Source file src/runtime/symtab.go

Documentation: runtime

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  import (
     8  	"runtime/internal/atomic"
     9  	"runtime/internal/sys"
    10  	"unsafe"
    11  )
    12  
    13  // Frames may be used to get function/file/line information for a
    14  // slice of PC values returned by Callers.
    15  type Frames struct {
    16  	// callers is a slice of PCs that have not yet been expanded to frames.
    17  	callers []uintptr
    18  
    19  	// frames is a slice of Frames that have yet to be returned.
    20  	frames     []Frame
    21  	frameStore [2]Frame
    22  }
    23  
    24  // Frame is the information returned by Frames for each call frame.
    25  type Frame struct {
    26  	// PC is the program counter for the location in this frame.
    27  	// For a frame that calls another frame, this will be the
    28  	// program counter of a call instruction. Because of inlining,
    29  	// multiple frames may have the same PC value, but different
    30  	// symbolic information.
    31  	PC uintptr
    32  
    33  	// Func is the Func value of this call frame. This may be nil
    34  	// for non-Go code or fully inlined functions.
    35  	Func *Func
    36  
    37  	// Function is the package path-qualified function name of
    38  	// this call frame. If non-empty, this string uniquely
    39  	// identifies a single function in the program.
    40  	// This may be the empty string if not known.
    41  	// If Func is not nil then Function == Func.Name().
    42  	Function string
    43  
    44  	// File and Line are the file name and line number of the
    45  	// location in this frame. For non-leaf frames, this will be
    46  	// the location of a call. These may be the empty string and
    47  	// zero, respectively, if not known.
    48  	File string
    49  	Line int
    50  
    51  	// Entry point program counter for the function; may be zero
    52  	// if not known. If Func is not nil then Entry ==
    53  	// Func.Entry().
    54  	Entry uintptr
    55  
    56  	// The runtime's internal view of the function. This field
    57  	// is set (funcInfo.valid() returns true) only for Go functions,
    58  	// not for C functions.
    59  	funcInfo funcInfo
    60  }
    61  
    62  // CallersFrames takes a slice of PC values returned by Callers and
    63  // prepares to return function/file/line information.
    64  // Do not change the slice until you are done with the Frames.
    65  func CallersFrames(callers []uintptr) *Frames {
    66  	f := &Frames{callers: callers}
    67  	f.frames = f.frameStore[:0]
    68  	return f
    69  }
    70  
    71  // Next returns frame information for the next caller.
    72  // If more is false, there are no more callers (the Frame value is valid).
    73  func (ci *Frames) Next() (frame Frame, more bool) {
    74  	for len(ci.frames) < 2 {
    75  		// Find the next frame.
    76  		// We need to look for 2 frames so we know what
    77  		// to return for the "more" result.
    78  		if len(ci.callers) == 0 {
    79  			break
    80  		}
    81  		pc := ci.callers[0]
    82  		ci.callers = ci.callers[1:]
    83  		funcInfo := findfunc(pc)
    84  		if !funcInfo.valid() {
    85  			if cgoSymbolizer != nil {
    86  				// Pre-expand cgo frames. We could do this
    87  				// incrementally, too, but there's no way to
    88  				// avoid allocation in this case anyway.
    89  				ci.frames = append(ci.frames, expandCgoFrames(pc)...)
    90  			}
    91  			continue
    92  		}
    93  		f := funcInfo._Func()
    94  		entry := f.Entry()
    95  		if pc > entry {
    96  			// We store the pc of the start of the instruction following
    97  			// the instruction in question (the call or the inline mark).
    98  			// This is done for historical reasons, and to make FuncForPC
    99  			// work correctly for entries in the result of runtime.Callers.
   100  			pc--
   101  		}
   102  		name := funcname(funcInfo)
   103  		if inldata := funcdata(funcInfo, _FUNCDATA_InlTree); inldata != nil {
   104  			inltree := (*[1 << 20]inlinedCall)(inldata)
   105  			ix := pcdatavalue(funcInfo, _PCDATA_InlTreeIndex, pc, nil)
   106  			if ix >= 0 {
   107  				// Note: entry is not modified. It always refers to a real frame, not an inlined one.
   108  				f = nil
   109  				name = funcnameFromNameoff(funcInfo, inltree[ix].func_)
   110  				// File/line is already correct.
   111  				// TODO: remove file/line from InlinedCall?
   112  			}
   113  		}
   114  		ci.frames = append(ci.frames, Frame{
   115  			PC:       pc,
   116  			Func:     f,
   117  			Function: name,
   118  			Entry:    entry,
   119  			funcInfo: funcInfo,
   120  			// Note: File,Line set below
   121  		})
   122  	}
   123  
   124  	// Pop one frame from the frame list. Keep the rest.
   125  	// Avoid allocation in the common case, which is 1 or 2 frames.
   126  	switch len(ci.frames) {
   127  	case 0: // In the rare case when there are no frames at all, we return Frame{}.
