internal/coverage/cfile: remove more //go:linkname usage

Move code so that basic imports work instead
of //go:linkname for metadata lists.

For #67401.

Change-Id: Id02075570befc45a9426559aad2137ab540928b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/585915
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

4 files changed, 67 insertions, 23 deletions

diff --git a/src/internal/coverage/cfile/apis.go b/src/internal/coverage/cfile/apis.go
index efae20495b..ef23af0cf1 100644
--- a/src/internal/coverage/cfile/apis.go
+++ b/src/internal/coverage/cfile/apis.go
@@ -7,6 +7,7 @@ package cfile
 import (
 	"fmt"
 	"internal/coverage"
+	"internal/coverage/rtcov"
 	"io"
 	"sync/atomic"
 	"unsafe"
@@ -17,7 +18,7 @@ func WriteMetaDir(dir string) error {
 	if !finalHashComputed {
 		return fmt.Errorf("error: no meta-data available (binary not built with -cover?)")
 	}
-	return emitMetaDataToDirectory(dir, getCovMetaList())
+	return emitMetaDataToDirectory(dir, rtcov.Meta.List)
 }
 
 // WriteMeta implements [runtime/coverage.WriteMeta].
@@ -28,7 +29,7 @@ func WriteMeta(w io.Writer) error {
 	if !finalHashComputed {
 		return fmt.Errorf("error: no meta-data available (binary not built with -cover?)")
 	}
-	ml := getCovMetaList()
+	ml := rtcov.Meta.List
 	return writeMetaData(w, ml, cmode, cgran, finalHash)
 }
 
@@ -57,7 +58,7 @@ func WriteCounters(w io.Writer) error {
 		return fmt.Errorf("meta-data not written yet, unable to write counter data")
 	}
 
-	pm := getCovPkgMap()
+	pm := rtcov.Meta.PkgMap
 	s := &emitState{
 		counterlist: cl,
 		pkgmap:      pm,
diff --git a/src/internal/coverage/cfile/emit.go b/src/internal/coverage/cfile/emit.go
index 68d77c5ae8..3993e9cb42 100644
--- a/src/internal/coverage/cfile/emit.go
+++ b/src/internal/coverage/cfile/emit.go
@@ -29,25 +29,13 @@ import (
 // emitted at the end of code coverage testing runs, from instrumented
 // executables.
 
-// getCovMetaList returns a list of meta-data blobs registered
-// for the currently executing instrumented program. It is defined in the
-// runtime.
-//go:linkname getCovMetaList
-func getCovMetaList() []rtcov.CovMetaBlob
-
 // getCovCounterList returns a list of counter-data blobs registered
 // for the currently executing instrumented program. It is defined in the
 // runtime.
+//
 //go:linkname getCovCounterList
 func getCovCounterList() []rtcov.CovCounterBlob
 
-// getCovPkgMap returns a map storing the remapped package IDs for
-// hard-coded runtime packages (see internal/coverage/pkgid.go for
-// more on why hard-coded package IDs are needed). This function
-// is defined in the runtime.
-//go:linkname getCovPkgMap
-func getCovPkgMap() map[int]int
-
 // emitState holds useful state information during the emit process.
 //
 // When an instrumented program finishes execution and starts the
@@ -180,7 +168,7 @@ func granClash(g coverage.CounterGranularity) bool {
 // all meta-data blobs and capturing os args.
 func prepareForMetaEmit() ([]rtcov.CovMetaBlob, error) {
 	// Ask the runtime for the list of coverage meta-data symbols.
-	ml := getCovMetaList()
+	ml := rtcov.Meta.List
 
 	// In the normal case (go build -o prog.exe ... ; ./prog.exe)
 	// len(ml) will always be non-zero, but we check here since at
@@ -210,7 +198,7 @@ func prepareForMetaEmit() ([]rtcov.CovMetaBlob, error) {
 			}
 			fmt.Fprintf(os.Stderr, "\n")
 		}
-		pm := getCovPkgMap()
+		pm := rtcov.Meta.PkgMap
 		fmt.Fprintf(os.Stderr, "=+= remap table:\n")
 		for from, to := range pm {
 			fmt.Fprintf(os.Stderr, "=+= from %d to %d\n",
@@ -310,7 +298,7 @@ func emitCounterDataToDirectory(outdir string) error {
 	}
 
