delve/pkg/proc/arch.go

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2015-06-12 19:49:23 +00:00
package proc
import (
"encoding/binary"
"github.com/go-delve/delve/pkg/dwarf/frame"
"github.com/go-delve/delve/pkg/dwarf/op"
"golang.org/x/arch/x86/x86asm"
)
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// Arch defines an interface for representing a
// CPU architecture.
type Arch interface {
PtrSize() int
BreakpointInstruction() []byte
BreakpointSize() int
DerefTLS() bool
FixFrameUnwindContext(fctxt *frame.FrameContext, pc uint64, bi *BinaryInfo) *frame.FrameContext
RegSize(uint64) int
proc: support debugging plugins (#1414) This change splits the BinaryInfo object into a slice of Image objects containing information about the base executable and each loaded shared library (note: go plugins are shared libraries). Delve backens are supposed to call BinaryInfo.AddImage whenever they detect that a new shared library has been loaded. Member fields of BinaryInfo that are used to speed up access to dwarf (Functions, packageVars, consts, etc...) remain part of BinaryInfo and are updated to reference the correct image object. This simplifies this change. This approach has a few shortcomings: 1. Multiple shared libraries can define functions or globals with the same name and we have no way to disambiguate between them. 2. We don't have a way to handle library unloading. Both of those affect C shared libraries much more than they affect go plugins. Go plugins can't be unloaded at all and a lot of name collisions are prevented by import paths. There's only one problem that is concerning: if two plugins both import the same package they will end up with multiple definition for the same function. For example if two plugins use fmt.Printf the final in-memory image (and therefore our BinaryInfo object) will end up with two copies of fmt.Printf at different memory addresses. If a user types break fmt.Printf a breakpoint should be created at *both* locations. Allowing this is a relatively complex change that should be done in a different PR than this. For this reason I consider this approach an acceptable and sustainable stopgap. Updates #865
2019-05-08 21:06:38 +00:00
RegistersToDwarfRegisters(bi *BinaryInfo, regs Registers) op.DwarfRegisters
GoroutineToDwarfRegisters(*G) op.DwarfRegisters
}
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// AMD64 represents the AMD64 CPU architecture.
type AMD64 struct {
ptrSize int
breakInstruction []byte
breakInstructionLen int
gStructOffset uint64
hardwareBreakpointUsage []bool
goos string
// crosscall2fn is the DIE of crosscall2, a function used by the go runtime
// to call C functions. This function in go 1.9 (and previous versions) had
// a bad frame descriptor which needs to be fixed to generate good stack
// traces.
crosscall2fn *Function
// sigreturnfn is the DIE of runtime.sigreturn, the return trampoline for
// the signal handler. See comment in FixFrameUnwindContext for a
// description of why this is needed.
sigreturnfn *Function
}
const (
amd64DwarfIPRegNum uint64 = 16
amd64DwarfSPRegNum uint64 = 7
amd64DwarfBPRegNum uint64 = 6
)
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// AMD64Arch returns an initialized AMD64
// struct.
func AMD64Arch(goos string) *AMD64 {
var breakInstr = []byte{0xCC}
return &AMD64{
ptrSize: 8,
breakInstruction: breakInstr,
breakInstructionLen: len(breakInstr),
hardwareBreakpointUsage: make([]bool, 4),
goos: goos,
}
}
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// PtrSize returns the size of a pointer
// on this architecture.
func (a *AMD64) PtrSize() int {
return a.ptrSize
}
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// BreakpointInstruction returns the Breakpoint
// instruction for this architecture.
func (a *AMD64) BreakpointInstruction() []byte {
return a.breakInstruction
}
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// BreakpointSize returns the size of the
// breakpoint instruction on this architecture.