   128  		return
   129  	case 1:
   130  		frame = ci.frames[0]
   131  		ci.frames = ci.frameStore[:0]
   132  	case 2:
   133  		frame = ci.frames[0]
   134  		ci.frameStore[0] = ci.frames[1]
   135  		ci.frames = ci.frameStore[:1]
   136  	default:
   137  		frame = ci.frames[0]
   138  		ci.frames = ci.frames[1:]
   139  	}
   140  	more = len(ci.frames) > 0
   141  	if frame.funcInfo.valid() {
   142  		// Compute file/line just before we need to return it,
   143  		// as it can be expensive. This avoids computing file/line
   144  		// for the Frame we find but don't return. See issue 32093.
   145  		file, line := funcline1(frame.funcInfo, frame.PC, false)
   146  		frame.File, frame.Line = file, int(line)
   147  	}
   148  	return
   149  }
   150  
   151  // runtime_expandFinalInlineFrame expands the final pc in stk to include all
   152  // "callers" if pc is inline.
   153  //
   154  //go:linkname runtime_expandFinalInlineFrame runtime/pprof.runtime_expandFinalInlineFrame
   155  func runtime_expandFinalInlineFrame(stk []uintptr) []uintptr {
   156  	if len(stk) == 0 {
   157  		return stk
   158  	}
   159  	pc := stk[len(stk)-1]
   160  	tracepc := pc - 1
   161  
   162  	f := findfunc(tracepc)
   163  	if !f.valid() {
   164  		// Not a Go function.
   165  		return stk
   166  	}
   167  
   168  	inldata := funcdata(f, _FUNCDATA_InlTree)
   169  	if inldata == nil {
   170  		// Nothing inline in f.
   171  		return stk
   172  	}
   173  
   174  	// Treat the previous func as normal. We haven't actually checked, but
   175  	// since this pc was included in the stack, we know it shouldn't be
   176  	// elided.
   177  	lastFuncID := funcID_normal
   178  
   179  	// Remove pc from stk; we'll re-add it below.
   180  	stk = stk[:len(stk)-1]
   181  
   182  	// See inline expansion in gentraceback.
   183  	var cache pcvalueCache
   184  	inltree := (*[1 << 20]inlinedCall)(inldata)
   185  	for {
   186  		ix := pcdatavalue(f, _PCDATA_InlTreeIndex, tracepc, &cache)
   187  		if ix < 0 {
   188  			break
   189  		}
   190  		if inltree[ix].funcID == funcID_wrapper && elideWrapperCalling(lastFuncID) {
   191  			// ignore wrappers
   192  		} else {
   193  			stk = append(stk, pc)
   194  		}
   195  		lastFuncID = inltree[ix].funcID
   196  		// Back up to an instruction in the "caller".
   197  		tracepc = f.entry + uintptr(inltree[ix].parentPc)
   198  		pc = tracepc + 1
   199  	}
   200  
   201  	// N.B. we want to keep the last parentPC which is not inline.
   202  	stk = append(stk, pc)
   203  
   204  	return stk
   205  }
   206  
   207  // expandCgoFrames expands frame information for pc, known to be
   208  // a non-Go function, using the cgoSymbolizer hook. expandCgoFrames
   209  // returns nil if pc could not be expanded.
   210  func expandCgoFrames(pc uintptr) []Frame {
   211  	arg := cgoSymbolizerArg{pc: pc}
   212  	callCgoSymbolizer(&arg)
   213  
   214  	if arg.file == nil && arg.funcName == nil {
   215  		// No useful information from symbolizer.
   216  		return nil
   217  	}
   218  
   219  	var frames []Frame
   220  	for {
   221  		frames = append(frames, Frame{
   222  			PC:       pc,
   223  			Func:     nil,
   224  			Function: gostring(arg.funcName),
   225  			File:     gostring(arg.file),
   226  			Line:     int(arg.lineno),
   227  			Entry:    arg.entry,
   228  			// funcInfo is zero, which implies !funcInfo.valid().
   229  			// That ensures that we use the File/Line info given here.
   230  		})
   231  		if arg.more == 0 {
   232  			break
   233  		}
   234  		callCgoSymbolizer(&arg)
   235  	}
   236  
   237  	// No more frames for this PC. Tell the symbolizer we are done.
   238  	// We don't try to maintain a single cgoSymbolizerArg for the
   239  	// whole use of Frames, because there would be no good way to tell
   240  	// the symbolizer when we are done.
   241  	arg.pc = 0
   242  	callCgoSymbolizer(&arg)
   243  
   244  	return frames
   245  }
   246  
   247  // NOTE: Func does not expose the actual unexported fields, because we return *Func
   248  // values to users, and we want to keep them from being able to overwrite the data
   249  // with (say) *f = Func{}.
   250  // All code operating on a *Func must call raw() to get the *_func
   251  // or funcInfo() to get the funcInfo instead.
   252  
   253  // A Func represents a Go function in the running binary.
   254  type Func struct {
   255  	opaque struct{} // unexported field to disallow conversions
   256  }
   257  
   258  func (f *Func) raw() *_func {
   259  	return (*_func)(unsafe.Pointer(f))
   260  }
   261  
   262  func (f *Func) funcInfo() funcInfo {
   263  	fn := f.raw()
   264  	return funcInfo{fn, findmoduledatap(fn.entry)}
   265  }
   266  
   267  // PCDATA and FUNCDATA table indexes.
   268  //
   269  // See funcdata.h and ../cmd/internal/objabi/funcdata.go.
