Source file src/runtime/symtab.go

     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  	"internal/abi"
     9  	"internal/goarch"
    10  	"internal/runtime/atomic"
    11  	"internal/runtime/sys"
    12  	"unsafe"
    13  )
    14  
    15  // Frames may be used to get function/file/line information for a
    16  // slice of PC values returned by [Callers].
    17  type Frames struct {
    18  	// callers is a slice of PCs that have not yet been expanded to frames.
    19  	callers []uintptr
    20  
    21  	// nextPC is a next PC to expand ahead of processing callers.
    22  	nextPC uintptr
    23  
    24  	// frames is a slice of Frames that have yet to be returned.
    25  	frames     []Frame
    26  	frameStore [2]Frame
    27  }
    28  
    29  // Frame is the information returned by [Frames] for each call frame.
    30  type Frame struct {
    31  	// PC is the program counter for the location in this frame.
    32  	// For a frame that calls another frame, this will be the
    33  	// program counter of a call instruction. Because of inlining,
    34  	// multiple frames may have the same PC value, but different
    35  	// symbolic information.
    36  	PC uintptr
    37  
    38  	// Func is the Func value of this call frame. This may be nil
    39  	// for non-Go code or fully inlined functions.
    40  	Func *Func
    41  
    42  	// Function is the package path-qualified function name of
    43  	// this call frame. If non-empty, this string uniquely
    44  	// identifies a single function in the program.
    45  	// This may be the empty string if not known.
    46  	// If Func is not nil then Function == Func.Name().
    47  	Function string
    48  
    49  	// File and Line are the file name and line number of the
    50  	// location in this frame. For non-leaf frames, this will be
    51  	// the location of a call. These may be the empty string and
    52  	// zero, respectively, if not known. The file name uses
    53  	// forward slashes, even on Windows.
    54  	File string
    55  	Line int
    56  
    57  	// startLine is the line number of the beginning of the function in
    58  	// this frame. Specifically, it is the line number of the func keyword
    59  	// for Go functions. Note that //line directives can change the
    60  	// filename and/or line number arbitrarily within a function, meaning
    61  	// that the Line - startLine offset is not always meaningful.
    62  	//
    63  	// This may be zero if not known.
    64  	startLine int
    65  
    66  	// Entry point program counter for the function; may be zero
    67  	// if not known. If Func is not nil then Entry ==
    68  	// Func.Entry().
    69  	Entry uintptr
    70  
    71  	// The runtime's internal view of the function. This field
    72  	// is set (funcInfo.valid() returns true) only for Go functions,
    73  	// not for C functions.
    74  	funcInfo funcInfo
    75  }
    76  
    77  // CallersFrames takes a slice of PC values returned by [Callers] and
    78  // prepares to return function/file/line information.
    79  // Do not change the slice until you are done with the [Frames].
    80  func CallersFrames(callers []uintptr) *Frames {
    81  	f := &Frames{callers: callers}
    82  	f.frames = f.frameStore[:0]
    83  	return f
    84  }
    85  
    86  // Next returns a [Frame] representing the next call frame in the slice
    87  // of PC values. If it has already returned all call frames, Next
    88  // returns a zero [Frame].
    89  //
    90  // The more result indicates whether the next call to Next will return
    91  // a valid [Frame]. It does not necessarily indicate whether this call
    92  // returned one.
    93  //
    94  // See the [Frames] example for idiomatic usage.
    95  func (ci *Frames) Next() (frame Frame, more bool) {
    96  	for len(ci.frames) < 2 {
    97  		// Find the next frame.
    98  		// We need to look for 2 frames so we know what
    99  		// to return for the "more" result.
   100  		if len(ci.callers) == 0 {
   101  			break
   102  		}
   103  		var pc uintptr
   104  		if ci.nextPC != 0 {
   105  			pc, ci.nextPC = ci.nextPC, 0
   106  		} else {
   107  			pc, ci.callers = ci.callers[0], ci.callers[1:]
   108  		}
   109  		funcInfo := findfunc(pc)
   110  		if !funcInfo.valid() {
   111  			if cgoSymbolizerAvailable() {
   112  				// Pre-expand cgo frames. We could do this
   113  				// incrementally, too, but there's no way to
   114  				// avoid allocation in this case anyway.
   115  				ci.frames = append(ci.frames, expandCgoFrames(pc)...)
   116  			}
   117  			continue
   118  		}
   119  		f := funcInfo._Func()
   120  		entry := f.Entry()
   121  		// We store the pc of the start of the instruction following
   122  		// the instruction in question (the call or the inline mark).
   123  		// This is done for historical reasons, and to make FuncForPC
   124  		// work correctly for entries in the result of runtime.Callers.
   125  		// Decrement to get back to the instruction we care about.
   126  		//
   127  		// It is not possible to get pc == entry from runtime.Callers,
   128  		// but if the caller does provide one, provide best-effort
   129  		// results by avoiding backing out of the function entirely.
   130  		if pc > entry {
   131  			pc--
   132  		}
   133  		// It's important that interpret pc non-strictly as cgoTraceback may
   134  		// have added bogus PCs with a valid funcInfo but invalid PCDATA.
   135  		u, uf := newInlineUnwinder(funcInfo, pc)
   136  		sf := u.srcFunc(uf)
   137  		if u.isInlined(uf) {
   138  			// Note: entry is not modified. It always refers to a real frame, not an inlined one.
   139  			// File/line from funcline1 below are already correct.
   140  			f = nil
   141  
   142  			// When CallersFrame is invoked using the PC list returned by Callers,
   143  			// the PC list includes virtual PCs corresponding to each outer frame
   144  			// around an innermost real inlined PC.
   145  			// We also want to support code passing in a PC list extracted from a
   146  			// stack trace, and there only the real PCs are printed, not the virtual ones.
   147  			// So check to see if the implied virtual PC for this PC (obtained from the
   148  			// unwinder itself) is the next PC in ci.callers. If not, insert it.
   149  			// The +1 here correspond to the pc-- above: the output of Callers
   150  			// and therefore the input to CallersFrames is return PCs from the stack;
   151  			// The pc-- backs up into the CALL instruction (not the first byte of the CALL
   152  			// instruction, but good enough to find it nonetheless).
   153  			// There are no cycles in implied virtual PCs (some number of frames were
   154  			// inlined, but that number is finite), so this unpacking cannot cause an infinite loop.
   155  			for unext := u.next(uf); unext.valid() && len(ci.callers) > 0 && ci.callers[0] != unext.pc+1; unext = u.next(unext) {
   156  				snext := u.srcFunc(unext)
   157  				if snext.funcID == abi.FuncIDWrapper && elideWrapperCalling(sf.funcID) {
   158  					// Skip, because tracebackPCs (inside runtime.Callers) would too.
