LLVM
LLVM(Low Level Virtual Machine)是苹果公司的开源编译器框架, 包含包括Clang在内的一系列编译相关工具, 于2000年左右开发, LLVM/Clang从XCode8起作为XCode默认编译器,
LLVM作为以下语言的开发工具链: C, C++, Objective-C, Swift, Ruby, Python, Haskell, Rust, D, PHP, Pure, Lua, Julia. https://llvm.org
相比同样庞大但臃肿的GCC, LLVM的模块化设计更利于扩展和维护, 因此LLVM取代GCC是必然趋势, 这一点不会因特殊环境下的不兼容和BUG及某些人的意志而改变.
LLVM包含如下组件:
- Clang, 用于做C/C++/Objective-C的编译前端
- LLDB, 调试器
- libc++, 提供c++基础库
- compiler-rt
- MLIR
- OpenMP
- libclc
- klee
- LLD 链接器
- BOLT
第三方:
- rustc, 用于rust的编译前端
- swiftc, 用于swift的编译前端
- codon, 用于python的编译前端
历史更新功能点
- 由Chris Lattner于2000创建
- LLVM1.0(2003), 首次公开发布
- LLVM3.0(2012), 引入了新的JIT编译器, 支持C++11, 基于SSA的内存安全转换, 全局ISel重构
- LLVM3.7(2015), 支持OpenMP3.1, Clang Static Analyzer增强,AArch64支持
- LLVM5.0(2016), 支持C++14, 引入了新的代码分析和优化技术
- LLVM9.0(2019), 支持C++17, JIT支持WebAssembly, 优化RISC-V, 优化IR
- LLVM12.0(2021), 支持C++20, 引入LTO优化, 支持arm64e
XCode与LLVM版本对应
| XCode |
LLVM |
| 11.x |
11 |
| 12.x |
12 |
| 13.x |
13 |
| 14.x |
14 |
| 15.x |
15 |
Hikari模块化
https://github.com/lich4/indep_hikari
原链接: https://github.com/61bcdefg/Hikari-LLVM15
本项目是笔者研究Ollvm的基础, 为以后的项目做准备
背景
- 由于LLVM代码量巨大, 编译一次需要小时为单位(Hikari原作者就有这个困扰), 在这种情况下去开发/调试/测试Ollvm会非常艰难, 因此笔者将Hikari独立化为动态库以提高编译速度
- 为什么不使用LLVM-Pass? 因为Hikari与之并不兼容, 所以无法用LLVM-Pass来做, 但基于LLVM-Pass的Ollvm也有人在做
- 如果不以研究为目的, 只是产出二进制则直接用Gihub Action即可
修改LLVM
// 以19.0.0为基础 llvm/lib/Passes/PassBuilderPipelines.cpp
...
#include <dlfcn.h>
...
ModulePassManager PassBuilder::buildO0DefaultPipeline(OptimizationLevel Level, bool LTOPreLink) {
...
invokeOptimizerLastEPCallbacks(MPM, Level);
// add
if (!LTOPreLink) {
dlopen("hikari.dylib", RTLD_NOW);
void* sym = dlsym(RTLD_DEFAULT, "_Z13hikariAddPassRN4llvm11PassManagerINS_6ModuleENS_15AnalysisManagerIS1_JEEEJEEE");
void (*hikariAddPass_)(ModulePassManager& man) = (__typeof(hikariAddPass_))sym;
hikariAddPass_(MPM);
}
if (LTOPreLink)
addRequiredLTOPreLinkPasses(MPM);
MPM.addPass(createModuleToFunctionPassAdaptor(AnnotationRemarksPass()));
return MPM;
}
编译
# 先编译llvm
cmake -S llvm -B Build -DLLVM_ENABLE_PROJECTS=clang -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_CREATE_XCODE_TOOLCHAIN=On -DCMAKE_INSTALL_PREFIX=$PWD/install
cmake --build build -j3
# 再编译hikari
cd Obfuscation
make -j3
cp -f hikari.dylib ../Build/lib/
注意: 如果需要编译其他组件, 需要指定LLVM_ENABLE_PROJECTS, 目前支持clang;clang-tools-extra;lld;compiler-rt;lldb;openmp;mlir, 如-DLLVM_ENABLE_PROJECTS="clang;lld".
注意: 如果要编译运行时, 需要指定LLVM_ENABLE_RUNTIMES, 目前支持libc;libunwind;libcxxabi;pstl;libcxx;compiler-rt;openmp;llvm-libgcc.