func (a *AMD64) BreakpointSize() int {
return a.breakInstructionLen
}
// DerefTLS returns true if the value of regs.TLS()+GStructOffset() is a
// pointer to the G struct
func (a *AMD64) DerefTLS() bool {
return a.goos == "windows"
}
const (
crosscall2SPOffsetBad = 0x8
crosscall2SPOffsetWindows = 0x118
crosscall2SPOffsetNonWindows = 0x58
)
// FixFrameUnwindContext adds default architecture rules to fctxt or returns
// the default frame unwind context if fctxt is nil.
func (a *AMD64) FixFrameUnwindContext(fctxt *frame.FrameContext, pc uint64, bi *BinaryInfo) *frame.FrameContext {
if a.sigreturnfn == nil {
a.sigreturnfn = bi.LookupFunc["runtime.sigreturn"]
}
if fctxt == nil || (a.sigreturnfn != nil && pc >= a.sigreturnfn.Entry && pc < a.sigreturnfn.End) {
//if true {
// When there's no frame descriptor entry use BP (the frame pointer) instead
// - return register is [bp + a.PtrSize()] (i.e. [cfa-a.PtrSize()])
// - cfa is bp + a.PtrSize()*2
// - bp is [bp] (i.e. [cfa-a.PtrSize()*2])
// - sp is cfa
// When the signal handler runs it will move the execution to the signal
// handling stack (installed using the sigaltstack system call).
// This isn't a proper stack switch: the pointer to g in TLS will still
// refer to whatever g was executing on that thread before the signal was
// received.
// Since go did not execute a stack switch the previous value of sp, pc
// and bp is not saved inside g.sched, as it normally would.
// The only way to recover is to either read sp/pc from the signal context
// parameter (the ucontext_t* parameter) or to unconditionally follow the
// frame pointer when we get to runtime.sigreturn (which is what we do
// here).
return &frame.FrameContext{
RetAddrReg: amd64DwarfIPRegNum,
Regs: map[uint64]frame.DWRule{
amd64DwarfIPRegNum: frame.DWRule{
Rule: frame.RuleOffset,
Offset: int64(-a.PtrSize()),
},
amd64DwarfBPRegNum: frame.DWRule{
Rule: frame.RuleOffset,
Offset: int64(-2 * a.PtrSize()),
},
amd64DwarfSPRegNum: frame.DWRule{
Rule: frame.RuleValOffset,
Offset: 0,
},
},
CFA: frame.DWRule{
Rule: frame.RuleCFA,
Reg: amd64DwarfBPRegNum,
Offset: int64(2 * a.PtrSize()),
},
}
}
if a.crosscall2fn == nil {
a.crosscall2fn = bi.LookupFunc["crosscall2"]
}
if a.crosscall2fn != nil && pc >= a.crosscall2fn.Entry && pc < a.crosscall2fn.End {
rule := fctxt.CFA
if rule.Offset == crosscall2SPOffsetBad {
switch a.goos {
case "windows":
rule.Offset += crosscall2SPOffsetWindows
default:
rule.Offset += crosscall2SPOffsetNonWindows
}
}
fctxt.CFA = rule
}
// We assume that RBP is the frame pointer and we want to keep it updated,
// so that we can use it to unwind the stack even when we encounter frames
// without descriptor entries.
// If there isn't a rule already we emit one.
if fctxt.Regs[amd64DwarfBPRegNum].Rule == frame.RuleUndefined {
fctxt.Regs[amd64DwarfBPRegNum] = frame.DWRule{
Rule: frame.RuleFramePointer,
Reg: amd64DwarfBPRegNum,
Offset: 0,
}
}
return fctxt
}
// RegSize returns the size (in bytes) of register regnum.
