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// AsmJit - Machine code generation for C++
//
// * Official AsmJit Home Page: https://asmjit.com
// * Official Github Repository: https://github.com/asmjit/asmjit
//
// Copyright (c) 2008-2020 The AsmJit Authors
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would be
// appreciated but is not required.
// 2. Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
// 3. This notice may not be removed or altered from any source distribution.
// ----------------------------------------------------------------------------
// This is a working example that demonstrates how multiple sections can be
// used in a JIT-based code generator. It shows also the necessary tooling
// that is expected to be done by the user when the feature is used. It's
// important to handle the following cases:
//
// - Assign offsets to sections when the code generation is finished.
// - Tell the CodeHolder to resolve unresolved links and check whether
// all links were resolved.
// - Relocate the code
// - Copy the code to the destination address.
// ----------------------------------------------------------------------------
#include <asmjit/core.h>
#if defined(ASMJIT_BUILD_X86) && ASMJIT_ARCH_X86
#include <asmjit/x86.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace asmjit;
// The generated function is very simple, it only accesses the built-in data
// (from .data section) at the index as provided by its first argument. This
// data is inlined into the resulting function so we can use it this array
// for verification that the function returns correct values.
static const uint8_t dataArray[] = { 2, 9, 4, 7, 1, 3, 8, 5, 6, 0 };
static void fail(const char* message, Error err) {
printf("%s: %s\n", message, DebugUtils::errorAsString(err));
exit(1);
}
int main() {
printf("AsmJit X86 Sections Test\n\n");
Environment env = hostEnvironment();
JitAllocator allocator;
#ifndef ASMJIT_NO_LOGGING
FileLogger logger(stdout);
logger.setIndentation(FormatOptions::kIndentationCode, 2);
#endif
CodeHolder code;
code.init(env);
#ifndef ASMJIT_NO_LOGGING
code.setLogger(&logger);
#endif
Section* dataSection;
Error err = code.newSection(&dataSection, ".data", SIZE_MAX, 0, 8);
if (err) {
fail("Failed to create a .data section", err);
}
else {
printf("Generating code:\n");
x86::Assembler a(&code);
x86::Gp idx = a.zax();
x86::Gp addr = a.zcx();
Label data = a.newLabel();
FuncDetail func;
func.init(FuncSignatureT<size_t, size_t>(CallConv::kIdHost), code.environment());
FuncFrame frame;
frame.init(func);
frame.addDirtyRegs(idx, addr);
FuncArgsAssignment args(&func);
args.assignAll(idx);
args.updateFuncFrame(frame);
frame.finalize();
a.emitProlog(frame);
a.emitArgsAssignment(frame, args);
a.lea(addr, x86::ptr(data));
a.movzx(idx, x86::byte_ptr(addr, idx));
a.emitEpilog(frame);
a.section(dataSection);
a.bind(data);
a.embed(dataArray, sizeof(dataArray));
}
// Manually change he offsets of each section, start at 0. This code is very
// similar to what `CodeHolder::flatten()` does, however, it's shown here
// how to do it explicitly.
printf("\nCalculating section offsets:\n");
uint64_t offset = 0;
for (Section* section : code.sectionsByOrder()) {
offset = Support::alignUp(offset, section->alignment());
section->setOffset(offset);
offset += section->realSize();
printf(" [0x%08X %s] {Id=%u Size=%u}\n",
uint32_t(section->offset()),
section->name(),
section->id(),
uint32_t(section->realSize()));
}
size_t codeSize = size_t(offset);
printf(" Final code size: %zu\n", codeSize);
// Resolve cross-section links (if any). On 32-bit X86 this is not necessary
// as this is handled through relocations as the addressing is different.
if (code.hasUnresolvedLinks()) {
printf("\nResolving cross-section links:\n");
printf(" Before 'resolveUnresolvedLinks()': %zu\n", code.unresolvedLinkCount());
err = code.resolveUnresolvedLinks();
if (err)
fail("Failed to resolve cross-section links", err);
printf(" After 'resolveUnresolvedLinks()': %zu\n", code.unresolvedLinkCount());
}
// Allocate memory for the function and relocate it there.
void* roPtr;
void* rwPtr;
err = allocator.alloc(&roPtr, &rwPtr, codeSize);
if (err)
fail("Failed to allocate executable memory", err);
// Relocate to the base-address of the allocated memory.
code.relocateToBase(uint64_t(uintptr_t(roPtr)));
// Copy the flattened code into `mem.rw`. There are two ways. You can either copy
// everything manually by iterating over all sections or use `copyFlattenedData`.
// This code is similar to what `copyFlattenedData(p, codeSize, 0)` would do:
for (Section* section : code.sectionsByOrder())
memcpy(static_cast<uint8_t*>(rwPtr) + size_t(section->offset()), section->data(), section->bufferSize());
// Execute the function and test whether it works.
typedef size_t (*Func)(size_t idx);
Func fn = (Func)roPtr;
printf("\n");
if (fn(0) != dataArray[0] ||
fn(3) != dataArray[3] ||
fn(6) != dataArray[6] ||
fn(9) != dataArray[9] ) {
printf("Failure:\n The generated function returned incorrect result(s)\n");
return 1;
}
printf("Success:\n The generated function returned expected results\n");
return 0;
}
#else
int main() {
printf("AsmJit X86 Sections Test is disabled on non-x86 host\n\n");
return 0;
}
#endif
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