注意: Hikari独立化后暂不支持mllvm参数
LLVM IR初探
什么是IR? IR(Intermediate Representation), 是一种LLVM定义的介于源码和汇编的中间语言, 语法类似于汇编. IR主要用于解决跨平台编译的问题, 同时也能解决优化/混淆/扩展问题
IR手册 https://llvm.org/docs/LangRef.html
- llc 将bitcode转换为asm/obj
- lld 将多个bitcode/obj编译为二进制
- lli bitcode解释器
- opt 优化bitcode
- llvm-ar 操作archive
- llvm-as 将ll转换为bitcode, ll为人类可读字节码格式
- llvm-cxxfilt c++修饰名转普通
- llvm-dis bitcode转ll
- llvm-extract 从bitcode提取函数
- llvm-link 将多个bitcode合并为一个bitcode
- clang -emit-llvm -c 源码编译为bitcode
- clang -emit-llvm -S 源码编译为ll
第三方:
swiftc -emit-assembly /tmp/1.swift -o /tmp/1.bc Swift源码编译为汇编swiftc -emit-bc /tmp/1.swift -o /tmp/1.bc Swift源码编译为bitcodeswiftc -emit-ir /tmp/1.swift -o /tmp/1.ll Swift源码编译为llcargo rustc -- --emit=asm或rustc --emit=asm 1.rs Rust源码编译为汇编cargo rustc -- --emit=llvm-bc或rustc --emit=llvm-bc 1.rs Rust源码编译为bitcodecargo rustc -- --emit=llvm-ir或rustc --emit=llvm-ir 1.rs Rust源码编译为llcodon build -llvm 1.py Python源码编译为ll
测试用例:
// 1.cpp
#include <stdio.h>
int main(int argc, char** argv) {
printf("Hello World!\n");
return 0;
}
源码交叉编译为bitcode/ll
# for MacOS x86_64
./clang -isysroot `xcrun --sdk macosx --show-sdk-path` -arch x86_64 -emit-llvm -c /tmp/1.cpp --output=/tmp/1.bc
./clang -isysroot `xcrun --sdk macosx --show-sdk-path` -arch x86_64 -emit-llvm -S /tmp/1.cpp --output=/tmp/1.ll
# 如果要用XCode自带clang需使用xcrun, 以下同, 不建议用XCode clang, 因为不同版本Clang/llc/lld/lli互相不兼容, 且XCode不提供llc/lld/lli
xcrun --sdk macosx clang -arch x86_64 -emit-llvm -c /tmp/1.cpp --output=/tmp/1.bc
; ModuleID = '/tmp/1.cpp'
source_filename = "/tmp/1.cpp"
target datalayout = "e-m
-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx11.3.0"
@.str = private unnamed_addr constant [14 x i8] c"Hello World!\0A\00", align 1
; Function Attrs: mustprogress noinline norecurse optnone ssp uwtable
define noundef i32 @main(i32 noundef %0, ptr noundef %1) #0 {
%3 = alloca i32, align 4
%4 = alloca i32, align 4
%5 = alloca ptr, align 8
store i32 0, ptr %3, align 4
store i32 %0, ptr %4, align 4
store ptr %1, ptr %5, align 8
%6 = call i32 (ptr, ...) @printf(ptr noundef @.str)
ret i32 0
}
declare i32 @printf(ptr noundef, ...) #1
attributes #0 = { mustprogress noinline norecurse optnone ssp uwtable "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cmov,+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "tune-cpu"="generic" }
attributes #1 = { "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cmov,+cx16,+cx8,+fxsr,+mmx,+sahf,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "tune-cpu"="generic" }
!llvm.module.flags = !{!0, !1, !2, !3, !4}
!llvm.ident = !{!5}
!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 11, i32 3]}
!1 = !{i32 1, !"wchar_size", i32 4}
!2 = !{i32 8, !"PIC Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{i32 7, !"frame-pointer", i32 2}
!5 = !{!"clang version 19.0.0git"}
# for iOS arm64
./clang -isysroot `xcrun --sdk iphoneos --show-sdk-path` -arch arm64 -emit-llvm -c /tmp/1.cpp --output=/tmp/1.bc
./clang -isysroot `xcrun --sdk iphoneos --show-sdk-path` -arch arm64 -emit-llvm -S /tmp/1.cpp --output=/tmp/1.ll
; ModuleID = '/tmp/1.cpp'
source_filename = "/tmp/1.cpp"
target datalayout = "e-m-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "arm64-apple-ios14.5.0"
@.str = private unnamed_addr constant [14 x i8] c"Hello World!\0A\00", align 1
; Function Attrs: mustprogress noinline norecurse optnone ssp uwtable(sync)
define noundef i32 @main(i32 noundef %0, ptr noundef %1) #0 {
%3 = alloca i32, align 4
%4 = alloca i32, align 4
%5 = alloca ptr, align 8
store i32 0, ptr %3, align 4
store i32 %0, ptr %4, align 4
store ptr %1, ptr %5, align 8