   159  					continue
   160  				}
   161  				ci.nextPC = unext.pc + 1
   162  				break
   163  			}
   164  		}
   165  		ci.frames = append(ci.frames, Frame{
   166  			PC:        pc,
   167  			Func:      f,
   168  			Function:  funcNameForPrint(sf.name()),
   169  			Entry:     entry,
   170  			startLine: int(sf.startLine),
   171  			funcInfo:  funcInfo,
   172  			// Note: File,Line set below
   173  		})
   174  	}
   175  
   176  	// Pop one frame from the frame list. Keep the rest.
   177  	// Avoid allocation in the common case, which is 1 or 2 frames.
   178  	switch len(ci.frames) {
   179  	case 0: // In the rare case when there are no frames at all, we return Frame{}.
   180  		return
   181  	case 1:
   182  		frame = ci.frames[0]
   183  		ci.frames = ci.frameStore[:0]
   184  	case 2:
   185  		frame = ci.frames[0]
   186  		ci.frameStore[0] = ci.frames[1]
   187  		ci.frames = ci.frameStore[:1]
   188  	default:
   189  		frame = ci.frames[0]
   190  		ci.frames = ci.frames[1:]
   191  	}
   192  	more = len(ci.frames) > 0
   193  	if frame.funcInfo.valid() {
   194  		// Compute file/line just before we need to return it,
   195  		// as it can be expensive. This avoids computing file/line
   196  		// for the Frame we find but don't return. See issue 32093.
   197  		file, line := funcline1(frame.funcInfo, frame.PC, false)
   198  		frame.File, frame.Line = file, int(line)
   199  	}
   200  	return
   201  }
   202  
   203  // runtime_FrameStartLine returns the start line of the function in a Frame.
   204  //
   205  // runtime_FrameStartLine should be an internal detail,
   206  // but widely used packages access it using linkname.
   207  // Notable members of the hall of shame include:
   208  //   - github.com/grafana/pyroscope-go/godeltaprof
   209  //
   210  // Do not remove or change the type signature.
   211  // See go.dev/issue/67401.
   212  //
   213  //go:linkname runtime_FrameStartLine runtime/pprof.runtime_FrameStartLine
   214  func runtime_FrameStartLine(f *Frame) int {
   215  	return f.startLine
   216  }
   217  
   218  // runtime_FrameSymbolName returns the full symbol name of the function in a Frame.
   219  // For generic functions this differs from f.Function in that this doesn't replace
   220  // the shape name to "...".
   221  //
   222  // runtime_FrameSymbolName should be an internal detail,
   223  // but widely used packages access it using linkname.
   224  // Notable members of the hall of shame include:
   225  //   - github.com/grafana/pyroscope-go/godeltaprof
   226  //
   227  // Do not remove or change the type signature.
   228  // See go.dev/issue/67401.
   229  //
   230  //go:linkname runtime_FrameSymbolName runtime/pprof.runtime_FrameSymbolName
   231  func runtime_FrameSymbolName(f *Frame) string {
   232  	if !f.funcInfo.valid() {
   233  		return f.Function
   234  	}
   235  	u, uf := newInlineUnwinder(f.funcInfo, f.PC)
   236  	sf := u.srcFunc(uf)
   237  	return sf.name()
   238  }
   239  
   240  // runtime_expandFinalInlineFrame expands the final pc in stk to include all
   241  // "callers" if pc is inline.
   242  //
   243  // runtime_expandFinalInlineFrame should be an internal detail,
   244  // but widely used packages access it using linkname.
   245  // Notable members of the hall of shame include:
   246  //   - github.com/grafana/pyroscope-go/godeltaprof
   247  //   - github.com/pyroscope-io/godeltaprof
   248  //
   249  // Do not remove or change the type signature.
   250  // See go.dev/issue/67401.
   251  //
   252  //go:linkname runtime_expandFinalInlineFrame runtime/pprof.runtime_expandFinalInlineFrame
   253  func runtime_expandFinalInlineFrame(stk []uintptr) []uintptr {
   254  	// TODO: It would be more efficient to report only physical PCs to pprof and
   255  	// just expand the whole stack.
   256  	if len(stk) == 0 {
   257  		return stk
   258  	}
   259  	pc := stk[len(stk)-1]
   260  	tracepc := pc - 1
   261  
   262  	f := findfunc(tracepc)
   263  	if !f.valid() {
   264  		// Not a Go function.
   265  		return stk
   266  	}
   267  
   268  	u, uf := newInlineUnwinder(f, tracepc)
   269  	if !u.isInlined(uf) {
   270  		// Nothing inline at tracepc.
   271  		return stk
   272  	}
   273  
   274  	// Treat the previous func as normal. We haven't actually checked, but
   275  	// since this pc was included in the stack, we know it shouldn't be
   276  	// elided.
   277  	calleeID := abi.FuncIDNormal
   278  
   279  	// Remove pc from stk; we'll re-add it below.
   280  	stk = stk[:len(stk)-1]
   281  
   282  	for ; uf.valid(); uf = u.next(uf) {
   283  		funcID := u.srcFunc(uf).funcID
   284  		if funcID == abi.FuncIDWrapper && elideWrapperCalling(calleeID) {
   285  			// ignore wrappers
   286  		} else {
   287  			stk = append(stk, uf.pc+1)
   288  		}
   289  		calleeID = funcID
   290  	}
   291  
   292  	return stk
   293  }
   294  
   295  // expandCgoFrames expands frame information for pc, known to be
   296  // a non-Go function, using the cgoSymbolizer hook. expandCgoFrames
   297  // returns nil if pc could not be expanded.
   298  //
   299  // Preconditions: cgoSymbolizerAvailable returns true.
   300  func expandCgoFrames(pc uintptr) []Frame {
   301  	arg := cgoSymbolizerArg{pc: pc}
   302  	callCgoSymbolizer(&arg)
   303  
   304  	if arg.file == nil && arg.funcName == nil {
   305  		// No useful information from symbolizer.
   306  		return nil
   307  	}
   308  
   309  	var frames []Frame
   310  	for {
   311  		frames = append(frames, Frame{
   312  			PC:       pc,
   313  			Func:     nil,
   314  			Function: gostring(arg.funcName),
   315  			File:     gostring(arg.file),
   316  			Line:     int(arg.lineno),
   317  			Entry:    arg.entry,
   318  			// funcInfo is zero, which implies !funcInfo.valid().
   319  			// That ensures that we use the File/Line info given here.
   320  		})
   321  		if arg.more == 0 {
   322  			break
   323  		}
   324  		callCgoSymbolizer(&arg)
   325  	}
   326  
   327  	// No more frames for this PC. Tell the symbolizer we are done.
   328  	// We don't try to maintain a single cgoSymbolizerArg for the
   329  	// whole use of Frames, because there would be no good way to tell
   330  	// the symbolizer when we are done.
   331  	arg.pc = 0
   332  	callCgoSymbolizer(&arg)
   333  
   334  	return frames
   335  }
   336  
   337  // NOTE: Func does not expose the actual unexported fields, because we return *Func
   338  // values to users, and we want to keep them from being able to overwrite the data
   339  // with (say) *f = Func{}.