   270  const (
   271  	_PCDATA_UnsafePoint   = 0
   272  	_PCDATA_StackMapIndex = 1
   273  	_PCDATA_InlTreeIndex  = 2
   274  
   275  	_FUNCDATA_ArgsPointerMaps    = 0
   276  	_FUNCDATA_LocalsPointerMaps  = 1
   277  	_FUNCDATA_StackObjects       = 2
   278  	_FUNCDATA_InlTree            = 3
   279  	_FUNCDATA_OpenCodedDeferInfo = 4
   280  
   281  	_ArgsSizeUnknown = -0x80000000
   282  )
   283  
   284  const (
   285  	// PCDATA_UnsafePoint values.
   286  	_PCDATA_UnsafePointSafe   = -1 // Safe for async preemption
   287  	_PCDATA_UnsafePointUnsafe = -2 // Unsafe for async preemption
   288  
   289  	// _PCDATA_Restart1(2) apply on a sequence of instructions, within
   290  	// which if an async preemption happens, we should back off the PC
   291  	// to the start of the sequence when resume.
   292  	// We need two so we can distinguish the start/end of the sequence
   293  	// in case that two sequences are next to each other.
   294  	_PCDATA_Restart1 = -3
   295  	_PCDATA_Restart2 = -4
   296  
   297  	// Like _PCDATA_RestartAtEntry, but back to function entry if async
   298  	// preempted.
   299  	_PCDATA_RestartAtEntry = -5
   300  )
   301  
   302  // A FuncID identifies particular functions that need to be treated
   303  // specially by the runtime.
   304  // Note that in some situations involving plugins, there may be multiple
   305  // copies of a particular special runtime function.
   306  // Note: this list must match the list in cmd/internal/objabi/funcid.go.
   307  type funcID uint8
   308  
   309  const (
   310  	funcID_normal funcID = iota // not a special function
   311  	funcID_runtime_main
   312  	funcID_goexit
   313  	funcID_jmpdefer
   314  	funcID_mcall
   315  	funcID_morestack
   316  	funcID_mstart
   317  	funcID_rt0_go
   318  	funcID_asmcgocall
   319  	funcID_sigpanic
   320  	funcID_runfinq
   321  	funcID_gcBgMarkWorker
   322  	funcID_systemstack_switch
   323  	funcID_systemstack
   324  	funcID_cgocallback
   325  	funcID_gogo
   326  	funcID_externalthreadhandler
   327  	funcID_debugCallV1
   328  	funcID_gopanic
   329  	funcID_panicwrap
   330  	funcID_handleAsyncEvent
   331  	funcID_asyncPreempt
   332  	funcID_wrapper // any autogenerated code (hash/eq algorithms, method wrappers, etc.)
   333  )
   334  
   335  // pcHeader holds data used by the pclntab lookups.
   336  type pcHeader struct {
   337  	magic          uint32  // 0xFFFFFFFA
   338  	pad1, pad2     uint8   // 0,0
   339  	minLC          uint8   // min instruction size
   340  	ptrSize        uint8   // size of a ptr in bytes
   341  	nfunc          int     // number of functions in the module
   342  	nfiles         uint    // number of entries in the file tab.
   343  	funcnameOffset uintptr // offset to the funcnametab variable from pcHeader
   344  	cuOffset       uintptr // offset to the cutab variable from pcHeader
   345  	filetabOffset  uintptr // offset to the filetab variable from pcHeader
   346  	pctabOffset    uintptr // offset to the pctab varible from pcHeader
   347  	pclnOffset     uintptr // offset to the pclntab variable from pcHeader
   348  }
   349  
   350  // moduledata records information about the layout of the executable
   351  // image. It is written by the linker. Any changes here must be
   352  // matched changes to the code in cmd/internal/ld/symtab.go:symtab.
   353  // moduledata is stored in statically allocated non-pointer memory;
   354  // none of the pointers here are visible to the garbage collector.
   355  type moduledata struct {
   356  	pcHeader     *pcHeader
   357  	funcnametab  []byte
   358  	cutab        []uint32
   359  	filetab      []byte
   360  	pctab        []byte
   361  	pclntable    []byte
   362  	ftab         []functab
   363  	findfunctab  uintptr
   364  	minpc, maxpc uintptr
   365  
   366  	text, etext           uintptr
   367  	noptrdata, enoptrdata uintptr
   368  	data, edata           uintptr
   369  	bss, ebss             uintptr
   370  	noptrbss, enoptrbss   uintptr
   371  	end, gcdata, gcbss    uintptr
   372  	types, etypes         uintptr
   373  
   374  	textsectmap []textsect
   375  	typelinks   []int32 // offsets from types
   376  	itablinks   []*itab
   377  
   378  	ptab []ptabEntry
   379  
   380  	pluginpath string
   381  	pkghashes  []modulehash
   382  
   383  	modulename   string
   384  	modulehashes []modulehash
   385  
   386  	hasmain uint8 // 1 if module contains the main function, 0 otherwise
   387  
   388  	gcdatamask, gcbssmask bitvector
   389  
   390  	typemap map[typeOff]*_type // offset to *_rtype in previous module
   391  
   392  	bad bool // module failed to load and should be ignored
   393  
   394  	next *moduledata
   395  }
   396  
   397  // A modulehash is used to compare the ABI of a new module or a
   398  // package in a new module with the loaded program.