// The mapping between hardware registers and DWARF registers is specified
// in the System V ABI AMD64 Architecture Processor Supplement page 57,
// figure 3.36
// https://www.uclibc.org/docs/psABI-x86_64.pdf
func (a *AMD64) RegSize(regnum uint64) int {
// XMM registers
if regnum > amd64DwarfIPRegNum && regnum <= 32 {
return 16
}
// x87 registers
if regnum >= 33 && regnum <= 40 {
return 10
}
return 8
}
// The mapping between hardware registers and DWARF registers is specified
// in the System V ABI AMD64 Architecture Processor Supplement page 57,
// figure 3.36
// https://www.uclibc.org/docs/psABI-x86_64.pdf
var asm64DwarfToHardware = map[int]x86asm.Reg{
0: x86asm.RAX,
1: x86asm.RDX,
2: x86asm.RCX,
3: x86asm.RBX,
4: x86asm.RSI,
5: x86asm.RDI,
8: x86asm.R8,
9: x86asm.R9,
10: x86asm.R10,
11: x86asm.R11,
12: x86asm.R12,
13: x86asm.R13,
14: x86asm.R14,
15: x86asm.R15,
}
var amd64DwarfToName = map[int]string{
17: "XMM0",
18: "XMM1",
19: "XMM2",
20: "XMM3",
21: "XMM4",
22: "XMM5",
23: "XMM6",
24: "XMM7",
25: "XMM8",
26: "XMM9",
27: "XMM10",
28: "XMM11",
29: "XMM12",
30: "XMM13",
31: "XMM14",
32: "XMM15",
33: "ST(0)",
34: "ST(1)",
35: "ST(2)",
36: "ST(3)",
37: "ST(4)",
38: "ST(5)",
39: "ST(6)",
40: "ST(7)",
49: "Eflags",
50: "Es",
51: "Cs",
52: "Ss",
53: "Ds",
54: "Fs",
55: "Gs",
58: "Fs_base",
59: "Gs_base",
64: "MXCSR",
65: "CW",
66: "SW",
}
func maxAmd64DwarfRegister() int {
max := int(amd64DwarfIPRegNum)
for i := range asm64DwarfToHardware {
if i > max {
max = i
}
}
for i := range amd64DwarfToName {
if i > max {
max = i
}
}
return max
}
// RegistersToDwarfRegisters converts hardware registers to the format used
// by the DWARF expression interpreter.
proc: support debugging plugins (#1414) This change splits the BinaryInfo object into a slice of Image objects containing information about the base executable and each loaded shared library (note: go plugins are shared libraries). Delve backens are supposed to call BinaryInfo.AddImage whenever they detect that a new shared library has been loaded. Member fields of BinaryInfo that are used to speed up access to dwarf (Functions, packageVars, consts, etc...) remain part of BinaryInfo and are updated to reference the correct image object. This simplifies this change. This approach has a few shortcomings: 1. Multiple shared libraries can define functions or globals with the same name and we have no way to disambiguate between them. 2. We don't have a way to handle library unloading. Both of those affect C shared libraries much more than they affect go plugins. Go plugins can't be unloaded at all and a lot of name collisions are prevented by import paths. There's only one problem that is concerning: if two plugins both import the same package they will end up with multiple definition for the same function. For example if two plugins use fmt.Printf the final in-memory image (and therefore our BinaryInfo object) will end up with two copies of fmt.Printf at different memory addresses. If a user types break fmt.Printf a breakpoint should be created at *both* locations. Allowing this is a relatively complex change that should be done in a different PR than this. For this reason I consider this approach an acceptable and sustainable stopgap. Updates #865
2019-05-08 21:06:38 +00:00
func (a *AMD64) RegistersToDwarfRegisters(bi *BinaryInfo, regs Registers) op.DwarfRegisters {
dregs := make([]*op.DwarfRegister, maxAmd64DwarfRegister()+1)
dregs[amd64DwarfIPRegNum] = op.DwarfRegisterFromUint64(regs.PC())
dregs[amd64DwarfSPRegNum] = op.DwarfRegisterFromUint64(regs.SP())
dregs[amd64DwarfBPRegNum] = op.DwarfRegisterFromUint64(regs.BP())
for dwarfReg, asmReg := range asm64DwarfToHardware {
v, err := regs.Get(int(asmReg))
if err == nil {
dregs[dwarfReg] = op.DwarfRegisterFromUint64(v)
}
}
for _, reg := range regs.Slice(true) {
for dwarfReg, regName := range amd64DwarfToName {
if regName == reg.Name {
dregs[dwarfReg] = op.DwarfRegisterFromBytes(reg.Bytes)
}
}
}