   340  // All code operating on a *Func must call raw() to get the *_func
   341  // or funcInfo() to get the funcInfo instead.
   342  
   343  // A Func represents a Go function in the running binary.
   344  type Func struct {
   345  	opaque struct{} // unexported field to disallow conversions
   346  }
   347  
   348  func (f *Func) raw() *_func {
   349  	return (*_func)(unsafe.Pointer(f))
   350  }
   351  
   352  func (f *Func) funcInfo() funcInfo {
   353  	return f.raw().funcInfo()
   354  }
   355  
   356  func (f *_func) funcInfo() funcInfo {
   357  	// Find the module containing fn. fn is located in the pclntable.
   358  	// The unsafe.Pointer to uintptr conversions and arithmetic
   359  	// are safe because we are working with module addresses.
   360  	ptr := uintptr(unsafe.Pointer(f))
   361  	var mod *moduledata
   362  	for datap := &firstmoduledata; datap != nil; datap = datap.next {
   363  		if len(datap.pclntable) == 0 {
   364  			continue
   365  		}
   366  		base := uintptr(unsafe.Pointer(&datap.pclntable[0]))
   367  		if base <= ptr && ptr < base+uintptr(len(datap.pclntable)) {
   368  			mod = datap
   369  			break
   370  		}
   371  	}
   372  	return funcInfo{f, mod}
   373  }
   374  
   375  // pcHeader holds data used by the pclntab lookups.
   376  type pcHeader struct {
   377  	magic          uint32  // 0xFFFFFFF1
   378  	pad1, pad2     uint8   // 0,0
   379  	minLC          uint8   // min instruction size
   380  	ptrSize        uint8   // size of a ptr in bytes
   381  	nfunc          int     // number of functions in the module
   382  	nfiles         uint    // number of entries in the file tab
   383  	textStart      uintptr // base for function entry PC offsets in this module, equal to moduledata.text
   384  	funcnameOffset uintptr // offset to the funcnametab variable from pcHeader
   385  	cuOffset       uintptr // offset to the cutab variable from pcHeader
   386  	filetabOffset  uintptr // offset to the filetab variable from pcHeader
   387  	pctabOffset    uintptr // offset to the pctab variable from pcHeader
   388  	pclnOffset     uintptr // offset to the pclntab variable from pcHeader
   389  }
   390  
   391  // moduledata records information about the layout of the executable
   392  // image. It is written by the linker. Any changes here must be
   393  // matched changes to the code in cmd/link/internal/ld/symtab.go:symtab.
   394  // moduledata is stored in statically allocated non-pointer memory;
   395  // none of the pointers here are visible to the garbage collector.
   396  type moduledata struct {
   397  	sys.NotInHeap // Only in static data
   398  
   399  	pcHeader     *pcHeader
   400  	funcnametab  []byte
   401  	cutab        []uint32
   402  	filetab      []byte
   403  	pctab        []byte
   404  	pclntable    []byte
   405  	ftab         []functab
   406  	findfunctab  uintptr
   407  	minpc, maxpc uintptr
   408  
   409  	text, etext           uintptr
   410  	noptrdata, enoptrdata uintptr
   411  	data, edata           uintptr
   412  	bss, ebss             uintptr
   413  	noptrbss, enoptrbss   uintptr
   414  	covctrs, ecovctrs     uintptr
   415  	end, gcdata, gcbss    uintptr
   416  	types, etypes         uintptr
   417  	rodata                uintptr
   418  	gofunc                uintptr // go.func.*
   419  
   420  	textsectmap []textsect
   421  	typelinks   []int32 // offsets from types
   422  	itablinks   []*itab
   423  
   424  	ptab []ptabEntry
   425  
   426  	pluginpath string
   427  	pkghashes  []modulehash
   428  
   429  	// This slice records the initializing tasks that need to be
   430  	// done to start up the program. It is built by the linker.
   431  	inittasks []*initTask
   432  
   433  	modulename   string
   434  	modulehashes []modulehash
   435  
   436  	hasmain uint8 // 1 if module contains the main function, 0 otherwise
   437  	bad     bool  // module failed to load and should be ignored
   438  
   439  	gcdatamask, gcbssmask bitvector
   440  
   441  	typemap map[typeOff]*_type // offset to *_rtype in previous module
   442  
   443  	next *moduledata
   444  }
   445  
   446  // A modulehash is used to compare the ABI of a new module or a
   447  // package in a new module with the loaded program.
   448  //
   449  // For each shared library a module links against, the linker creates an entry in the
   450  // moduledata.modulehashes slice containing the name of the module, the abi hash seen
   451  // at link time and a pointer to the runtime abi hash. These are checked in
   452  // moduledataverify1 below.
   453  //
   454  // For each loaded plugin, the pkghashes slice has a modulehash of the
   455  // newly loaded package that can be used to check the plugin's version of
   456  // a package against any previously loaded version of the package.
   457  // This is done in plugin.lastmoduleinit.
   458  type modulehash struct {
   459  	modulename   string
   460  	linktimehash string
   461  	runtimehash  *string
   462  }
   463  
   464  // pinnedTypemaps are the map[typeOff]*_type from the moduledata objects.
   465  //
   466  // These typemap objects are allocated at run time on the heap, but the
   467  // only direct reference to them is in the moduledata, created by the
   468  // linker and marked SNOPTRDATA so it is ignored by the GC.
   469  //
   470  // To make sure the map isn't collected, we keep a second reference here.
   471  var pinnedTypemaps []map[typeOff]*_type
   472  
   473  // aixStaticDataBase (used only on AIX) holds the unrelocated address
   474  // of the data section, set by the linker.
   475  //
   476  // On AIX, an R_ADDR relocation from an RODATA symbol to a DATA symbol
   477  // does not work, as the dynamic loader can change the address of the
   478  // data section, and it is not possible to apply a dynamic relocation
   479  // to RODATA. In order to get the correct address, we need to apply
   480  // the delta between unrelocated and relocated data section addresses.
   481  // aixStaticDataBase is the unrelocated address, and moduledata.data is
   482  // the relocated one.
   483  var aixStaticDataBase uintptr // linker symbol
   484  
   485  var firstmoduledata moduledata // linker symbol
   486  
   487  // lastmoduledatap should be an internal detail,
   488  // but widely used packages access it using linkname.
   489  // Notable members of the hall of shame include:
   490  //   - github.com/bytedance/sonic
   491  //
   492  // Do not remove or change the type signature.
   493  // See go.dev/issues/67401.
   494  // See go.dev/issues/71672.
   495  //
   496  //go:linkname lastmoduledatap
   497  var lastmoduledatap *moduledata // linker symbol
   498  
   499  var modulesSlice *[]*moduledata // see activeModules
   500  
   501  // activeModules returns a slice of active modules.
   502  //
   503  // A module is active once its gcdatamask and gcbssmask have been
   504  // assembled and it is usable by the GC.