%6 = call i32 (ptr, ...) @printf(ptr noundef @.str)
ret i32 0
}
declare i32 @printf(ptr noundef, ...) #1
attributes #0 = { mustprogress noinline norecurse optnone ssp uwtable(sync) "frame-pointer"="non-leaf" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-a7" "target-features"="+aes,+fp-armv8,+neon,+perfmon,+sha2,+v8a,+zcm,+zcz" }
attributes #1 = { "frame-pointer"="non-leaf" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-a7" "target-features"="+aes,+fp-armv8,+neon,+perfmon,+sha2,+v8a,+zcm,+zcz" }
!llvm.module.flags = !{!0, !1, !2, !3, !4}
!llvm.ident = !{!5}
!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 14, i32 5]}
!1 = !{i32 1, !"wchar_size", i32 4}
!2 = !{i32 8, !"PIC Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 1}
!4 = !{i32 7, !"frame-pointer", i32 1}
!5 = !{!"clang version 19.0.0git"}; ModuleID = '/tmp/1.cpp'
source_filename = "/tmp/1.cpp"
target datalayout = "e-m-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "arm64-apple-ios14.5.0"
@.str = private unnamed_addr constant [14 x i8] c"Hello World!\0A\00", align 1
; Function Attrs: mustprogress noinline norecurse optnone ssp uwtable(sync)
define noundef i32 @main(i32 noundef %0, ptr noundef %1) #0 {
%3 = alloca i32, align 4
%4 = alloca i32, align 4
%5 = alloca ptr, align 8
store i32 0, ptr %3, align 4
store i32 %0, ptr %4, align 4
store ptr %1, ptr %5, align 8
%6 = call i32 (ptr, ...) @printf(ptr noundef @.str)
ret i32 0
}
declare i32 @printf(ptr noundef, ...) #1
attributes #0 = { mustprogress noinline norecurse optnone ssp uwtable(sync) "frame-pointer"="non-leaf" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-a7" "target-features"="+aes,+fp-armv8,+neon,+perfmon,+sha2,+v8a,+zcm,+zcz" }
attributes #1 = { "frame-pointer"="non-leaf" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-a7" "target-features"="+aes,+fp-armv8,+neon,+perfmon,+sha2,+v8a,+zcm,+zcz" }
!llvm.module.flags = !{!0, !1, !2, !3, !4}
!llvm.ident = !{!5}
!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 14, i32 5]}
!1 = !{i32 1, !"wchar_size", i32 4}
!2 = !{i32 8, !"PIC Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 1}
!4 = !{i32 7, !"frame-pointer", i32 1}
!5 = !{!"clang version 19.0.0git"}
bitcode/ll编译为asm/obj
./llc --filetype=asm /tmp/1.ll -o /tmp/1.asm
./llc --filetype=obj /tmp/1.ll -o /tmp/1.obj
./llc --filetype=asm /tmp/1.bc -o /tmp/1.asm
./llc --filetype=obj /tmp/1.bc -o /tmp/1.obj
.section __TEXT,__text,regular,pure_instructions
.build_version ios, 14, 5 sdk_version 14, 5
.globl _main ; -- Begin function main
.p2align 2
_main: ; @main
.cfi_startproc
; %bb.0:
sub sp, sp, #32
stp x29, x30, [sp, #16] ; 16-byte Folded Spill
add x29, sp, #16
.cfi_def_cfa w29, 16
.cfi_offset w30, -8
.cfi_offset w29, -16
stur wzr, [x29, #-4]
str w0, [sp, #8]
str x1, [sp]
adrp x0, l_.str@PAGE
add x0, x0, l_.str@PAGEOFF
bl _printf
mov w0, #0 ; =0x0
ldp x29, x30, [sp, #16] ; 16-byte Folded Reload
add sp, sp, #32
ret
.cfi_endproc
; -- End function
.section __TEXT,__cstring,cstring_literals
l_.str: ; @.str
.asciz "Hello World!\n"
.subsections_via_symbols
bitcode编译为可执行程序
lld是通用程序, 不同平台需要调用不同二进制
- Unix: ld.lld
- macOS: ld64.lld
- Windows: lld-link
- WebAssembly: wasm-ld
./ld64.lld -arch arm64 -platform_version ios 12.0 14.5 -dylib /tmp/1.bc -o /tmp/1.exe
运行bitcode
./lli /tmp/1.ll
./lli /tmp/1.bc
# 均输出"Hello World!"
IR指令
Instruction
UnaryInstruction 一元指令
UnaryOperator 一元操作
CastInst 强制转换
PossiblyNonNegInst 非负指令
BinaryOperator 二进制操作
PossiblyDisjointInst
CmpInst 比较操作
CallBase 调用操作
FuncletPadInst
Super
AllocaInst UnaryInstruction An instruction to allocate memory on the stack.