   399  //
   400  // For each shared library a module links against, the linker creates an entry in the
   401  // moduledata.modulehashes slice containing the name of the module, the abi hash seen
   402  // at link time and a pointer to the runtime abi hash. These are checked in
   403  // moduledataverify1 below.
   404  //
   405  // For each loaded plugin, the pkghashes slice has a modulehash of the
   406  // newly loaded package that can be used to check the plugin's version of
   407  // a package against any previously loaded version of the package.
   408  // This is done in plugin.lastmoduleinit.
   409  type modulehash struct {
   410  	modulename   string
   411  	linktimehash string
   412  	runtimehash  *string
   413  }
   414  
   415  // pinnedTypemaps are the map[typeOff]*_type from the moduledata objects.
   416  //
   417  // These typemap objects are allocated at run time on the heap, but the
   418  // only direct reference to them is in the moduledata, created by the
   419  // linker and marked SNOPTRDATA so it is ignored by the GC.
   420  //
   421  // To make sure the map isn't collected, we keep a second reference here.
   422  var pinnedTypemaps []map[typeOff]*_type
   423  
   424  var firstmoduledata moduledata  // linker symbol
   425  var lastmoduledatap *moduledata // linker symbol
   426  var modulesSlice *[]*moduledata // see activeModules
   427  
   428  // activeModules returns a slice of active modules.
   429  //
   430  // A module is active once its gcdatamask and gcbssmask have been
   431  // assembled and it is usable by the GC.
   432  //
   433  // This is nosplit/nowritebarrier because it is called by the
   434  // cgo pointer checking code.
   435  //go:nosplit
   436  //go:nowritebarrier
   437  func activeModules() []*moduledata {
   438  	p := (*[]*moduledata)(atomic.Loadp(unsafe.Pointer(&modulesSlice)))
   439  	if p == nil {
   440  		return nil
   441  	}
   442  	return *p
   443  }
   444  
   445  // modulesinit creates the active modules slice out of all loaded modules.
   446  //
   447  // When a module is first loaded by the dynamic linker, an .init_array
   448  // function (written by cmd/link) is invoked to call addmoduledata,
   449  // appending to the module to the linked list that starts with
   450  // firstmoduledata.
   451  //
   452  // There are two times this can happen in the lifecycle of a Go
   453  // program. First, if compiled with -linkshared, a number of modules
   454  // built with -buildmode=shared can be loaded at program initialization.
   455  // Second, a Go program can load a module while running that was built
   456  // with -buildmode=plugin.
   457  //
   458  // After loading, this function is called which initializes the
   459  // moduledata so it is usable by the GC and creates a new activeModules
   460  // list.
   461  //
   462  // Only one goroutine may call modulesinit at a time.
   463  func modulesinit() {
   464  	modules := new([]*moduledata)
   465  	for md := &firstmoduledata; md != nil; md = md.next {
   466  		if md.bad {
   467  			continue
   468  		}
   469  		*modules = append(*modules, md)
   470  		if md.gcdatamask == (bitvector{}) {
   471  			md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), md.edata-md.data)
   472  			md.gcbssmask = progToPointerMask((*byte)(unsafe.Pointer(md.gcbss)), md.ebss-md.bss)
   473  		}
   474  	}
   475  
   476  	// Modules appear in the moduledata linked list in the order they are
   477  	// loaded by the dynamic loader, with one exception: the
   478  	// firstmoduledata itself the module that contains the runtime. This
   479  	// is not always the first module (when using -buildmode=shared, it
   480  	// is typically libstd.so, the second module). The order matters for
   481  	// typelinksinit, so we swap the first module with whatever module
   482  	// contains the main function.
   483  	//
   484  	// See Issue #18729.
   485  	for i, md := range *modules {
   486  		if md.hasmain != 0 {
   487  			(*modules)[0] = md
   488  			(*modules)[i] = &firstmoduledata
   489  			break
   490  		}
   491  	}
   492  
   493  	atomicstorep(unsafe.Pointer(&modulesSlice), unsafe.Pointer(modules))
   494  }
   495  
   496  type functab struct {
   497  	entry   uintptr
   498  	funcoff uintptr
   499  }
   500  
   501  // Mapping information for secondary text sections
   502  
   503  type textsect struct {
   504  	vaddr    uintptr // prelinked section vaddr
   505  	length   uintptr // section length
   506  	baseaddr uintptr // relocated section address
   507  }
   508  
   509  const minfunc = 16                 // minimum function size
   510  const pcbucketsize = 256 * minfunc // size of bucket in the pc->func lookup table
   511  
   512  // findfunctab is an array of these structures.
   513  // Each bucket represents 4096 bytes of the text segment.
   514  // Each subbucket represents 256 bytes of the text segment.
   515  // To find a function given a pc, locate the bucket and subbucket for
   516  // that pc. Add together the idx and subbucket value to obtain a
   517  // function index. Then scan the functab array starting at that
   518  // index to find the target function.
   519  // This table uses 20 bytes for every 4096 bytes of code, or ~0.5% overhead.
