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garble/runtime_patch.go

196 lines
4.7 KiB
Go

// Copyright (c) 2020, The Garble Authors.
// See LICENSE for licensing information.
package main
import (
"go/ast"
"go/token"
"strconv"
"strings"
ah "mvdan.cc/garble/internal/asthelper"
)
// updateMagicValue updates hardcoded value of hdr.magic
// when verifying header in symtab.go
func updateMagicValue(file *ast.File, magicValue uint32) {
magicUpdated := false
// Find `hdr.magic != 0xfffffff?` in symtab.go and update to random magicValue
updateMagic := func(node ast.Node) bool {
binExpr, ok := node.(*ast.BinaryExpr)
if !ok || binExpr.Op != token.NEQ {
return true
}
selectorExpr, ok := binExpr.X.(*ast.SelectorExpr)
if !ok {
return true
}
if ident, ok := selectorExpr.X.(*ast.Ident); !ok || ident.Name != "hdr" {
return true
}
if selectorExpr.Sel.Name != "magic" {
return true
}
if _, ok := binExpr.Y.(*ast.BasicLit); !ok {
return true
}
binExpr.Y = &ast.BasicLit{
Kind: token.INT,
Value: strconv.FormatUint(uint64(magicValue), 10),
}
magicUpdated = true
return false
}
for _, decl := range file.Decls {
funcDecl, ok := decl.(*ast.FuncDecl)
if ok && funcDecl.Name.Name == "moduledataverify1" {
ast.Inspect(funcDecl, updateMagic)
break
}
}
if !magicUpdated {
panic("magic value not updated")
}
}
// stripRuntime removes unnecessary code from the runtime,
// such as panic and fatal error printing, and code that
// prints trace/debug info of the runtime.
func stripRuntime(basename string, file *ast.File) {
stripPrints := func(node ast.Node) bool {
call, ok := node.(*ast.CallExpr)
if !ok {
return true
}
id, ok := call.Fun.(*ast.Ident)
if !ok {
return true
}
switch id.Name {
case "print", "println":
id.Name = "hidePrint"
return false
default:
return true
}
}
for _, decl := range file.Decls {
funcDecl, ok := decl.(*ast.FuncDecl)
if !ok {
continue
}
switch basename {
case "error.go":
// only used in panics
switch funcDecl.Name.Name {
case "printany", "printanycustomtype":
funcDecl.Body.List = nil
}
case "mgcscavenge.go":
// used in tracing the scavenger
if funcDecl.Name.Name == "printScavTrace" {
funcDecl.Body.List = nil
}
case "mprof.go":
// remove all functions that print debug/tracing info
// of the runtime
if strings.HasPrefix(funcDecl.Name.Name, "trace") {
funcDecl.Body.List = nil
}
case "panic.go":
// used for printing panics
switch funcDecl.Name.Name {
case "preprintpanics", "printpanics":
funcDecl.Body.List = nil
}
case "print.go":
// only used in tracebacks
if funcDecl.Name.Name == "hexdumpWords" {
funcDecl.Body.List = nil
}
case "proc.go":
// used in tracing the scheduler
if funcDecl.Name.Name == "schedtrace" {
funcDecl.Body.List = nil
}
case "runtime1.go":
usesEnv := func(node ast.Node) bool {
seen := false
ast.Inspect(node, func(node ast.Node) bool {
ident, ok := node.(*ast.Ident)
if ok && ident.Name == "gogetenv" {
seen = true
return false
}
return true
})
return seen
}
filenames:
switch funcDecl.Name.Name {
case "parsedebugvars":
// keep defaults for GODEBUG cgocheck and invalidptr,
// remove code that reads GODEBUG via gogetenv
for i, stmt := range funcDecl.Body.List {
if usesEnv(stmt) {
funcDecl.Body.List = funcDecl.Body.List[:i]
break filenames
}
}
panic("did not see any gogetenv call in parsedebugvars")
case "setTraceback":
// tracebacks are completely hidden, no
// sense keeping this function
funcDecl.Body.List = nil
}
case "traceback.go":
// only used for printing tracebacks
switch funcDecl.Name.Name {
case "tracebackdefers", "printcreatedby", "printcreatedby1", "traceback", "tracebacktrap", "traceback1", "printAncestorTraceback",
"printAncestorTracebackFuncInfo", "goroutineheader", "tracebackothers", "tracebackHexdump", "printCgoTraceback":
funcDecl.Body.List = nil
case "printOneCgoTraceback":
funcDecl.Body = ah.BlockStmt(ah.ReturnStmt(ah.IntLit(0)))
default:
if strings.HasPrefix(funcDecl.Name.Name, "print") {
funcDecl.Body.List = nil
}
}
}
}
if basename == "print.go" {
file.Decls = append(file.Decls, hidePrintDecl)
return
}
// replace all 'print' and 'println' statements in
// the runtime with an empty func, which will be
// optimized out by the compiler
ast.Inspect(file, stripPrints)
}
var hidePrintDecl = &ast.FuncDecl{
Name: ast.NewIdent("hidePrint"),
Type: &ast.FuncType{Params: &ast.FieldList{
List: []*ast.Field{{
Names: []*ast.Ident{{Name: "args"}},
Type: &ast.Ellipsis{Elt: &ast.InterfaceType{
Methods: &ast.FieldList{},
}},
}},
}},
Body: &ast.BlockStmt{},
}