1 // [AsmJit]
2 // Machine Code Generation for C++.
3 //
4 // [License]
5 // Zlib - See LICENSE.md file in the package.
6
7 // This is a working example that demonstrates how multiple sections can be
8 // used in a JIT-based code generator. It shows also the necessary tooling
9 // that is expected to be done by the user when the feature is used. It's
10 // important to handle the following cases:
11 //
12 // - Assign offsets to sections when the code generation is finished.
13 // - Tell the CodeHolder to resolve unresolved links and check whether
14 // all links were resolved.
15 // - Relocate the code
16 // - Copy the code to the location you want.
17
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include <string.h>
21
22 #include "./asmjit.h"
23
24 using namespace asmjit;
25
26 // The generated function is very simple, it only accesses the built-in data
27 // (from .data section) at the index as provided by its first argument. This
28 // data is inlined into the resulting function so we can use it this array
29 // for verification that the function returns correct values.
30 static const uint8_t dataArray[] = { 2, 9, 4, 7, 1, 3, 8, 5, 6, 0 };
31
fail(const char * message,Error err)32 static void fail(const char* message, Error err) {
33 printf("%s: %s\n", message, DebugUtils::errorAsString(err));
34 exit(1);
35 }
36
main(int argc,char * argv[])37 int main(int argc, char* argv[]) {
38 ASMJIT_UNUSED(argc);
39 ASMJIT_UNUSED(argv);
40
41 CodeInfo codeInfo(ArchInfo::kIdHost);
42 JitAllocator allocator;
43
44 FileLogger logger(stdout);
45 logger.setIndentation(FormatOptions::kIndentationCode, 2);
46
47 CodeHolder code;
48 code.init(codeInfo);
49 code.setLogger(&logger);
50
51 Section* section;
52 Error err = code.newSection(§ion, ".data", SIZE_MAX, 0, 8);
53
54 if (err) {
55 fail("Failed to create a .data section", err);
56 }
57 else {
58 printf("Generating code:\n");
59 x86::Assembler a(&code);
60 x86::Gp idx = a.zax();
61 x86::Gp addr = a.zcx();
62
63 Label data = a.newLabel();
64
65 FuncDetail func;
66 func.init(FuncSignatureT<size_t, size_t>(CallConv::kIdHost));
67
68 FuncFrame frame;
69 frame.init(func);
70 frame.addDirtyRegs(idx, addr);
71
72 FuncArgsAssignment args(&func);
73 args.assignAll(idx);
74 args.updateFuncFrame(frame);
75 frame.finalize();
76
77 a.emitProlog(frame);
78 a.emitArgsAssignment(frame, args);
79
80 a.lea(addr, x86::ptr(data));
81 a.movzx(idx, x86::byte_ptr(addr, idx));
82
83 a.emitEpilog(frame);
84
85 a.section(section);
86 a.bind(data);
87
88 a.embed(dataArray, sizeof(dataArray));
89 }
90
91 // Manually change he offsets of each section, start at 0. This code is very
92 // similar to what `CodeHolder::flatten()` does, however, it's shown here
93 // how to do it explicitly.
94 printf("\nCalculating section offsets:\n");
95 uint64_t offset = 0;
96 for (Section* section : code.sections()) {
97 offset = Support::alignUp(offset, section->alignment());
98 section->setOffset(offset);
99 offset += section->realSize();
100
101 printf(" [0x%08X %s] {Id=%u Size=%u}\n",
102 uint32_t(section->offset()),
103 section->name(),
104 section->id(),
105 uint32_t(section->realSize()));
106 }
107 size_t codeSize = size_t(offset);
108 printf(" Final code size: %zu\n", codeSize);
109
110 // Resolve cross-section links (if any). On 32-bit X86 this is not necessary
111 // as this is handled through relocations as the addressing is different.
112 if (code.hasUnresolvedLinks()) {
113 printf("\nResolving cross-section links:\n");
114 printf(" Before 'resolveUnresolvedLinks()': %zu\n", code.unresolvedLinkCount());
115
116 err = code.resolveUnresolvedLinks();
117 if (err)
118 fail("Failed to resolve cross-section links", err);
119 printf(" After 'resolveUnresolvedLinks()': %zu\n", code.unresolvedLinkCount());
120 }
121
122 // Allocate memory for the function and relocate it there.
123 void* roPtr;
124 void* rwPtr;
125 err = allocator.alloc(&roPtr, &rwPtr, codeSize);
126 if (err)
127 fail("Failed to allocate executable memory", err);
128
129 // Relocate to the base-address of the allocated memory.
130 code.relocateToBase(uint64_t(uintptr_t(roPtr)));
131
132 // Copy the flattened code into `mem.rw`. There are two ways. You can either copy
133 // everything manually by iterating over all sections or use `copyFlattenedData`.
134 // This code is similar to what `copyFlattenedData(p, codeSize, 0)` would do:
135 for (Section* section : code.sections())
136 memcpy(static_cast<uint8_t*>(rwPtr) + size_t(section->offset()), section->data(), section->bufferSize());
137
138 // Execute the function and test whether it works.
139 typedef size_t (*Func)(size_t idx);
140 Func fn = (Func)roPtr;
141
142 printf("\nTesting the generated function:\n");
143 if (fn(0) != dataArray[0] ||
144 fn(3) != dataArray[3] ||
145 fn(6) != dataArray[6] ||
146 fn(9) != dataArray[9] ) {
147 printf(" [FAILED] The generated function returned incorrect result(s)\n");
148 return 1;
149 }
150 else {
151 printf(" [PASSED] The generated function returned expected results\n");
152 }
153
154 allocator.release((void*)fn);
155 return 0;
156 }
157