   520  type findfuncbucket struct {
   521  	idx        uint32
   522  	subbuckets [16]byte
   523  }
   524  
   525  func moduledataverify() {
   526  	for datap := &firstmoduledata; datap != nil; datap = datap.next {
   527  		moduledataverify1(datap)
   528  	}
   529  }
   530  
   531  const debugPcln = false
   532  
   533  func moduledataverify1(datap *moduledata) {
   534  	// Check that the pclntab's format is valid.
   535  	hdr := datap.pcHeader
   536  	if hdr.magic != 0xfffffffa || hdr.pad1 != 0 || hdr.pad2 != 0 || hdr.minLC != sys.PCQuantum || hdr.ptrSize != sys.PtrSize {
   537  		println("runtime: function symbol table header:", hex(hdr.magic), hex(hdr.pad1), hex(hdr.pad2), hex(hdr.minLC), hex(hdr.ptrSize))
   538  		throw("invalid function symbol table\n")
   539  	}
   540  
   541  	// ftab is lookup table for function by program counter.
   542  	nftab := len(datap.ftab) - 1
   543  	for i := 0; i < nftab; i++ {
   544  		// NOTE: ftab[nftab].entry is legal; it is the address beyond the final function.
   545  		if datap.ftab[i].entry > datap.ftab[i+1].entry {
   546  			f1 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i].funcoff])), datap}
   547  			f2 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i+1].funcoff])), datap}
   548  			f2name := "end"
   549  			if i+1 < nftab {
   550  				f2name = funcname(f2)
   551  			}
   552  			println("function symbol table not sorted by program counter:", hex(datap.ftab[i].entry), funcname(f1), ">", hex(datap.ftab[i+1].entry), f2name)
   553  			for j := 0; j <= i; j++ {
   554  				print("\t", hex(datap.ftab[j].entry), " ", funcname(funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[j].funcoff])), datap}), "\n")
   555  			}
   556  			if GOOS == "aix" && isarchive {
   557  				println("-Wl,-bnoobjreorder is mandatory on aix/ppc64 with c-archive")
   558  			}
   559  			throw("invalid runtime symbol table")
   560  		}
   561  	}
   562  
   563  	if datap.minpc != datap.ftab[0].entry ||
   564  		datap.maxpc != datap.ftab[nftab].entry {
   565  		throw("minpc or maxpc invalid")
   566  	}
   567  
   568  	for _, modulehash := range datap.modulehashes {
   569  		if modulehash.linktimehash != *modulehash.runtimehash {
   570  			println("abi mismatch detected between", datap.modulename, "and", modulehash.modulename)
   571  			throw("abi mismatch")
   572  		}
   573  	}
   574  }
   575  
   576  // FuncForPC returns a *Func describing the function that contains the
   577  // given program counter address, or else nil.
   578  //
   579  // If pc represents multiple functions because of inlining, it returns
   580  // the *Func describing the innermost function, but with an entry of
   581  // the outermost function.
   582  func FuncForPC(pc uintptr) *Func {
   583  	f := findfunc(pc)
   584  	if !f.valid() {
   585  		return nil
   586  	}
   587  	if inldata := funcdata(f, _FUNCDATA_InlTree); inldata != nil {
   588  		// Note: strict=false so bad PCs (those between functions) don't crash the runtime.
   589  		// We just report the preceding function in that situation. See issue 29735.
   590  		// TODO: Perhaps we should report no function at all in that case.
   591  		// The runtime currently doesn't have function end info, alas.
   592  		if ix := pcdatavalue1(f, _PCDATA_InlTreeIndex, pc, nil, false); ix >= 0 {
   593  			inltree := (*[1 << 20]inlinedCall)(inldata)
   594  			name := funcnameFromNameoff(f, inltree[ix].func_)
   595  			file, line := funcline(f, pc)
   596  			fi := &funcinl{
   597  				entry: f.entry, // entry of the real (the outermost) function.
   598  				name:  name,
   599  				file:  file,
   600  				line:  int(line),
   601  			}
   602  			return (*Func)(unsafe.Pointer(fi))
   603  		}
   604  	}
   605  	return f._Func()
   606  }
   607  
   608  // Name returns the name of the function.
   609  func (f *Func) Name() string {
   610  	if f == nil {
   611  		return ""
   612  	}
   613  	fn := f.raw()
   614  	if fn.entry == 0 { // inlined version
   615  		fi := (*funcinl)(unsafe.Pointer(fn))
   616  		return fi.name
   617  	}
   618  	return funcname(f.funcInfo())
   619  }
   620  
   621  // Entry returns the entry address of the function.
   622  func (f *Func) Entry() uintptr {
   623  	fn := f.raw()
   624  	if fn.entry == 0 { // inlined version
   625  		fi := (*funcinl)(unsafe.Pointer(fn))
   626  		return fi.entry
   627  	}
   628  	return fn.entry
   629  }
   630  
   631  // FileLine returns the file name and line number of the
   632  // source code corresponding to the program counter pc.
   633  // The result will not be accurate if pc is not a program
   634  // counter within f.
   635  func (f *Func) FileLine(pc uintptr) (file string, line int) {
   636  	fn := f.raw()
   637  	if fn.entry == 0 { // inlined version
   638  		fi := (*funcinl)(unsafe.Pointer(fn))
   639  		return fi.file, fi.line
   640  	}
   641  	// Pass strict=false here, because anyone can call this function,
   642  	// and they might just be wrong about targetpc belonging to f.
