symtab.go

     1  // Copyright 2023 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 abi
     6  
     7  // PCLnTabMagic is the version at the start of the PC/line table.
     8  // This is the start of the .pclntab section, and is also runtime.pcHeader.
     9  // The magic numbers are chosen such that reading the value with
    10  // a different endianness does not result in the same value.
    11  // That lets us the magic number to determine the endianness.
    12  type PCLnTabMagic uint32
    13  
    14  const (
    15  	// Initial PCLnTabMagic value used in Go 1.2 through Go 1.15.
    16  	Go12PCLnTabMagic PCLnTabMagic = 0xfffffffb
    17  	// PCLnTabMagic value used in Go 1.16 through Go 1.17.
    18  	// Several fields added to header (CL 241598).
    19  	Go116PCLnTabMagic PCLnTabMagic = 0xfffffffa
    20  	// PCLnTabMagic value used in Go 1.18 through Go 1.19.
    21  	// Entry PC of func data changed from address to offset (CL 351463).
    22  	Go118PCLnTabMagic PCLnTabMagic = 0xfffffff0
    23  	// PCLnTabMagic value used in Go 1.20 and later.
    24  	// A ":" was added to generated symbol names (#37762).
    25  	Go120PCLnTabMagic PCLnTabMagic = 0xfffffff1
    26  
    27  	// CurrentPCLnTabMagic is the value emitted by the current toolchain.
    28  	// This is written by the linker to the pcHeader and read by the
    29  	// runtime and debug/gosym (and external tools like Delve).
    30  	//
    31  	// Change this value when updating the pclntab version.
    32  	// Changing this exported value is OK because is an
    33  	// internal package.
    34  	CurrentPCLnTabMagic = Go120PCLnTabMagic
    35  )
    36  
    37  // A FuncFlag records bits about a function, passed to the runtime.
    38  type FuncFlag uint8
    39  
    40  const (
    41  	// FuncFlagTopFrame indicates a function that appears at the top of its stack.
    42  	// The traceback routine stop at such a function and consider that a
    43  	// successful, complete traversal of the stack.
    44  	// Examples of TopFrame functions include goexit, which appears
    45  	// at the top of a user goroutine stack, and mstart, which appears
    46  	// at the top of a system goroutine stack.
    47  	FuncFlagTopFrame FuncFlag = 1 << iota
    48  
    49  	// FuncFlagSPWrite indicates a function that writes an arbitrary value to SP
    50  	// (any write other than adding or subtracting a constant amount).
    51  	// The traceback routines cannot encode such changes into the
    52  	// pcsp tables, so the function traceback cannot safely unwind past
    53  	// SPWrite functions. Stopping at an SPWrite function is considered
    54  	// to be an incomplete unwinding of the stack. In certain contexts
    55  	// (in particular garbage collector stack scans) that is a fatal error.
    56  	FuncFlagSPWrite
    57  
    58  	// FuncFlagAsm indicates that a function was implemented in assembly.
    59  	FuncFlagAsm
    60  )
    61  
    62  // A FuncID identifies particular functions that need to be treated
    63  // specially by the runtime.
    64  // Note that in some situations involving plugins, there may be multiple
    65  // copies of a particular special runtime function.
    66  type FuncID uint8
    67  
    68  const (
    69  	// If you add a FuncID, you probably also want to add an entry to the map in
    70  	// ../../cmd/internal/objabi/funcid.go
    71  
    72  	FuncIDNormal FuncID = iota // not a special function
    73  	FuncID_abort
    74  	FuncID_asmcgocall
    75  	FuncID_asyncPreempt
    76  	FuncID_cgocallback
    77  	FuncID_corostart
    78  	FuncID_debugCallV2
    79  	FuncID_gcBgMarkWorker
    80  	FuncID_goexit
    81  	FuncID_gogo
    82  	FuncID_gopanic
    83  	FuncID_handleAsyncEvent
    84  	FuncID_mcall
    85  	FuncID_morestack
    86  	FuncID_mstart
    87  	FuncID_panicwrap
    88  	FuncID_rt0_go
    89  	FuncID_runtime_main
    90  	FuncID_runFinalizers
    91  	FuncID_runCleanups
    92  	FuncID_sigpanic
    93  	FuncID_systemstack
    94  	FuncID_systemstack_switch
    95  	FuncIDWrapper // any autogenerated code (hash/eq algorithms, method wrappers, etc.)
    96  )
    97  
    98  // ArgsSizeUnknown is set in Func.argsize to mark all functions
    99  // whose argument size is unknown (C vararg functions, and
   100  // assembly code without an explicit specification).
   101  // This value is generated by the compiler, assembler, or linker.
   102  const ArgsSizeUnknown = -0x80000000
   103  
   104  // IDs for PCDATA and FUNCDATA tables in Go binaries.
   105  //
   106  // These must agree with ../../../runtime/funcdata.h.
   107  const (
   108  	PCDATA_UnsafePoint   = 0
   109  	PCDATA_StackMapIndex = 1
   110  	PCDATA_InlTreeIndex  = 2
   111  	PCDATA_ArgLiveIndex  = 3
   112  	PCDATA_PanicBounds   = 4
   113  
   114  	FUNCDATA_ArgsPointerMaps    = 0
   115  	FUNCDATA_LocalsPointerMaps  = 1
   116  	FUNCDATA_StackObjects       = 2
   117  	FUNCDATA_InlTree            = 3
   118  	FUNCDATA_OpenCodedDeferInfo = 4
   119  	FUNCDATA_ArgInfo            = 5
   120  	FUNCDATA_ArgLiveInfo        = 6
   121  	FUNCDATA_WrapInfo           = 7
   122  )
   123  
   124  // Special values for the PCDATA_UnsafePoint table.
   125  const (
   126  	UnsafePointSafe   = -1 // Safe for async preemption
   127  	UnsafePointUnsafe = -2 // Unsafe for async preemption
   128  
   129  	// UnsafePointRestart1(2) apply on a sequence of instructions, within
   130  	// which if an async preemption happens, we should back off the PC
   131  	// to the start of the sequence when resuming.
   132  	// We need two so we can distinguish the start/end of the sequence
   133  	// in case that two sequences are next to each other.
   134  	UnsafePointRestart1 = -3
   135  	UnsafePointRestart2 = -4
   136  
   137  	// Like UnsafePointRestart1, but back to function entry if async preempted.
   138  	UnsafePointRestartAtEntry = -5
   139  )
   140  
   141  const MINFUNC = 16 // minimum size for a function
   142  
   143  const FuncTabBucketSize = 256 * MINFUNC // size of bucket in the pc->func lookup table
   144
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