   505  //
   506  // This is nosplit/nowritebarrier because it is called by the
   507  // cgo pointer checking code.
   508  //
   509  //go:nosplit
   510  //go:nowritebarrier
   511  func activeModules() []*moduledata {
   512  	p := (*[]*moduledata)(atomic.Loadp(unsafe.Pointer(&modulesSlice)))
   513  	if p == nil {
   514  		return nil
   515  	}
   516  	return *p
   517  }
   518  
   519  // modulesinit creates the active modules slice out of all loaded modules.
   520  //
   521  // When a module is first loaded by the dynamic linker, an .init_array
   522  // function (written by cmd/link) is invoked to call addmoduledata,
   523  // appending to the module to the linked list that starts with
   524  // firstmoduledata.
   525  //
   526  // There are two times this can happen in the lifecycle of a Go
   527  // program. First, if compiled with -linkshared, a number of modules
   528  // built with -buildmode=shared can be loaded at program initialization.
   529  // Second, a Go program can load a module while running that was built
   530  // with -buildmode=plugin.
   531  //
   532  // After loading, this function is called which initializes the
   533  // moduledata so it is usable by the GC and creates a new activeModules
   534  // list.
   535  //
   536  // Only one goroutine may call modulesinit at a time.
   537  func modulesinit() {
   538  	modules := new([]*moduledata)
   539  	for md := &firstmoduledata; md != nil; md = md.next {
   540  		if md.bad {
   541  			continue
   542  		}
   543  		*modules = append(*modules, md)
   544  		if md.gcdatamask == (bitvector{}) {
   545  			scanDataSize := md.edata - md.data
   546  			md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), scanDataSize)
   547  			scanBSSSize := md.ebss - md.bss
   548  			md.gcbssmask = progToPointerMask((*byte)(unsafe.Pointer(md.gcbss)), scanBSSSize)
   549  			gcController.addGlobals(int64(scanDataSize + scanBSSSize))
   550  		}
   551  	}
   552  
   553  	// Modules appear in the moduledata linked list in the order they are
   554  	// loaded by the dynamic loader, with one exception: the
   555  	// firstmoduledata itself the module that contains the runtime. This
   556  	// is not always the first module (when using -buildmode=shared, it
   557  	// is typically libstd.so, the second module). The order matters for
   558  	// typelinksinit, so we swap the first module with whatever module
   559  	// contains the main function.
   560  	//
   561  	// See Issue #18729.
   562  	for i, md := range *modules {
   563  		if md.hasmain != 0 {
   564  			(*modules)[0] = md
   565  			(*modules)[i] = &firstmoduledata
   566  			break
   567  		}
   568  	}
   569  
   570  	atomicstorep(unsafe.Pointer(&modulesSlice), unsafe.Pointer(modules))
   571  }
   572  
   573  type functab struct {
   574  	entryoff uint32 // relative to runtime.text
   575  	funcoff  uint32
   576  }
   577  
   578  // Mapping information for secondary text sections
   579  
   580  type textsect struct {
   581  	vaddr    uintptr // prelinked section vaddr
   582  	end      uintptr // vaddr + section length
   583  	baseaddr uintptr // relocated section address
   584  }
   585  
   586  // findfuncbucket is an array of these structures.
   587  // Each bucket represents 4096 bytes of the text segment.
   588  // Each subbucket represents 256 bytes of the text segment.
   589  // To find a function given a pc, locate the bucket and subbucket for
   590  // that pc. Add together the idx and subbucket value to obtain a
   591  // function index. Then scan the functab array starting at that
   592  // index to find the target function.
   593  // This table uses 20 bytes for every 4096 bytes of code, or ~0.5% overhead.
   594  type findfuncbucket struct {
   595  	idx        uint32
   596  	subbuckets [16]byte
   597  }
   598  
   599  func moduledataverify() {
   600  	for datap := &firstmoduledata; datap != nil; datap = datap.next {
   601  		moduledataverify1(datap)
   602  	}
   603  }
   604  
   605  const debugPcln = false
   606  
   607  // moduledataverify1 should be an internal detail,
   608  // but widely used packages access it using linkname.
   609  // Notable members of the hall of shame include:
   610  //   - github.com/bytedance/sonic
   611  //
   612  // Do not remove or change the type signature.
   613  // See go.dev/issues/67401.
   614  // See go.dev/issues/71672.
   615  //
   616  //go:linkname moduledataverify1
   617  func moduledataverify1(datap *moduledata) {
   618  	// Check that the pclntab's format is valid.
   619  	hdr := datap.pcHeader
   620  	if hdr.magic != 0xfffffff1 || hdr.pad1 != 0 || hdr.pad2 != 0 ||
   621  		hdr.minLC != sys.PCQuantum || hdr.ptrSize != goarch.PtrSize || hdr.textStart != datap.text {
   622  		println("runtime: pcHeader: magic=", hex(hdr.magic), "pad1=", hdr.pad1, "pad2=", hdr.pad2,
   623  			"minLC=", hdr.minLC, "ptrSize=", hdr.ptrSize, "pcHeader.textStart=", hex(hdr.textStart),
   624  			"text=", hex(datap.text), "pluginpath=", datap.pluginpath)
   625  		throw("invalid function symbol table")
   626  	}
   627  
   628  	// ftab is lookup table for function by program counter.
   629  	nftab := len(datap.ftab) - 1
   630  	for i := 0; i < nftab; i++ {
   631  		// NOTE: ftab[nftab].entry is legal; it is the address beyond the final function.
   632  		if datap.ftab[i].entryoff > datap.ftab[i+1].entryoff {
   633  			f1 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i].funcoff])), datap}
   634  			f2 := funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[i+1].funcoff])), datap}
   635  			f2name := "end"
   636  			if i+1 < nftab {
   637  				f2name = funcname(f2)
   638  			}
   639  			println("function symbol table not sorted by PC offset:", hex(datap.ftab[i].entryoff), funcname(f1), ">", hex(datap.ftab[i+1].entryoff), f2name, ", plugin:", datap.pluginpath)
   640  			for j := 0; j <= i; j++ {
   641  				println("\t", hex(datap.ftab[j].entryoff), funcname(funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[datap.ftab[j].funcoff])), datap}))
   642  			}
   643  			if GOOS == "aix" && isarchive {
   644  				println("-Wl,-bnoobjreorder is mandatory on aix/ppc64 with c-archive")
   645  			}
   646  			throw("invalid runtime symbol table")
   647  		}
   648  	}
   649  
   650  	min := datap.textAddr(datap.ftab[0].entryoff)
   651  	max := datap.textAddr(datap.ftab[nftab].entryoff)
   652  	minpc := datap.minpc
   653  	maxpc := datap.maxpc
   654  	if GOARCH == "wasm" {
   655  		// On Wasm, the func table contains the function index, whereas
   656  		// the "PC" is function index << 16 + block index.