   643  	file, line32 := funcline1(f.funcInfo(), pc, false)
   644  	return file, int(line32)
   645  }
   646  
   647  func findmoduledatap(pc uintptr) *moduledata {
   648  	for datap := &firstmoduledata; datap != nil; datap = datap.next {
   649  		if datap.minpc <= pc && pc < datap.maxpc {
   650  			return datap
   651  		}
   652  	}
   653  	return nil
   654  }
   655  
   656  type funcInfo struct {
   657  	*_func
   658  	datap *moduledata
   659  }
   660  
   661  func (f funcInfo) valid() bool {
   662  	return f._func != nil
   663  }
   664  
   665  func (f funcInfo) _Func() *Func {
   666  	return (*Func)(unsafe.Pointer(f._func))
   667  }
   668  
   669  func findfunc(pc uintptr) funcInfo {
   670  	datap := findmoduledatap(pc)
   671  	if datap == nil {
   672  		return funcInfo{}
   673  	}
   674  	const nsub = uintptr(len(findfuncbucket{}.subbuckets))
   675  
   676  	x := pc - datap.minpc
   677  	b := x / pcbucketsize
   678  	i := x % pcbucketsize / (pcbucketsize / nsub)
   679  
   680  	ffb := (*findfuncbucket)(add(unsafe.Pointer(datap.findfunctab), b*unsafe.Sizeof(findfuncbucket{})))
   681  	idx := ffb.idx + uint32(ffb.subbuckets[i])
   682  
   683  	// If the idx is beyond the end of the ftab, set it to the end of the table and search backward.
   684  	// This situation can occur if multiple text sections are generated to handle large text sections
   685  	// and the linker has inserted jump tables between them.
   686  
   687  	if idx >= uint32(len(datap.ftab)) {
   688  		idx = uint32(len(datap.ftab) - 1)
   689  	}
   690  	if pc < datap.ftab[idx].entry {
   691  		// With multiple text sections, the idx might reference a function address that
   692  		// is higher than the pc being searched, so search backward until the matching address is found.
   693  
   694  		for datap.ftab[idx].entry > pc && idx > 0 {
   695  			idx--
   696  		}
   697  		if idx == 0 {
   698  			throw("findfunc: bad findfunctab entry idx")
   699  		}
   700  	} else {
   701  		// linear search to find func with pc >= entry.
   702  		for datap.ftab[idx+1].entry <= pc {
   703  			idx++
   704  		}
   705  	}
   706  	funcoff := datap.ftab[idx].funcoff
   707  	if funcoff == ^uintptr(0) {
   708  		// With multiple text sections, there may be functions inserted by the external
   709  		// linker that are not known by Go. This means there may be holes in the PC
   710  		// range covered by the func table. The invalid funcoff value indicates a hole.
   711  		// See also cmd/link/internal/ld/pcln.go:pclntab
   712  		return funcInfo{}
   713  	}
   714  	return funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[funcoff])), datap}
   715  }
   716  
   717  type pcvalueCache struct {
   718  	entries [2][8]pcvalueCacheEnt
   719  }
   720  
   721  type pcvalueCacheEnt struct {
   722  	// targetpc and off together are the key of this cache entry.
   723  	targetpc uintptr
   724  	off      uint32
   725  	// val is the value of this cached pcvalue entry.
   726  	val int32
   727  }
   728  
   729  // pcvalueCacheKey returns the outermost index in a pcvalueCache to use for targetpc.
   730  // It must be very cheap to calculate.
   731  // For now, align to sys.PtrSize and reduce mod the number of entries.
   732  // In practice, this appears to be fairly randomly and evenly distributed.
   733  func pcvalueCacheKey(targetpc uintptr) uintptr {
   734  	return (targetpc / sys.PtrSize) % uintptr(len(pcvalueCache{}.entries))
   735  }
   736  
   737  // Returns the PCData value, and the PC where this value starts.
   738  // TODO: the start PC is returned only when cache is nil.
   739  func pcvalue(f funcInfo, off uint32, targetpc uintptr, cache *pcvalueCache, strict bool) (int32, uintptr) {
   740  	if off == 0 {
   741  		return -1, 0
   742  	}
   743  
   744  	// Check the cache. This speeds up walks of deep stacks, which
   745  	// tend to have the same recursive functions over and over.
   746  	//
   747  	// This cache is small enough that full associativity is
   748  	// cheaper than doing the hashing for a less associative
   749  	// cache.
   750  	if cache != nil {
   751  		x := pcvalueCacheKey(targetpc)
   752  		for i := range cache.entries[x] {
   753  			// We check off first because we're more
   754  			// likely to have multiple entries with
   755  			// different offsets for the same targetpc
   756  			// than the other way around, so we'll usually
   757  			// fail in the first clause.
