74c98bc961
Support for position independent executables (PIE) on the native linux backend, the gdbserver backend on linux and the core backend. Also implemented in the windows native backend, but it can't be tested because go doesn't support PIE on windows yet.
425 lines
11 KiB
Go
425 lines
11 KiB
Go
package frame
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"github.com/derekparker/delve/pkg/dwarf/util"
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)
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type DWRule struct {
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Rule Rule
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Offset int64
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Reg uint64
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Expression []byte
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}
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type FrameContext struct {
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loc uint64
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order binary.ByteOrder
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address uint64
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CFA DWRule
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Regs map[uint64]DWRule
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initialRegs map[uint64]DWRule
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prevRegs map[uint64]DWRule
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buf *bytes.Buffer
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cie *CommonInformationEntry
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RetAddrReg uint64
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codeAlignment uint64
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dataAlignment int64
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}
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// Instructions used to recreate the table from the .debug_frame data.
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const (
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DW_CFA_nop = 0x0 // No ops
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DW_CFA_set_loc = 0x01 // op1: address
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DW_CFA_advance_loc1 = iota // op1: 1-bytes delta
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DW_CFA_advance_loc2 // op1: 2-byte delta
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DW_CFA_advance_loc4 // op1: 4-byte delta
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DW_CFA_offset_extended // op1: ULEB128 register, op2: ULEB128 offset
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DW_CFA_restore_extended // op1: ULEB128 register
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DW_CFA_undefined // op1: ULEB128 register
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DW_CFA_same_value // op1: ULEB128 register
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DW_CFA_register // op1: ULEB128 register, op2: ULEB128 register
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DW_CFA_remember_state // No ops
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DW_CFA_restore_state // No ops
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DW_CFA_def_cfa // op1: ULEB128 register, op2: ULEB128 offset
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DW_CFA_def_cfa_register // op1: ULEB128 register
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DW_CFA_def_cfa_offset // op1: ULEB128 offset
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DW_CFA_def_cfa_expression // op1: BLOCK
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DW_CFA_expression // op1: ULEB128 register, op2: BLOCK
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DW_CFA_offset_extended_sf // op1: ULEB128 register, op2: SLEB128 BLOCK
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DW_CFA_def_cfa_sf // op1: ULEB128 register, op2: SLEB128 offset
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DW_CFA_def_cfa_offset_sf // op1: SLEB128 offset
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DW_CFA_val_offset // op1: ULEB128, op2: ULEB128
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DW_CFA_val_offset_sf // op1: ULEB128, op2: SLEB128
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DW_CFA_val_expression // op1: ULEB128, op2: BLOCK
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DW_CFA_lo_user = 0x1c // op1: BLOCK
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DW_CFA_hi_user = 0x3f // op1: ULEB128 register, op2: BLOCK
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DW_CFA_advance_loc = (0x1 << 6) // High 2 bits: 0x1, low 6: delta
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DW_CFA_offset = (0x2 << 6) // High 2 bits: 0x2, low 6: register
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DW_CFA_restore = (0x3 << 6) // High 2 bits: 0x3, low 6: register
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)
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// Rules defined for register values.
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type Rule byte
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const (
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RuleUndefined Rule = iota
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RuleSameVal
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RuleOffset
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RuleValOffset
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RuleRegister
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RuleExpression
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RuleValExpression
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RuleArchitectural
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RuleCFA // Value is rule.Reg + rule.Offset
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RuleFramePointer // Value is stored at address rule.Reg + rule.Offset, but only if it's less than the current CFA, otherwise same value
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)
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const low_6_offset = 0x3f
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type instruction func(frame *FrameContext)
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// // Mapping from DWARF opcode to function.