   657  		maxpc = alignUp(maxpc, 1<<16) // round up for end PC
   658  	}
   659  	if minpc != min || maxpc != max {
   660  		println("minpc=", hex(minpc), "min=", hex(min), "maxpc=", hex(maxpc), "max=", hex(max))
   661  		throw("minpc or maxpc invalid")
   662  	}
   663  
   664  	for _, modulehash := range datap.modulehashes {
   665  		if modulehash.linktimehash != *modulehash.runtimehash {
   666  			println("abi mismatch detected between", datap.modulename, "and", modulehash.modulename)
   667  			throw("abi mismatch")
   668  		}
   669  	}
   670  }
   671  
   672  // textAddr returns md.text + off, with special handling for multiple text sections.
   673  // off is a (virtual) offset computed at internal linking time,
   674  // before the external linker adjusts the sections' base addresses.
   675  //
   676  // The text, or instruction stream is generated as one large buffer.
   677  // The off (offset) for a function is its offset within this buffer.
   678  // If the total text size gets too large, there can be issues on platforms like ppc64
   679  // if the target of calls are too far for the call instruction.
   680  // To resolve the large text issue, the text is split into multiple text sections
   681  // to allow the linker to generate long calls when necessary.
   682  // When this happens, the vaddr for each text section is set to its offset within the text.
   683  // Each function's offset is compared against the section vaddrs and ends to determine the containing section.
   684  // Then the section relative offset is added to the section's
   685  // relocated baseaddr to compute the function address.
   686  //
   687  // It is nosplit because it is part of the findfunc implementation.
   688  //
   689  //go:nosplit
   690  func (md *moduledata) textAddr(off32 uint32) uintptr {
   691  	off := uintptr(off32)
   692  	res := md.text + off
   693  	if len(md.textsectmap) > 1 {
   694  		for i, sect := range md.textsectmap {
   695  			// For the last section, include the end address (etext), as it is included in the functab.
   696  			if off >= sect.vaddr && off < sect.end || (i == len(md.textsectmap)-1 && off == sect.end) {
   697  				res = sect.baseaddr + off - sect.vaddr
   698  				break
   699  			}
   700  		}
   701  		if res > md.etext && GOARCH != "wasm" { // on wasm, functions do not live in the same address space as the linear memory
   702  			println("runtime: textAddr", hex(res), "out of range", hex(md.text), "-", hex(md.etext))
   703  			throw("runtime: text offset out of range")
   704  		}
   705  	}
   706  	if GOARCH == "wasm" {
   707  		// On Wasm, a text offset (e.g. in the method table) is function index, whereas
   708  		// the "PC" is function index << 16 + block index.
   709  		res <<= 16
   710  	}
   711  	return res
   712  }
   713  
   714  // textOff is the opposite of textAddr. It converts a PC to a (virtual) offset
   715  // to md.text, and returns if the PC is in any Go text section.
   716  //
   717  // It is nosplit because it is part of the findfunc implementation.
   718  //
   719  //go:nosplit
   720  func (md *moduledata) textOff(pc uintptr) (uint32, bool) {
   721  	off := pc - md.text
   722  	if GOARCH == "wasm" {
   723  		// On Wasm, the func table contains the function index, whereas
   724  		// the "PC" is function index << 16 + block index.
   725  		off >>= 16
   726  	}
   727  	res := uint32(off)
   728  	if len(md.textsectmap) > 1 {
   729  		if GOARCH == "wasm" {
   730  			fatal("unexpected multiple text sections on Wasm")
   731  		}
   732  		for i, sect := range md.textsectmap {
   733  			if sect.baseaddr > pc {
   734  				// pc is not in any section.
   735  				return 0, false
   736  			}
   737  			end := sect.baseaddr + (sect.end - sect.vaddr)
   738  			// For the last section, include the end address (etext), as it is included in the functab.
   739  			if i == len(md.textsectmap)-1 {
   740  				end++
   741  			}
   742  			if pc < end {
   743  				res = uint32(pc - sect.baseaddr + sect.vaddr)
   744  				break
   745  			}
   746  		}
   747  	}
   748  	return res, true
   749  }
   750  
   751  // funcName returns the string at nameOff in the function name table.
   752  func (md *moduledata) funcName(nameOff int32) string {
   753  	if nameOff == 0 {
   754  		return ""
   755  	}
   756  	return gostringnocopy(&md.funcnametab[nameOff])
   757  }
   758  
   759  // Despite being an exported symbol,
   760  // FuncForPC is linknamed by widely used packages.
   761  // Notable members of the hall of shame include:
   762  //   - gitee.com/quant1x/gox
   763  //
   764  // Do not remove or change the type signature.
   765  // See go.dev/issue/67401.
   766  //
   767  // Note that this comment is not part of the doc comment.
   768  //
   769  //go:linkname FuncForPC
   770  
   771  // FuncForPC returns a *[Func] describing the function that contains the
   772  // given program counter address, or else nil.
   773  //
   774  // If pc represents multiple functions because of inlining, it returns
   775  // the *Func describing the innermost function, but with an entry of
   776  // the outermost function.
   777  func FuncForPC(pc uintptr) *Func {
   778  	f := findfunc(pc)
   779  	if !f.valid() {
   780  		return nil
   781  	}
   782  	// This must interpret PC non-strictly so bad PCs (those between functions) don't crash the runtime.
   783  	// We just report the preceding function in that situation. See issue 29735.
   784  	// TODO: Perhaps we should report no function at all in that case.
   785  	// The runtime currently doesn't have function end info, alas.
   786  	u, uf := newInlineUnwinder(f, pc)
   787  	if !u.isInlined(uf) {
   788  		return f._Func()
   789  	}
   790  	sf := u.srcFunc(uf)
   791  	file, line := u.fileLine(uf)
   792  	fi := &funcinl{
   793  		ones:      ^uint32(0),
   794  		entry:     f.entry(), // entry of the real (the outermost) function.
   795  		name:      sf.name(),
   796  		file:      file,
   797  		line:      int32(line),
   798  		startLine: sf.startLine,
   799  	}
   800  	return (*Func)(unsafe.Pointer(fi))
   801  }
   802  
   803  // Name returns the name of the function.
   804  func (f *Func) Name() string {
   805  	if f == nil {
   806  		return ""
   807  	}
   808  	fn := f.raw()
   809  	if fn.isInlined() { // inlined version
   810  		fi := (*funcinl)(unsafe.Pointer(fn))
   811  		return funcNameForPrint(fi.name)
   812  	}
   813  	return funcNameForPrint(funcname(f.funcInfo()))
   814  }
   815  
   816  // Entry returns the entry address of the function.
   817  func (f *Func) Entry() uintptr {
   818  	fn := f.raw()
   819  	if fn.isInlined() { // inlined version
   820  		fi := (*funcinl)(unsafe.Pointer(fn))
   821  		return fi.entry
   822  	}
   823  	return fn.funcInfo().entry()
   824  }
   825  
   826  // FileLine returns the file name and line number of the
   827  // source code corresponding to the program counter pc.