proc: support debugging plugins (#1414) This change splits the BinaryInfo object into a slice of Image objects containing information about the base executable and each loaded shared library (note: go plugins are shared libraries). Delve backens are supposed to call BinaryInfo.AddImage whenever they detect that a new shared library has been loaded. Member fields of BinaryInfo that are used to speed up access to dwarf (Functions, packageVars, consts, etc...) remain part of BinaryInfo and are updated to reference the correct image object. This simplifies this change. This approach has a few shortcomings: 1. Multiple shared libraries can define functions or globals with the same name and we have no way to disambiguate between them. 2. We don't have a way to handle library unloading. Both of those affect C shared libraries much more than they affect go plugins. Go plugins can't be unloaded at all and a lot of name collisions are prevented by import paths. There's only one problem that is concerning: if two plugins both import the same package they will end up with multiple definition for the same function. For example if two plugins use fmt.Printf the final in-memory image (and therefore our BinaryInfo object) will end up with two copies of fmt.Printf at different memory addresses. If a user types break fmt.Printf a breakpoint should be created at *both* locations. Allowing this is a relatively complex change that should be done in a different PR than this. For this reason I consider this approach an acceptable and sustainable stopgap. Updates #865
2019-05-08 21:06:38 +00:00
so := bi.pcToImage(regs.PC())
return op.DwarfRegisters{StaticBase: so.StaticBase, Regs: dregs, ByteOrder: binary.LittleEndian, PCRegNum: amd64DwarfIPRegNum, SPRegNum: amd64DwarfSPRegNum, BPRegNum: amd64DwarfBPRegNum}
}
// GoroutineToDwarfRegisters extract the saved DWARF registers from a parked
// goroutine in the format used by the DWARF expression interpreter.
func (a *AMD64) GoroutineToDwarfRegisters(g *G) op.DwarfRegisters {
dregs := make([]*op.DwarfRegister, amd64DwarfIPRegNum+1)
dregs[amd64DwarfIPRegNum] = op.DwarfRegisterFromUint64(g.PC)
dregs[amd64DwarfSPRegNum] = op.DwarfRegisterFromUint64(g.SP)
dregs[amd64DwarfBPRegNum] = op.DwarfRegisterFromUint64(g.BP)
proc: support debugging plugins (#1414) This change splits the BinaryInfo object into a slice of Image objects containing information about the base executable and each loaded shared library (note: go plugins are shared libraries). Delve backens are supposed to call BinaryInfo.AddImage whenever they detect that a new shared library has been loaded. Member fields of BinaryInfo that are used to speed up access to dwarf (Functions, packageVars, consts, etc...) remain part of BinaryInfo and are updated to reference the correct image object. This simplifies this change. This approach has a few shortcomings: 1. Multiple shared libraries can define functions or globals with the same name and we have no way to disambiguate between them. 2. We don't have a way to handle library unloading. Both of those affect C shared libraries much more than they affect go plugins. Go plugins can't be unloaded at all and a lot of name collisions are prevented by import paths. There's only one problem that is concerning: if two plugins both import the same package they will end up with multiple definition for the same function. For example if two plugins use fmt.Printf the final in-memory image (and therefore our BinaryInfo object) will end up with two copies of fmt.Printf at different memory addresses. If a user types break fmt.Printf a breakpoint should be created at *both* locations. Allowing this is a relatively complex change that should be done in a different PR than this. For this reason I consider this approach an acceptable and sustainable stopgap. Updates #865
2019-05-08 21:06:38 +00:00
so := g.variable.bi.pcToImage(g.PC)
return op.DwarfRegisters{StaticBase: so.StaticBase, Regs: dregs, ByteOrder: binary.LittleEndian, PCRegNum: amd64DwarfIPRegNum, SPRegNum: amd64DwarfSPRegNum, BPRegNum: amd64DwarfBPRegNum}
}