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var fnlookup = map[byte]instruction{
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DW_CFA_advance_loc: advanceloc,
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DW_CFA_offset: offset,
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DW_CFA_restore: restore,
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DW_CFA_set_loc: setloc,
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DW_CFA_advance_loc1: advanceloc1,
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DW_CFA_advance_loc2: advanceloc2,
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DW_CFA_advance_loc4: advanceloc4,
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DW_CFA_offset_extended: offsetextended,
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DW_CFA_restore_extended: restoreextended,
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DW_CFA_undefined: undefined,
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DW_CFA_same_value: samevalue,
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DW_CFA_register: register,
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DW_CFA_remember_state: rememberstate,
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DW_CFA_restore_state: restorestate,
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DW_CFA_def_cfa: defcfa,
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DW_CFA_def_cfa_register: defcfaregister,
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DW_CFA_def_cfa_offset: defcfaoffset,
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DW_CFA_def_cfa_expression: defcfaexpression,
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DW_CFA_expression: expression,
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DW_CFA_offset_extended_sf: offsetextendedsf,
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DW_CFA_def_cfa_sf: defcfasf,
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DW_CFA_def_cfa_offset_sf: defcfaoffsetsf,
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DW_CFA_val_offset: valoffset,
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DW_CFA_val_offset_sf: valoffsetsf,
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DW_CFA_val_expression: valexpression,
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DW_CFA_lo_user: louser,
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DW_CFA_hi_user: hiuser,
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}
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func executeCIEInstructions(cie *CommonInformationEntry) *FrameContext {
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initialInstructions := make([]byte, len(cie.InitialInstructions))
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copy(initialInstructions, cie.InitialInstructions)
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frame := &FrameContext{
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cie: cie,
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Regs: make(map[uint64]DWRule),
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RetAddrReg: cie.ReturnAddressRegister,
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initialRegs: make(map[uint64]DWRule),
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prevRegs: make(map[uint64]DWRule),
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codeAlignment: cie.CodeAlignmentFactor,
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dataAlignment: cie.DataAlignmentFactor,
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buf: bytes.NewBuffer(initialInstructions),
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}
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frame.ExecuteDwarfProgram()
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return frame
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}
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// Unwind the stack to find the return address register.
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func executeDwarfProgramUntilPC(fde *FrameDescriptionEntry, pc uint64) *FrameContext {
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frame := executeCIEInstructions(fde.CIE)
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frame.order = fde.order
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frame.loc = fde.Begin()
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frame.address = pc
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frame.ExecuteUntilPC(fde.Instructions)
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return frame
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}
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func (frame *FrameContext) ExecuteDwarfProgram() {
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for frame.buf.Len() > 0 {
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executeDwarfInstruction(frame)
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}
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}
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// Execute dwarf instructions.
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func (frame *FrameContext) ExecuteUntilPC(instructions []byte) {
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frame.buf.Truncate(0)
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frame.buf.Write(instructions)
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// We only need to execute the instructions until
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// ctx.loc > ctx.address (which is the address we
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// are currently at in the traced process).
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for frame.address >= frame.loc && frame.buf.Len() > 0 {
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executeDwarfInstruction(frame)
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}
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}
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func executeDwarfInstruction(frame *FrameContext) {
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instruction, err := frame.buf.ReadByte()
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if err != nil {
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panic("Could not read from instruction buffer")
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}
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if instruction == DW_CFA_nop {
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return
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}
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fn := lookupFunc(instruction, frame.buf)
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fn(frame)
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}
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func lookupFunc(instruction byte, buf *bytes.Buffer) instruction {
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const high_2_bits = 0xc0
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var restore bool
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// Special case the 3 opcodes that have their argument encoded in the opcode itself.
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switch instruction & high_2_bits {
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case DW_CFA_advance_loc:
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instruction = DW_CFA_advance_loc
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restore = true
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case DW_CFA_offset:
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instruction = DW_CFA_offset
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restore = true
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case DW_CFA_restore:
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instruction = DW_CFA_restore
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restore = true
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}
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if restore {
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// Restore the last byte as it actually contains the argument for the opcode.
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err := buf.UnreadByte()
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if err != nil {
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panic("Could not unread byte")
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}
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}
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fn, ok := fnlookup[instruction]
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if !ok {
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panic(fmt.Sprintf("Encountered an unexpected DWARF CFA opcode: %#v", instruction))
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}
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return fn
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}
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func advanceloc(frame *FrameContext) {
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b, err := frame.buf.ReadByte()
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if err != nil {
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panic("Could not read byte")
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}
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delta := b & low_6_offset
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frame.loc += uint64(delta) * frame.codeAlignment
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}
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func advanceloc1(frame *FrameContext) {
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delta, err := frame.buf.ReadByte()
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if err != nil {
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panic("Could not read byte")
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}
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frame.loc += uint64(delta) * frame.codeAlignment
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}
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func advanceloc2(frame *FrameContext) {
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var delta uint16
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binary.Read(frame.buf, frame.order, &delta)
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frame.loc += uint64(delta) * frame.codeAlignment
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}
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func advanceloc4(frame *FrameContext) {
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var delta uint32