   828  // The result will not be accurate if pc is not a program
   829  // counter within f.
   830  func (f *Func) FileLine(pc uintptr) (file string, line int) {
   831  	fn := f.raw()
   832  	if fn.isInlined() { // inlined version
   833  		fi := (*funcinl)(unsafe.Pointer(fn))
   834  		return fi.file, int(fi.line)
   835  	}
   836  	// Pass strict=false here, because anyone can call this function,
   837  	// and they might just be wrong about targetpc belonging to f.
   838  	file, line32 := funcline1(f.funcInfo(), pc, false)
   839  	return file, int(line32)
   840  }
   841  
   842  // startLine returns the starting line number of the function. i.e., the line
   843  // number of the func keyword.
   844  func (f *Func) startLine() int32 {
   845  	fn := f.raw()
   846  	if fn.isInlined() { // inlined version
   847  		fi := (*funcinl)(unsafe.Pointer(fn))
   848  		return fi.startLine
   849  	}
   850  	return fn.funcInfo().startLine
   851  }
   852  
   853  // findmoduledatap looks up the moduledata for a PC.
   854  //
   855  // It is nosplit because it's part of the isgoexception
   856  // implementation.
   857  //
   858  //go:nosplit
   859  func findmoduledatap(pc uintptr) *moduledata {
   860  	for datap := &firstmoduledata; datap != nil; datap = datap.next {
   861  		if datap.minpc <= pc && pc < datap.maxpc {
   862  			return datap
   863  		}
   864  	}
   865  	return nil
   866  }
   867  
   868  type funcInfo struct {
   869  	*_func
   870  	datap *moduledata
   871  }
   872  
   873  func (f funcInfo) valid() bool {
   874  	return f._func != nil
   875  }
   876  
   877  func (f funcInfo) _Func() *Func {
   878  	return (*Func)(unsafe.Pointer(f._func))
   879  }
   880  
   881  // isInlined reports whether f should be re-interpreted as a *funcinl.
   882  func (f *_func) isInlined() bool {
   883  	return f.entryOff == ^uint32(0) // see comment for funcinl.ones
   884  }
   885  
   886  // entry returns the entry PC for f.
   887  //
   888  // entry should be an internal detail,
   889  // but widely used packages access it using linkname.
   890  // Notable members of the hall of shame include:
   891  //   - github.com/phuslu/log
   892  //
   893  // Do not remove or change the type signature.
   894  // See go.dev/issue/67401.
   895  func (f funcInfo) entry() uintptr {
   896  	return f.datap.textAddr(f.entryOff)
   897  }
   898  
   899  //go:linkname badFuncInfoEntry runtime.funcInfo.entry
   900  func badFuncInfoEntry(funcInfo) uintptr
   901  
   902  // findfunc looks up function metadata for a PC.
   903  //
   904  // It is nosplit because it's part of the isgoexception
   905  // implementation.
   906  //
   907  // findfunc should be an internal detail,
   908  // but widely used packages access it using linkname.
   909  // Notable members of the hall of shame include:
   910  //   - github.com/phuslu/log
   911  //
   912  // Do not remove or change the type signature.
   913  // See go.dev/issue/67401.
   914  //
   915  //go:nosplit
   916  //go:linkname findfunc
   917  func findfunc(pc uintptr) funcInfo {
   918  	datap := findmoduledatap(pc)
   919  	if datap == nil {
   920  		return funcInfo{}
   921  	}
   922  	const nsub = uintptr(len(findfuncbucket{}.subbuckets))
   923  
   924  	pcOff, ok := datap.textOff(pc)
   925  	if !ok {
   926  		return funcInfo{}
   927  	}
   928  
   929  	x := uintptr(pcOff) + datap.text - datap.minpc // TODO: are datap.text and datap.minpc always equal?
   930  	if GOARCH == "wasm" {
   931  		// On Wasm, pcOff is the function index, whereas
   932  		// the "PC" is function index << 16 + block index.
   933  		x = uintptr(pcOff)<<16 + datap.text - datap.minpc
   934  	}
   935  	b := x / abi.FuncTabBucketSize
   936  	i := x % abi.FuncTabBucketSize / (abi.FuncTabBucketSize / nsub)
   937  
   938  	ffb := (*findfuncbucket)(add(unsafe.Pointer(datap.findfunctab), b*unsafe.Sizeof(findfuncbucket{})))
   939  	idx := ffb.idx + uint32(ffb.subbuckets[i])
   940  
   941  	// Find the ftab entry.
   942  	for datap.ftab[idx+1].entryoff <= pcOff {
   943  		idx++
   944  	}
   945  
   946  	funcoff := datap.ftab[idx].funcoff
   947  	return funcInfo{(*_func)(unsafe.Pointer(&datap.pclntable[funcoff])), datap}
   948  }
   949  
   950  // A srcFunc represents a logical function in the source code. This may
   951  // correspond to an actual symbol in the binary text, or it may correspond to a
   952  // source function that has been inlined.
   953  type srcFunc struct {
   954  	datap     *moduledata
   955  	nameOff   int32
   956  	startLine int32
   957  	funcID    abi.FuncID
   958  }
   959  
   960  func (f funcInfo) srcFunc() srcFunc {
   961  	if !f.valid() {
   962  		return srcFunc{}
   963  	}
   964  	return srcFunc{f.datap, f.nameOff, f.startLine, f.funcID}
   965  }
   966  
   967  // name should be an internal detail,
   968  // but widely used packages access it using linkname.
   969  // Notable members of the hall of shame include:
   970  //   - github.com/phuslu/log
   971  //
   972  // Do not remove or change the type signature.
   973  // See go.dev/issue/67401.
   974  func (s srcFunc) name() string {
   975  	if s.datap == nil {
   976  		return ""
   977  	}
   978  	return s.datap.funcName(s.nameOff)
   979  }
   980  
   981  //go:linkname badSrcFuncName runtime.srcFunc.name
   982  func badSrcFuncName(srcFunc) string
   983  
   984  type pcvalueCache struct {
   985  	entries [2][8]pcvalueCacheEnt
   986  	inUse   int
   987  }
   988  
   989  type pcvalueCacheEnt struct {
   990  	// targetpc and off together are the key of this cache entry.
   991  	targetpc uintptr
   992  	off      uint32
   993  
   994  	val   int32   // The value of this entry.
   995  	valPC uintptr // The PC at which val starts
   996  }
   997  
   998  // pcvalueCacheKey returns the outermost index in a pcvalueCache to use for targetpc.
   999  // It must be very cheap to calculate.
  1000  // For now, align to goarch.PtrSize and reduce mod the number of entries.
  1001  // In practice, this appears to be fairly randomly and evenly distributed.
  1002  func pcvalueCacheKey(targetpc uintptr) uintptr {
  1003  	return (targetpc / goarch.PtrSize) % uintptr(len(pcvalueCache{}.entries))
  1004  }
  1005  
  1006  // Returns the PCData value, and the PC where this value starts.