   758  			ent := &cache.entries[x][i]
   759  			if ent.off == off && ent.targetpc == targetpc {
   760  				return ent.val, 0
   761  			}
   762  		}
   763  	}
   764  
   765  	if !f.valid() {
   766  		if strict && panicking == 0 {
   767  			print("runtime: no module data for ", hex(f.entry), "\n")
   768  			throw("no module data")
   769  		}
   770  		return -1, 0
   771  	}
   772  	datap := f.datap
   773  	p := datap.pctab[off:]
   774  	pc := f.entry
   775  	prevpc := pc
   776  	val := int32(-1)
   777  	for {
   778  		var ok bool
   779  		p, ok = step(p, &pc, &val, pc == f.entry)
   780  		if !ok {
   781  			break
   782  		}
   783  		if targetpc < pc {
   784  			// Replace a random entry in the cache. Random
   785  			// replacement prevents a performance cliff if
   786  			// a recursive stack's cycle is slightly
   787  			// larger than the cache.
   788  			// Put the new element at the beginning,
   789  			// since it is the most likely to be newly used.
   790  			if cache != nil {
   791  				x := pcvalueCacheKey(targetpc)
   792  				e := &cache.entries[x]
   793  				ci := fastrand() % uint32(len(cache.entries[x]))
   794  				e[ci] = e[0]
   795  				e[0] = pcvalueCacheEnt{
   796  					targetpc: targetpc,
   797  					off:      off,
   798  					val:      val,
   799  				}
   800  			}
   801  
   802  			return val, prevpc
   803  		}
   804  		prevpc = pc
   805  	}
   806  
   807  	// If there was a table, it should have covered all program counters.
   808  	// If not, something is wrong.
   809  	if panicking != 0 || !strict {
   810  		return -1, 0
   811  	}
   812  
   813  	print("runtime: invalid pc-encoded table f=", funcname(f), " pc=", hex(pc), " targetpc=", hex(targetpc), " tab=", p, "\n")
   814  
   815  	p = datap.pctab[off:]
   816  	pc = f.entry
   817  	val = -1
   818  	for {
   819  		var ok bool
   820  		p, ok = step(p, &pc, &val, pc == f.entry)
   821  		if !ok {
   822  			break
   823  		}
   824  		print("\tvalue=", val, " until pc=", hex(pc), "\n")
   825  	}
   826  
   827  	throw("invalid runtime symbol table")
   828  	return -1, 0
   829  }
   830  
   831  func cfuncname(f funcInfo) *byte {
   832  	if !f.valid() || f.nameoff == 0 {
   833  		return nil
   834  	}
   835  	return &f.datap.funcnametab[f.nameoff]
   836  }
   837  
   838  func funcname(f funcInfo) string {
   839  	return gostringnocopy(cfuncname(f))
   840  }
   841  
   842  func funcpkgpath(f funcInfo) string {
   843  	name := funcname(f)
   844  	i := len(name) - 1
   845  	for ; i > 0; i-- {
   846  		if name[i] == '/' {
   847  			break
   848  		}
   849  	}
   850  	for ; i < len(name); i++ {
   851  		if name[i] == '.' {
   852  			break
   853  		}
   854  	}
   855  	return name[:i]
   856  }
   857  
   858  func cfuncnameFromNameoff(f funcInfo, nameoff int32) *byte {
   859  	if !f.valid() {
   860  		return nil
   861  	}
   862  	return &f.datap.funcnametab[nameoff]
   863  }
   864  
   865  func funcnameFromNameoff(f funcInfo, nameoff int32) string {
   866  	return gostringnocopy(cfuncnameFromNameoff(f, nameoff))
   867  }
   868  
   869  func funcfile(f funcInfo, fileno int32) string {
   870  	datap := f.datap
   871  	if !f.valid() {
   872  		return "?"
   873  	}
   874  	// Make sure the cu index and file offset are valid
   875  	if fileoff := datap.cutab[f.cuOffset+uint32(fileno)]; fileoff != ^uint32(0) {
   876  		return gostringnocopy(&datap.filetab[fileoff])
   877  	}
   878  	// pcln section is corrupt.
   879  	return "?"
   880  }
   881  
   882  func funcline1(f funcInfo, targetpc uintptr, strict bool) (file string, line int32) {
   883  	datap := f.datap
   884  	if !f.valid() {
   885  		return "?", 0
   886  	}
   887  	fileno, _ := pcvalue(f, f.pcfile, targetpc, nil, strict)
   888  	line, _ = pcvalue(f, f.pcln, targetpc, nil, strict)
   889  	if fileno == -1 || line == -1 || int(fileno) >= len(datap.filetab) {
   890  		// print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n")
   891  		return "?", 0
   892  	}
   893  	file = funcfile(f, fileno)
   894  	return
   895  }
   896  
   897  func funcline(f funcInfo, targetpc uintptr) (file string, line int32) {
   898  	return funcline1(f, targetpc, true)
   899  }
   900  
   901  func funcspdelta(f funcInfo, targetpc uintptr, cache *pcvalueCache) int32 {
   902  	x, _ := pcvalue(f, f.pcsp, targetpc, cache, true)
   903  	if x&(sys.PtrSize-1) != 0 {
   904  		print("invalid spdelta ", funcname(f), " ", hex(f.entry), " ", hex(targetpc), " ", hex(f.pcsp), " ", x, "\n")
   905  	}
   906  	return x
   907  }
   908  
   909  // funcMaxSPDelta returns the maximum spdelta at any point in f.