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binary.Read(frame.buf, frame.order, &delta)
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frame.loc += uint64(delta) * frame.codeAlignment
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}
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func offset(frame *FrameContext) {
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b, err := frame.buf.ReadByte()
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if err != nil {
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panic(err)
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}
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var (
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reg = b & low_6_offset
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offset, _ = util.DecodeULEB128(frame.buf)
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)
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frame.Regs[uint64(reg)] = DWRule{Offset: int64(offset) * frame.dataAlignment, Rule: RuleOffset}
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}
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func restore(frame *FrameContext) {
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b, err := frame.buf.ReadByte()
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if err != nil {
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panic(err)
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}
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reg := uint64(b & low_6_offset)
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oldrule, ok := frame.initialRegs[reg]
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if ok {
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frame.Regs[reg] = DWRule{Offset: oldrule.Offset, Rule: RuleOffset}
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} else {
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frame.Regs[reg] = DWRule{Rule: RuleUndefined}
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}
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}
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func setloc(frame *FrameContext) {
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var loc uint64
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binary.Read(frame.buf, frame.order, &loc)
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frame.loc = loc + frame.cie.staticBase
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}
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func offsetextended(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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offset, _ = util.DecodeULEB128(frame.buf)
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)
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frame.Regs[reg] = DWRule{Offset: int64(offset) * frame.dataAlignment, Rule: RuleOffset}
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}
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func undefined(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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frame.Regs[reg] = DWRule{Rule: RuleUndefined}
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}
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func samevalue(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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frame.Regs[reg] = DWRule{Rule: RuleSameVal}
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}
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func register(frame *FrameContext) {
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reg1, _ := util.DecodeULEB128(frame.buf)
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reg2, _ := util.DecodeULEB128(frame.buf)
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frame.Regs[reg1] = DWRule{Reg: reg2, Rule: RuleRegister}
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}
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func rememberstate(frame *FrameContext) {
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frame.prevRegs = frame.Regs
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}
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func restorestate(frame *FrameContext) {
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frame.Regs = frame.prevRegs
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}
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func restoreextended(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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oldrule, ok := frame.initialRegs[reg]
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if ok {
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frame.Regs[reg] = DWRule{Offset: oldrule.Offset, Rule: RuleOffset}
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} else {
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frame.Regs[reg] = DWRule{Rule: RuleUndefined}
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}
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}
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func defcfa(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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offset, _ := util.DecodeULEB128(frame.buf)
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frame.CFA.Rule = RuleCFA
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frame.CFA.Reg = reg
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frame.CFA.Offset = int64(offset)
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}
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func defcfaregister(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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frame.CFA.Reg = reg
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}
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func defcfaoffset(frame *FrameContext) {
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offset, _ := util.DecodeULEB128(frame.buf)
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frame.CFA.Offset = int64(offset)
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}
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func defcfasf(frame *FrameContext) {
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reg, _ := util.DecodeULEB128(frame.buf)
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offset, _ := util.DecodeSLEB128(frame.buf)
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frame.CFA.Rule = RuleCFA
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frame.CFA.Reg = reg
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frame.CFA.Offset = offset * frame.dataAlignment
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}
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func defcfaoffsetsf(frame *FrameContext) {
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offset, _ := util.DecodeSLEB128(frame.buf)
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offset *= frame.dataAlignment
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frame.CFA.Offset = offset
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}
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func defcfaexpression(frame *FrameContext) {
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var (
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l, _ = util.DecodeULEB128(frame.buf)
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expr = frame.buf.Next(int(l))
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)
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frame.CFA.Expression = expr
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frame.CFA.Rule = RuleExpression
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}
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func expression(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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l, _ = util.DecodeULEB128(frame.buf)
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expr = frame.buf.Next(int(l))
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)
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frame.Regs[reg] = DWRule{Rule: RuleExpression, Expression: expr}
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}
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func offsetextendedsf(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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offset, _ = util.DecodeSLEB128(frame.buf)
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)
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frame.Regs[reg] = DWRule{Offset: offset * frame.dataAlignment, Rule: RuleOffset}
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}
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func valoffset(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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offset, _ = util.DecodeULEB128(frame.buf)
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)
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frame.Regs[reg] = DWRule{Offset: int64(offset), Rule: RuleValOffset}
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}
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func valoffsetsf(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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offset, _ = util.DecodeSLEB128(frame.buf)
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)
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frame.Regs[reg] = DWRule{Offset: offset * frame.dataAlignment, Rule: RuleValOffset}
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}
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func valexpression(frame *FrameContext) {
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var (
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reg, _ = util.DecodeULEB128(frame.buf)
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l, _ = util.DecodeULEB128(frame.buf)
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expr = frame.buf.Next(int(l))
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)
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frame.Regs[reg] = DWRule{Rule: RuleValExpression, Expression: expr}
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}
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func louser(frame *FrameContext) {
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frame.buf.Next(1)
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}
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func hiuser(frame *FrameContext) {
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frame.buf.Next(1)
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}
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