  1007  func pcvalue(f funcInfo, off uint32, targetpc uintptr, strict bool) (int32, uintptr) {
  1008  	// If true, when we get a cache hit, still look up the data and make sure it
  1009  	// matches the cached contents.
  1010  	const debugCheckCache = false
  1011  
  1012  	// If true, skip checking the cache entirely.
  1013  	const skipCache = false
  1014  
  1015  	if off == 0 {
  1016  		return -1, 0
  1017  	}
  1018  
  1019  	// Check the cache. This speeds up walks of deep stacks, which
  1020  	// tend to have the same recursive functions over and over,
  1021  	// or repetitive stacks between goroutines.
  1022  	var checkVal int32
  1023  	var checkPC uintptr
  1024  	ck := pcvalueCacheKey(targetpc)
  1025  	if !skipCache {
  1026  		mp := acquirem()
  1027  		cache := &mp.pcvalueCache
  1028  		// The cache can be used by the signal handler on this M. Avoid
  1029  		// re-entrant use of the cache. The signal handler can also write inUse,
  1030  		// but will always restore its value, so we can use a regular increment
  1031  		// even if we get signaled in the middle of it.
  1032  		cache.inUse++
  1033  		if cache.inUse == 1 {
  1034  			for i := range cache.entries[ck] {
  1035  				// We check off first because we're more
  1036  				// likely to have multiple entries with
  1037  				// different offsets for the same targetpc
  1038  				// than the other way around, so we'll usually
  1039  				// fail in the first clause.
  1040  				ent := &cache.entries[ck][i]
  1041  				if ent.off == off && ent.targetpc == targetpc {
  1042  					val, pc := ent.val, ent.valPC
  1043  					if debugCheckCache {
  1044  						checkVal, checkPC = ent.val, ent.valPC
  1045  						break
  1046  					} else {
  1047  						cache.inUse--
  1048  						releasem(mp)
  1049  						return val, pc
  1050  					}
  1051  				}
  1052  			}
  1053  		} else if debugCheckCache && (cache.inUse < 1 || cache.inUse > 2) {
  1054  			// Catch accounting errors or deeply reentrant use. In principle
  1055  			// "inUse" should never exceed 2.
  1056  			throw("cache.inUse out of range")
  1057  		}
  1058  		cache.inUse--
  1059  		releasem(mp)
  1060  	}
  1061  
  1062  	if !f.valid() {
  1063  		if strict && panicking.Load() == 0 {
  1064  			println("runtime: no module data for", hex(f.entry()))
  1065  			throw("no module data")
  1066  		}
  1067  		return -1, 0
  1068  	}
  1069  	datap := f.datap
  1070  	p := datap.pctab[off:]
  1071  	pc := f.entry()
  1072  	prevpc := pc
  1073  	val := int32(-1)
  1074  	for {
  1075  		var ok bool
  1076  		p, ok = step(p, &pc, &val, pc == f.entry())
  1077  		if !ok {
  1078  			break
  1079  		}
  1080  		if targetpc < pc {
  1081  			// Replace a random entry in the cache. Random
  1082  			// replacement prevents a performance cliff if
  1083  			// a recursive stack's cycle is slightly
  1084  			// larger than the cache.
  1085  			// Put the new element at the beginning,
  1086  			// since it is the most likely to be newly used.
  1087  			if debugCheckCache && checkPC != 0 {
  1088  				if checkVal != val || checkPC != prevpc {
  1089  					print("runtime: table value ", val, "@", prevpc, " != cache value ", checkVal, "@", checkPC, " at PC ", targetpc, " off ", off, "\n")
  1090  					throw("bad pcvalue cache")
  1091  				}
  1092  			} else {
  1093  				mp := acquirem()
  1094  				cache := &mp.pcvalueCache
  1095  				cache.inUse++
  1096  				if cache.inUse == 1 {
  1097  					e := &cache.entries[ck]
  1098  					ci := cheaprandn(uint32(len(cache.entries[ck])))
  1099  					e[ci] = e[0]
  1100  					e[0] = pcvalueCacheEnt{
  1101  						targetpc: targetpc,
  1102  						off:      off,
  1103  						val:      val,
  1104  						valPC:    prevpc,
  1105  					}
  1106  				}
  1107  				cache.inUse--
  1108  				releasem(mp)
  1109  			}
  1110  
  1111  			return val, prevpc
  1112  		}
  1113  		prevpc = pc
  1114  	}
  1115  
  1116  	// If there was a table, it should have covered all program counters.
  1117  	// If not, something is wrong.
  1118  	if panicking.Load() != 0 || !strict {
  1119  		return -1, 0
  1120  	}
  1121  
  1122  	print("runtime: invalid pc-encoded table f=", funcname(f), " pc=", hex(pc), " targetpc=", hex(targetpc), " tab=", p, "\n")
  1123  
  1124  	p = datap.pctab[off:]
  1125  	pc = f.entry()
  1126  	val = -1
  1127  	for {
  1128  		var ok bool
  1129  		p, ok = step(p, &pc, &val, pc == f.entry())
  1130  		if !ok {
  1131  			break
  1132  		}
  1133  		print("\tvalue=", val, " until pc=", hex(pc), "\n")
  1134  	}
  1135  
  1136  	throw("invalid runtime symbol table")
  1137  	return -1, 0
  1138  }
  1139  
  1140  func funcname(f funcInfo) string {
  1141  	if !f.valid() {
  1142  		return ""
  1143  	}
  1144  	return f.datap.funcName(f.nameOff)
  1145  }
  1146  
  1147  func funcpkgpath(f funcInfo) string {
  1148  	name := funcNameForPrint(funcname(f))
  1149  	i := len(name) - 1
  1150  	for ; i > 0; i-- {
  1151  		if name[i] == '/' {
  1152  			break
  1153  		}
  1154  	}
  1155  	for ; i < len(name); i++ {
  1156  		if name[i] == '.' {
  1157  			break
  1158  		}
  1159  	}
  1160  	return name[:i]
  1161  }
  1162  
  1163  func funcfile(f funcInfo, fileno int32) string {
  1164  	datap := f.datap
  1165  	if !f.valid() {
  1166  		return "?"
  1167  	}
  1168  	// Make sure the cu index and file offset are valid
  1169  	if fileoff := datap.cutab[f.cuOffset+uint32(fileno)]; fileoff != ^uint32(0) {
  1170  		return gostringnocopy(&datap.filetab[fileoff])
  1171  	}
  1172  	// pcln section is corrupt.
  1173  	return "?"
  1174  }
  1175  
  1176  // funcline1 should be an internal detail,
  1177  // but widely used packages access it using linkname.
  1178  // Notable members of the hall of shame include:
  1179  //   - github.com/phuslu/log
  1180  //
  1181  // Do not remove or change the type signature.
