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
5package abi
6
7// A FuncFlag records bits about a function, passed to the runtime.
8type FuncFlag uint8
9
10const (
11	// FuncFlagTopFrame indicates a function that appears at the top of its stack.
12	// The traceback routine stop at such a function and consider that a
13	// successful, complete traversal of the stack.
14	// Examples of TopFrame functions include goexit, which appears
15	// at the top of a user goroutine stack, and mstart, which appears
16	// at the top of a system goroutine stack.
17	FuncFlagTopFrame FuncFlag = 1 << iota
18
19	// FuncFlagSPWrite indicates a function that writes an arbitrary value to SP
20	// (any write other than adding or subtracting a constant amount).
21	// The traceback routines cannot encode such changes into the
22	// pcsp tables, so the function traceback cannot safely unwind past
23	// SPWrite functions. Stopping at an SPWrite function is considered
24	// to be an incomplete unwinding of the stack. In certain contexts
25	// (in particular garbage collector stack scans) that is a fatal error.
26	FuncFlagSPWrite
27
28	// FuncFlagAsm indicates that a function was implemented in assembly.
29	FuncFlagAsm
30)
31
32// A FuncID identifies particular functions that need to be treated
33// specially by the runtime.
34// Note that in some situations involving plugins, there may be multiple
35// copies of a particular special runtime function.
36type FuncID uint8
37
38const (
39	// If you add a FuncID, you probably also want to add an entry to the map in
40	// ../../cmd/internal/objabi/funcid.go
41
42	FuncIDNormal FuncID = iota // not a special function
43	FuncID_abort
44	FuncID_asmcgocall
45	FuncID_asyncPreempt
46	FuncID_cgocallback
47	FuncID_corostart
48	FuncID_debugCallV2
49	FuncID_gcBgMarkWorker
50	FuncID_goexit
51	FuncID_gogo
52	FuncID_gopanic
53	FuncID_handleAsyncEvent
54	FuncID_mcall
55	FuncID_morestack
56	FuncID_mstart
57	FuncID_panicwrap
58	FuncID_rt0_go
59	FuncID_runfinq
60	FuncID_runtime_main
61	FuncID_sigpanic
62	FuncID_systemstack
63	FuncID_systemstack_switch
64	FuncIDWrapper // any autogenerated code (hash/eq algorithms, method wrappers, etc.)
65)
66
67// ArgsSizeUnknown is set in Func.argsize to mark all functions
68// whose argument size is unknown (C vararg functions, and
69// assembly code without an explicit specification).
70// This value is generated by the compiler, assembler, or linker.
71const ArgsSizeUnknown = -0x80000000
72
73// IDs for PCDATA and FUNCDATA tables in Go binaries.
74//
75// These must agree with ../../../runtime/funcdata.h.
76const (
77	PCDATA_UnsafePoint   = 0
78	PCDATA_StackMapIndex = 1
79	PCDATA_InlTreeIndex  = 2
80	PCDATA_ArgLiveIndex  = 3
81
82	FUNCDATA_ArgsPointerMaps    = 0
83	FUNCDATA_LocalsPointerMaps  = 1
84	FUNCDATA_StackObjects       = 2
85	FUNCDATA_InlTree            = 3
86	FUNCDATA_OpenCodedDeferInfo = 4
87	FUNCDATA_ArgInfo            = 5
88	FUNCDATA_ArgLiveInfo        = 6
89	FUNCDATA_WrapInfo           = 7
90)
91
92// Special values for the PCDATA_UnsafePoint table.
93const (
94	UnsafePointSafe   = -1 // Safe for async preemption
95	UnsafePointUnsafe = -2 // Unsafe for async preemption
96
97	// UnsafePointRestart1(2) apply on a sequence of instructions, within
98	// which if an async preemption happens, we should back off the PC
99	// to the start of the sequence when resuming.
100	// We need two so we can distinguish the start/end of the sequence
101	// in case that two sequences are next to each other.
102	UnsafePointRestart1 = -3
103	UnsafePointRestart2 = -4
104
105	// Like UnsafePointRestart1, but back to function entry if async preempted.
106	UnsafePointRestartAtEntry = -5
107)
108
109const MINFUNC = 16 // minimum size for a function
110
111const FuncTabBucketSize = 256 * MINFUNC // size of bucket in the pc->func lookup table
112