pkg/cover: provide ReportGenerator.RestorePC

Better encapsulate all of this logic instead of exposing
raw .text offset and a bunch of functions.
Also allows to support gvisor coverage where PCs don't
need to be rewound to previous instruction.

5 files changed, 20 insertions, 13 deletions

diff --git a/pkg/cover/backend/backend.go b/pkg/cover/backend/backend.go
index 7da6abfc5..405cbaa3f 100644
--- a/pkg/cover/backend/backend.go
+++ b/pkg/cover/backend/backend.go
@@ -9,11 +9,11 @@ import (
 )
 
 type Impl struct {
-	Units      []*CompileUnit
-	Symbols    []*Symbol
-	Frames     []symbolizer.Frame
-	TextOffset uint32 // high 32 bits of PCs
-	Symbolize  func(pcs []uint64) ([]symbolizer.Frame, error)
+	Units     []*CompileUnit
+	Symbols   []*Symbol
+	Frames    []symbolizer.Frame
+	Symbolize func(pcs []uint64) ([]symbolizer.Frame, error)
+	RestorePC func(pc uint32) uint64
 }
 
 type CompileUnit struct {
diff --git a/pkg/cover/backend/elf.go b/pkg/cover/backend/elf.go
index 0821f331a..c8e0879b0 100644
--- a/pkg/cover/backend/elf.go
+++ b/pkg/cover/backend/elf.go
@@ -74,12 +74,14 @@ func makeELF(target *targets.Target, objDir string) (*Impl, error) {
 		return nil, fmt.Errorf("failed to parse DWARF (set CONFIG_DEBUG_INFO=y?)")
 	}
 	impl := &Impl{
-		Units:      units,
-		Symbols:    symbols,
-		TextOffset: uint32(textAddr >> 32),
+		Units:   units,
+		Symbols: symbols,
 		Symbolize: func(pcs []uint64) ([]symbolizer.Frame, error) {
 			return symbolize(target, kernelObject, pcs)
 		},
+		RestorePC: func(pc uint32) uint64 {
+			return PreviousInstructionPC(target, RestorePC(pc, uint32(textAddr>>32)))
+		},
 	}
 	return impl, nil
 }
diff --git a/pkg/cover/pc.go b/pkg/cover/backend/pc.go
index 5987e8846..ae92f9298 100644
--- a/pkg/cover/pc.go
+++ b/pkg/cover/backend/pc.go
@@ -1,7 +1,7 @@
 // Copyright 2020 syzkaller project authors. All rights reserved.
 // Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
 
-package cover
+package backend
 
 import (
 	"fmt"
@@ -9,6 +9,10 @@ import (
 	"github.com/google/syzkaller/sys/targets"
 )
 
+func RestorePC(pc, base uint32) uint64 {
+	return uint64(base)<<32 + uint64(pc)
+}
+
 func PreviousInstructionPC(target *targets.Target, pc uint64) uint64 {
 	offset := instructionLen(target.Arch)
 	pc -= offset
diff --git a/pkg/cover/cover.go b/pkg/cover/cover.go
index 40c806fd7..814ae4fb6 100644
--- a/pkg/cover/cover.go
+++ b/pkg/cover/cover.go
@@ -43,7 +43,3 @@ func (cov Cover) Serialize() []uint32 {
 	}
 	return res
 }
-
-func RestorePC(pc, base uint32) uint64 {
-	return uint64(base)<<32 + uint64(pc)
-}
diff --git a/pkg/cover/report.go b/pkg/cover/report.go
index 9b515905f..14c0b7422 100644
--- a/pkg/cover/report.go
+++ b/pkg/cover/report.go
@@ -26,6 +26,11 @@ type Prog struct {
 	PCs  []uint64
 }
 
+var (
+	RestorePC             = backend.RestorePC
+	PreviousInstructionPC = backend.PreviousInstructionPC
+)
+
 func MakeReportGenerator(target *targets.Target, vm, objDir, srcDir, buildDir string) (*ReportGenerator, error) {
 	impl, err := backend.Make(target, vm, objDir)
 	if err != nil {