Skip to content

Fix two problems with x86 extraction logic #67

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
brancz merged 1 commit into from
Apr 29, 2025
Merged

Fix two problems with x86 extraction logic #67

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
54 changes: 40 additions & 14 deletions interpreter/luajit/extractor_x86.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -52,12 +52,20 @@ which is a dynamic public symbol that should be in all binaries of LuaJIT includ
func (x *x86Extractor) findOffsetsFromLuaClose(b []byte) (glref, curL uint64, err error) {
b, _ = xh.SkipEndBranch(b)
var greg x86asm.Reg
var zeroReg x86asm.Reg
for len(b) > 0 {
var i x86asm.Inst
i, err = x86asm.Decode(b, 64)
if err != nil {
return 0, 0, err
}
if i.Op == x86asm.XOR {
a0, ok1 := i.Args[0].(x86asm.Reg)
a1, ok2 := i.Args[1].(x86asm.Reg)
if ok1 && ok2 && a0 == a1 {
zeroReg = a0
}
}
if i.Op == x86asm.MOV {
if greg == 0 {
a0, ok1 := i.Args[0].(x86asm.Reg)
Expand All @@ -68,10 +76,17 @@ func (x *x86Extractor) findOffsetsFromLuaClose(b []byte) (glref, curL uint64, er
}
} else {
a0, ok1 := i.Args[0].(x86asm.Mem)
a1, ok2 := i.Args[1].(x86asm.Imm)
if ok1 && ok2 && sameReg(a0.Base, greg) && a1 == 0 {
curL = uint64(a0.Disp)
return glref, curL, nil
if ok1 && sameReg(a0.Base, greg) {
imm, ok2 := i.Args[1].(x86asm.Imm)
if ok2 && imm == 0 {
curL = uint64(a0.Disp)
return glref, curL, nil
}
r1, ok2 := i.Args[1].(x86asm.Reg)
if ok2 && sameReg(r1, zeroReg) {
curL = uint64(a0.Disp)
return glref, curL, nil
}
}
// If Greg is dest error
if r0, ok := i.Args[0].(x86asm.Reg); ok && sameReg(r0, greg) {
Expand All @@ -82,7 +97,7 @@ func (x *x86Extractor) findOffsetsFromLuaClose(b []byte) (glref, curL uint64, er
}
b = b[i.Len:]
}
return 0, 0, errors.New("offsets not found")
return 0, 0, errors.New("find offsets from lua_close failed")
}

// This is different in most builds and we need to get it from stripped binaries.
Expand Down Expand Up @@ -325,8 +340,10 @@ func findRipRelativeLea2ndArgTo2ndCall(b []byte, baseAddr, targetCall int64) (ui
//nolint:gocritic
func skipCallsAABA(b []byte, ip, baseAddr int64) ([]byte, int64, error) {
var lastCall int64
var acall int64
// 3 Step process, 1 is find AA, 2 is find B and 3 is find A.
step := 0
for len(b) > 0 && step < 3 {
for len(b) > 0 {
i, err := x86asm.Decode(b, 64)
if err != nil {
return nil, 0, err
Expand All @@ -335,20 +352,29 @@ func skipCallsAABA(b []byte, ip, baseAddr int64) ([]byte, int64, error) {
a0, ok := i.Args[0].(x86asm.Rel)
if ok {
callAddr := baseAddr + ip + int64(i.Len) + int64(a0)
if lastCall == callAddr {
// Found AA
step++
} else if step > 0 {
step++
if step == 0 && callAddr == lastCall {
// Found potential AA
step = 1
acall = callAddr
} else if step == 1 && callAddr != lastCall {
// Found AAB
step = 2
} else if step == 2 && callAddr == acall {
// Found AABA
step = 3
} else {
// Found different pattern, reset
step = 0
acall = 0
}
lastCall = callAddr
}
}
ip += int64(i.Len)
b = b[i.Len:]
}
if step == 3 {
return b, ip, nil
if step == 3 {
return b, ip, nil
}
}
return nil, 0, errors.New("failed to find AABA call pattern")
}
Expand Down