   910  func funcMaxSPDelta(f funcInfo) int32 {
   911  	datap := f.datap
   912  	p := datap.pctab[f.pcsp:]
   913  	pc := f.entry
   914  	val := int32(-1)
   915  	max := int32(0)
   916  	for {
   917  		var ok bool
   918  		p, ok = step(p, &pc, &val, pc == f.entry)
   919  		if !ok {
   920  			return max
   921  		}
   922  		if val > max {
   923  			max = val
   924  		}
   925  	}
   926  }
   927  
   928  func pcdatastart(f funcInfo, table uint32) uint32 {
   929  	return *(*uint32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4))
   930  }
   931  
   932  func pcdatavalue(f funcInfo, table uint32, targetpc uintptr, cache *pcvalueCache) int32 {
   933  	if table >= f.npcdata {
   934  		return -1
   935  	}
   936  	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, cache, true)
   937  	return r
   938  }
   939  
   940  func pcdatavalue1(f funcInfo, table uint32, targetpc uintptr, cache *pcvalueCache, strict bool) int32 {
   941  	if table >= f.npcdata {
   942  		return -1
   943  	}
   944  	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, cache, strict)
   945  	return r
   946  }
   947  
   948  // Like pcdatavalue, but also return the start PC of this PCData value.
   949  // It doesn't take a cache.
   950  func pcdatavalue2(f funcInfo, table uint32, targetpc uintptr) (int32, uintptr) {
   951  	if table >= f.npcdata {
   952  		return -1, 0
   953  	}
   954  	return pcvalue(f, pcdatastart(f, table), targetpc, nil, true)
   955  }
   956  
   957  func funcdata(f funcInfo, i uint8) unsafe.Pointer {
   958  	if i < 0 || i >= f.nfuncdata {
   959  		return nil
   960  	}
   961  	p := add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(f.npcdata)*4)
   962  	if sys.PtrSize == 8 && uintptr(p)&4 != 0 {
   963  		if uintptr(unsafe.Pointer(f._func))&4 != 0 {
   964  			println("runtime: misaligned func", f._func)
   965  		}
   966  		p = add(p, 4)
   967  	}
   968  	return *(*unsafe.Pointer)(add(p, uintptr(i)*sys.PtrSize))
   969  }
   970  
   971  // step advances to the next pc, value pair in the encoded table.
   972  func step(p []byte, pc *uintptr, val *int32, first bool) (newp []byte, ok bool) {
   973  	// For both uvdelta and pcdelta, the common case (~70%)
   974  	// is that they are a single byte. If so, avoid calling readvarint.
   975  	uvdelta := uint32(p[0])
   976  	if uvdelta == 0 && !first {
   977  		return nil, false
   978  	}
   979  	n := uint32(1)
   980  	if uvdelta&0x80 != 0 {
   981  		n, uvdelta = readvarint(p)
   982  	}
   983  	*val += int32(-(uvdelta & 1) ^ (uvdelta >> 1))
   984  	p = p[n:]
   985  
   986  	pcdelta := uint32(p[0])
   987  	n = 1
   988  	if pcdelta&0x80 != 0 {
   989  		n, pcdelta = readvarint(p)
   990  	}
   991  	p = p[n:]
   992  	*pc += uintptr(pcdelta * sys.PCQuantum)
   993  	return p, true
   994  }
   995  
   996  // readvarint reads a varint from p.
   997  func readvarint(p []byte) (read uint32, val uint32) {
   998  	var v, shift, n uint32
   999  	for {
  1000  		b := p[n]
  1001  		n++
  1002  		v |= uint32(b&0x7F) << (shift & 31)
  1003  		if b&0x80 == 0 {
  1004  			break
  1005  		}
  1006  		shift += 7
  1007  	}
  1008  	return n, v
  1009  }
  1010  
  1011  type stackmap struct {
  1012  	n        int32   // number of bitmaps
  1013  	nbit     int32   // number of bits in each bitmap
  1014  	bytedata [1]byte // bitmaps, each starting on a byte boundary
  1015  }
  1016  
  1017  //go:nowritebarrier
  1018  func stackmapdata(stkmap *stackmap, n int32) bitvector {
  1019  	// Check this invariant only when stackDebug is on at all.
  1020  	// The invariant is already checked by many of stackmapdata's callers,
  1021  	// and disabling it by default allows stackmapdata to be inlined.
  1022  	if stackDebug > 0 && (n < 0 || n >= stkmap.n) {
  1023  		throw("stackmapdata: index out of range")
  1024  	}
  1025  	return bitvector{stkmap.nbit, addb(&stkmap.bytedata[0], uintptr(n*((stkmap.nbit+7)>>3)))}
  1026  }
  1027  
  1028  // inlinedCall is the encoding of entries in the FUNCDATA_InlTree table.
  1029  type inlinedCall struct {
  1030  	parent   int16  // index of parent in the inltree, or < 0
  1031  	funcID   funcID // type of the called function
  1032  	_        byte
  1033  	file     int32 // perCU file index for inlined call. See cmd/link:pcln.go
  1034  	line     int32 // line number of the call site
  1035  	func_    int32 // offset into pclntab for name of called function
  1036  	parentPc int32 // position of an instruction whose source position is the call site (offset from entry)
  1037  }
  1038  

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