  1182  // See go.dev/issue/67401.
  1183  //
  1184  //go:linkname funcline1
  1185  func funcline1(f funcInfo, targetpc uintptr, strict bool) (file string, line int32) {
  1186  	datap := f.datap
  1187  	if !f.valid() {
  1188  		return "?", 0
  1189  	}
  1190  	fileno, _ := pcvalue(f, f.pcfile, targetpc, strict)
  1191  	line, _ = pcvalue(f, f.pcln, targetpc, strict)
  1192  	if fileno == -1 || line == -1 || int(fileno) >= len(datap.filetab) {
  1193  		// print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n")
  1194  		return "?", 0
  1195  	}
  1196  	file = funcfile(f, fileno)
  1197  	return
  1198  }
  1199  
  1200  func funcline(f funcInfo, targetpc uintptr) (file string, line int32) {
  1201  	return funcline1(f, targetpc, true)
  1202  }
  1203  
  1204  func funcspdelta(f funcInfo, targetpc uintptr) int32 {
  1205  	x, _ := pcvalue(f, f.pcsp, targetpc, true)
  1206  	if debugPcln && x&(goarch.PtrSize-1) != 0 {
  1207  		print("invalid spdelta ", funcname(f), " ", hex(f.entry()), " ", hex(targetpc), " ", hex(f.pcsp), " ", x, "\n")
  1208  		throw("bad spdelta")
  1209  	}
  1210  	return x
  1211  }
  1212  
  1213  // funcMaxSPDelta returns the maximum spdelta at any point in f.
  1214  func funcMaxSPDelta(f funcInfo) int32 {
  1215  	datap := f.datap
  1216  	p := datap.pctab[f.pcsp:]
  1217  	pc := f.entry()
  1218  	val := int32(-1)
  1219  	most := int32(0)
  1220  	for {
  1221  		var ok bool
  1222  		p, ok = step(p, &pc, &val, pc == f.entry())
  1223  		if !ok {
  1224  			return most
  1225  		}
  1226  		most = max(most, val)
  1227  	}
  1228  }
  1229  
  1230  func pcdatastart(f funcInfo, table uint32) uint32 {
  1231  	return *(*uint32)(add(unsafe.Pointer(&f.nfuncdata), unsafe.Sizeof(f.nfuncdata)+uintptr(table)*4))
  1232  }
  1233  
  1234  func pcdatavalue(f funcInfo, table uint32, targetpc uintptr) int32 {
  1235  	if table >= f.npcdata {
  1236  		return -1
  1237  	}
  1238  	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, true)
  1239  	return r
  1240  }
  1241  
  1242  func pcdatavalue1(f funcInfo, table uint32, targetpc uintptr, strict bool) int32 {
  1243  	if table >= f.npcdata {
  1244  		return -1
  1245  	}
  1246  	r, _ := pcvalue(f, pcdatastart(f, table), targetpc, strict)
  1247  	return r
  1248  }
  1249  
  1250  // Like pcdatavalue, but also return the start PC of this PCData value.
  1251  func pcdatavalue2(f funcInfo, table uint32, targetpc uintptr) (int32, uintptr) {
  1252  	if table >= f.npcdata {
  1253  		return -1, 0
  1254  	}
  1255  	return pcvalue(f, pcdatastart(f, table), targetpc, true)
  1256  }
  1257  
  1258  // funcdata returns a pointer to the ith funcdata for f.
  1259  // funcdata should be kept in sync with cmd/link:writeFuncs.
  1260  func funcdata(f funcInfo, i uint8) unsafe.Pointer {
  1261  	if i < 0 || i >= f.nfuncdata {
  1262  		return nil
  1263  	}
  1264  	base := f.datap.gofunc // load gofunc address early so that we calculate during cache misses
  1265  	p := uintptr(unsafe.Pointer(&f.nfuncdata)) + unsafe.Sizeof(f.nfuncdata) + uintptr(f.npcdata)*4 + uintptr(i)*4
  1266  	off := *(*uint32)(unsafe.Pointer(p))
  1267  	// Return off == ^uint32(0) ? 0 : f.datap.gofunc + uintptr(off), but without branches.
  1268  	// The compiler calculates mask on most architectures using conditional assignment.
  1269  	var mask uintptr
  1270  	if off == ^uint32(0) {
  1271  		mask = 1
  1272  	}
  1273  	mask--
  1274  	raw := base + uintptr(off)
  1275  	return unsafe.Pointer(raw & mask)
  1276  }
  1277  
  1278  // step advances to the next pc, value pair in the encoded table.
  1279  func step(p []byte, pc *uintptr, val *int32, first bool) (newp []byte, ok bool) {
  1280  	// For both uvdelta and pcdelta, the common case (~70%)
  1281  	// is that they are a single byte. If so, avoid calling readvarint.
  1282  	uvdelta := uint32(p[0])
  1283  	if uvdelta == 0 && !first {
  1284  		return nil, false
  1285  	}
  1286  	n := uint32(1)
  1287  	if uvdelta&0x80 != 0 {
  1288  		n, uvdelta = readvarint(p)
  1289  	}
  1290  	*val += int32(-(uvdelta & 1) ^ (uvdelta >> 1))
  1291  	p = p[n:]
  1292  
  1293  	pcdelta := uint32(p[0])
  1294  	n = 1
  1295  	if pcdelta&0x80 != 0 {
  1296  		n, pcdelta = readvarint(p)
  1297  	}
  1298  	p = p[n:]
  1299  	*pc += uintptr(pcdelta * sys.PCQuantum)
  1300  	return p, true
  1301  }
  1302  
  1303  // readvarint reads a varint from p.
  1304  func readvarint(p []byte) (read uint32, val uint32) {
  1305  	var v, shift, n uint32
  1306  	for {
  1307  		b := p[n]
  1308  		n++
  1309  		v |= uint32(b&0x7F) << (shift & 31)
  1310  		if b&0x80 == 0 {
  1311  			break
  1312  		}
  1313  		shift += 7
  1314  	}
  1315  	return n, v
  1316  }
  1317  
  1318  type stackmap struct {
  1319  	n        int32   // number of bitmaps
  1320  	nbit     int32   // number of bits in each bitmap
  1321  	bytedata [1]byte // bitmaps, each starting on a byte boundary
  1322  }
  1323  
  1324  //go:nowritebarrier
  1325  func stackmapdata(stkmap *stackmap, n int32) bitvector {
  1326  	// Check this invariant only when stackDebug is on at all.
  1327  	// The invariant is already checked by many of stackmapdata's callers,
  1328  	// and disabling it by default allows stackmapdata to be inlined.
  1329  	if stackDebug > 0 && (n < 0 || n >= stkmap.n) {
  1330  		throw("stackmapdata: index out of range")
  1331  	}
  1332  	return bitvector{stkmap.nbit, addb(&stkmap.bytedata[0], uintptr(n*((stkmap.nbit+7)>>3)))}
  1333  }
  1334  

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