymbolTable(s, true)
}
if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) || (ldr.SymType(s) != sym.SRODATA && ldr.SymType(s) != sym.SGOFUNC) {
@ -672,6 +674,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ebss", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.noptrbss", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.enoptrbss", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.covctrs", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ecovctrs", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.end", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcdata", 0))
moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcbss", 0))

4
src/cmd/link/internal/sym/symkind.go
View file

@ -98,6 +98,8 @@ const (
SBSS
SNOPTRBSS
SLIBFUZZER_8BIT_COUNTER
SCOVERAGE_COUNTER
SCOVERAGE_AUXVAR
STLSBSS
SXREF
SMACHOSYMSTR
@ -144,6 +146,8 @@ var AbiSymKindToSymKind = [...]SymKind{
objabi.SDWARFLOC: SDWARFLOC,
objabi.SDWARFLINES: SDWARFLINES,
objabi.SLIBFUZZER_8BIT_COUNTER: SLIBFUZZER_8BIT_COUNTER,
objabi.SCOVERAGE_COUNTER: SCOVERAGE_COUNTER,
objabi.SCOVERAGE_AUXVAR: SCOVERAGE_AUXVAR,
}
// ReadOnly are the symbol kinds that form read-only sections. In some

46
src/cmd/link/internal/sym/symkind_string.go
View file

@ -45,31 +45,33 @@ func _() {
_ = x[SBSS-34]
_ = x[SNOPTRBSS-35]
_ = x[SLIBFUZZER_8BIT_COUNTER-36]
_ = x[STLSBSS-37]
_ = x[SXREF-38]
_ = x[SMACHOSYMSTR-39]
_ = x[SMACHOSYMTAB-40]
_ = x[SMACHOINDIRECTPLT-41]
_ = x[SMACHOINDIRECTGOT-42]
_ = x[SFILEPATH-43]
_ = x[SDYNIMPORT-44]
_ = x[SHOSTOBJ-45]
_ = x[SUNDEFEXT-46]
_ = x[SDWARFSECT-47]
_ = x[SDWARFCUINFO-48]
_ = x[SDWARFCONST-49]
_ = x[SDWARFFCN-50]
_ = x[SDWARFABSFCN-51]
_ = x[SDWARFTYPE-52]
_ = x[SDWARFVAR-53]
_ = x[SDWARFRANGE-54]
_ = x[SDWARFLOC-55]
_ = x[SDWARFLINES-56]
_ = x[SCOVERAGE_COUNTER-37]
_ = x[SCOVERAGE_AUXVAR-38]
_ = x[STLSBSS-39]
_ = x[SXREF-40]
_ = x[SMACHOSYMSTR-41]
_ = x[SMACHOSYMTAB-42]
_ = x[SMACHOINDIRECTPLT-43]
_ = x[SMACHOINDIRECTGOT-44]
_ = x[SFILEPATH-45]
_ = x[SDYNIMPORT-46]
_ = x[SHOSTOBJ-47]
_ = x[SUNDEFEXT-48]
_ = x[SDWARFSECT-49]
_ = x[SDWARFCUINFO-50]
_ = x[SDWARFCONST-51]
_ = x[SDWARFFCN-52]
_ = x[SDWARFABSFCN-53]
_ = x[SDWARFTYPE-54]
_ = x[SDWARFVAR-55]
_ = x[SDWARFRANGE-56]
_ = x[SDWARFLOC-57]
_ = x[SDWARFLINES-58]
}
const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINES"
const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINES"
var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 336, 343, 348, 360, 372, 389, 406, 415, 425, 433, 442, 452, 464, 475, 484, 496, 506, 515, 526, 535, 546}
var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 336, 353, 369, 376, 381, 393, 405, 422, 439, 448, 458, 466, 475, 485, 497, 508, 517, 529, 539, 548, 559, 568, 579}
func (i SymKind) String() string {
if i >= SymKind(len(_SymKind_index)-1) {

1
src/runtime/symtab.go
View file

@ -427,6 +427,7 @@ type moduledata struct {
data, edata uintptr
bss, ebss uintptr
noptrbss, enoptrbss uintptr
covctrs, ecovctrs uintptr
end, gcdata, gcbss uintptr
types, etypes uintptr
rodata uintptr