LoadInst UnaryInstruction An instruction for reading from memory. This uses the SubclassData
field in Value to store whether or not the load is volatile.
StoreInst Instruction An instruction for storing to memory.
FenceInst Instruction An instruction for ordering other memory operations.
AtomicCmpXchgInst Instruction An instruction that atomically checks whether a specified value
is in a memory location, and, if it is, stores a new value there.
The value returned by this instruction is a pair containing the
original value as first element, and an i1 indicating success
(true) or failure (false) as second element.
AtomicRMWInst Instruction An instruction that atomically reads a memory location, combines
it with another value, and then stores the result back. Returns
the old value.
GetElementPtrInst Instruction An instruction for type-safe pointer arithmetic to access elements
of arrays and structs
ICmpInst CmpInst This instruction compares its operands according to the predicate
given to the constructor. It only operates on integers or pointers.
The operands must be identical types. Represent an integer comparison
operator.
FCmpInst CmpInst This instruction compares its operands according to the predicate
given to the constructor. It only operates on floating point values
or packed vectors of floating point values. The operands must be
identical types. Represents a floating point comparison operator.
CallInst CallBase This class represents a function call, abstracting a target machine's
calling convention. This class uses low bit of the SubClassData
field to indicate whether or not this is a tail call. The rest
of the bits hold the calling convention of the call.
SelectInst Instruction This class represents the LLVM 'select' instruction.
VAArgInst UnaryInstruction This class represents the va_arg llvm instruction, which returns
an argument of the specified type given a va_list and increments
that list
ExtractElementInst Instruction This instruction extracts a single (scalar) element from a VectorType value
InsertElementInst Instruction This instruction inserts a single (scalar) element into a VectorType value
ShuffleVectorInst Instruction This instruction constructs a fixed permutation of two input vectors.
For each element of the result vector, the shuffle mask selects an
element from one of the input vectors to copy to the result.
Non-negative elements in the mask represent an index into the
concatenated pair of input vectors. PoisonMaskElem (-1) specifies
that the result element is poison. For scalable vectors, all the
elements of the mask must be 0 or -1. This requirement may be
relaxed in the future.
ExtractValueInst UnaryInstruction This instruction extracts a struct member or array element value
from an aggregate value.
InsertValueInst Instruction This instruction inserts a struct field of array element value
into an aggregate value.
PHINode Instruction PHINode - The PHINode class is used to represent the magical mystical
PHI node, that can not exist in nature, but can be synthesized in a
computer scientist's overactive imagination.
LandingPadInst Instruction The landingpad instruction holds all of the information necessary
to generate correct exception handling. The landingpad instruction
cannot be moved from the top of a landing pad block, which itself
is accessible only from the 'unwind' edge of an invoke. This uses
the SubclassData field in Value to store whether or not the landingpad
is a cleanup.
ReturnInst Instruction Return a value (possibly void), from a function. Execution does
not continue in this function any longer.
BranchInst Instruction Conditional or Unconditional Branch instruction.
SwitchInst Instruction Multiway switch.
IndirectBrInst Instruction Indirect Branch Instruction.
InvokeInst CallBase Invoke instruction. The SubclassData field is used to hold the
calling convention of the call.
CallBrInst CallBase CallBr instruction, tracking function calls that may not return
control but instead transfer it to a third location. The SubclassData
field is used to hold the calling convention of the call.
ResumeInst Instruction Resume the propagation of an exception.
CatchSwitchInst Instruction
CleanupPadInst FuncletPadInst
CatchPadInst FuncletPadInst
CatchReturnInst Instruction
CleanupReturnInst Instruction
UnreachableInst Instruction This function has undefined behavior. In particular, the presence
of this instruction indicates some higher level knowledge that
the end of the block cannot be reached.
TruncInst CastInst This class represents a truncation of integer types.
ZExtInst CastInst This class represents zero extension of integer types.
SExtInst CastInst This class represents a sign extension of integer types.
FPTruncInst CastInst This class represents a truncation of floating point types.
FPExtInst CastInst This class represents an extension of floating point types.
UIToFPInst CastInst This class represents a cast unsigned integer to floating point.
SIToFPInst CastInst This class represents a cast from signed integer to floating point.
FPToUIInst CastInst This class represents a cast from floating point to unsigned integer.
FPToSIInst CastInst This class represents a cast from floating point to signed integer.
IntToPtrInst CastInst This class represents a cast from an integer to a pointer.
PtrToIntInst CastInst This class represents a cast from a pointer to an integer.
BitCastInst CastInst This class represents a no-op cast from one type to another.
AddrSpaceCastInst CastInst This class represents a conversion between pointers from one address
space to another.
FreezeInst UnaryInstruction This class represents a freeze function that returns random concrete
value if an operand is either a poison value or an undef value
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