 	// Ask the runtime for the list of coverage counter symbols.
-	pm := getCovPkgMap()
+	pm := rtcov.Meta.PkgMap
 	s := &emitState{
 		counterlist: cl,
 		pkgmap:      pm,
@@ -591,8 +579,8 @@ func MarkProfileEmitted(val bool) {
 }
 
 func reportErrorInHardcodedList(slot, pkgID int32, fnID, nCtrs uint32) {
-	metaList := getCovMetaList()
-	pkgMap := getCovPkgMap()
+	metaList := rtcov.Meta.List
+	pkgMap := rtcov.Meta.PkgMap
 
 	println("internal error in coverage meta-data tracking:")
 	println("encountered bad pkgID:", pkgID, " at slot:", slot,
diff --git a/src/internal/coverage/cfile/testsupport.go b/src/internal/coverage/cfile/testsupport.go
index 2a64899e28..a5119187a2 100644
--- a/src/internal/coverage/cfile/testsupport.go
+++ b/src/internal/coverage/cfile/testsupport.go
@@ -14,6 +14,7 @@ import (
 	"internal/coverage/decodecounter"
 	"internal/coverage/decodemeta"
 	"internal/coverage/pods"
+	"internal/coverage/rtcov"
 	"internal/runtime/atomic"
 	"io"
 	"os"
@@ -33,7 +34,7 @@ func ProcessCoverTestDir(dir string, cfile string, cm string, cpkg string, w io.
 	}
 
 	// Emit meta-data and counter data.
-	ml := getCovMetaList()
+	ml := rtcov.Meta.List
 	if len(ml) == 0 {
 		// This corresponds to the case where we have a package that
 		// contains test code but no functions (which is fine). In this
diff --git a/src/internal/coverage/rtcov/rtcov.go b/src/internal/coverage/rtcov/rtcov.go
index bbb93acced..9e30d67900 100644
--- a/src/internal/coverage/rtcov/rtcov.go
+++ b/src/internal/coverage/rtcov/rtcov.go
@@ -4,8 +4,10 @@
 
 package rtcov
 
+import "unsafe"
+
 // This package contains types whose structure is shared between
-// the runtime package and the "runtime/coverage" package.
+// the runtime package and the "runtime/coverage" implementation.
 
 // CovMetaBlob is a container for holding the meta-data symbol (an
 // RODATA variable) for an instrumented Go package. Here "p" points to
@@ -32,3 +34,55 @@ type CovCounterBlob struct {
 	Counters *uint32
 	Len      uint64
 }
+
+// Meta is the top-level container for bits of state related to
+// code coverage meta-data in the runtime.
+var Meta struct {
+	// List contains the list of currently registered meta-data
+	// blobs for the running program.
+	List []CovMetaBlob
+
+	// PkgMap records mappings from hard-coded package IDs to
+	// slots in the List above.
+	PkgMap map[int]int
+
+	// Set to true if we discover a package mapping glitch.
+	hardCodedListNeedsUpdating bool
+}
+
+// AddMeta is invoked during package "init" functions by the
+// compiler when compiling for coverage instrumentation; here 'p' is a
+// meta-data blob of length 'dlen' for the package in question, 'hash'
+// is a compiler-computed md5.sum for the blob, 'pkpath' is the
+// package path, 'pkid' is the hard-coded ID that the compiler is
+// using for the package (or -1 if the compiler doesn't think a
+// hard-coded ID is needed), and 'cmode'/'cgran' are the coverage
+// counter mode and granularity requested by the user. Return value is
+// the ID for the package for use by the package code itself,
+// or 0 for impossible errors.
+func AddMeta(p unsafe.Pointer, dlen uint32, hash [16]byte, pkgpath string, pkgid int, cmode uint8, cgran uint8) uint32 {
+	slot := len(Meta.List)
+	Meta.List = append(Meta.List, CovMetaBlob{
+		P:                  (*byte)(p),
+		Len:                dlen,
+		Hash:               hash,
+		PkgPath:            pkgpath,
+		PkgID:              pkgid,
+		CounterMode:        cmode,
+		CounterGranularity: cgran,
+	})
+	if pkgid != -1 {
+		if Meta.PkgMap == nil {
+			Meta.PkgMap = make(map[int]int)
+		}
+		if _, ok := Meta.PkgMap[pkgid]; ok {
+			return 0
+		}
+		// Record the real slot (position on meta-list) for this
+		// package; we'll use the map to fix things up later on.
+		Meta.PkgMap[pkgid] = slot
+	}
+
+	// ID zero is reserved as invalid.
+	return uint32(slot + 1)
+}