[cfe-dev] JIT doens't resolve address - Resolve obj-Addresses?
Lang Hames via cfe-dev
cfe-dev at lists.llvm.org
Mon May 1 11:16:12 PDT 2017
Hi Björn,
I tried using your code and now it works! I'm happy and surprised!
Oh - I missed that Will's code had fixed your issue. That's great. :)
Do you know if there is a way to directly load .obj-Files and resolve the
> references with own addresses? Like when somebody used printf in the
> generated obj-File, but I replace the address with my own printf?
You can load precompiled object files by calling addObjectSet on the
ObjectLayer.
All external symbol references are resolved by the JITSymbolResolver that
is created by createLambdaResolver. In your example the resolution process
is two-step: First the JIT searches its own function definitions to see if
there is a function called "printf" defined there (this is what the call to
CompileLayer.findSymbol does):
[&](const std::string &Name) {
printf("FLUSH :0\n");
if (auto Sym = CompileLayer.findSymbol(Name, false))
return Sym;
return JITSymbol(nullptr);
}
Then, if it doesn't find a definition there, it falls back to searching in
the current process (this is what
RTDyldMemoryManager::getSymbolAddressInProcess does):
[](const std::string &S) {
printf("PLUSH :0\n");
if (auto SymAddr =
RTDyldMemoryManager::getSymbolAddressInProcess(S))
return JITSymbol(SymAddr, JITSymbolFlags::Exported);
return JITSymbol(nullptr);
}
If, for example, you wanted to redirect calls to printf to your own custom
version (while resolving all other externals by the normal process) you
could change the second lambda like so:
[](const std::string &S) {
printf("PLUSH :0\n");
if (S == mangleName("printf"))
return JITSymbol((JITSymbolAddress)&myCustomPrintf,
JITSymbolFlags::Exported);
if (auto SymAddr =
RTDyldMemoryManager::getSymbolAddressInProcess(S))
return JITSymbol(SymAddr, JITSymbolFlags::Exported);
return JITSymbol(nullptr);
}
(You'll just have to pull the mangling logic from findSymbol out into its
own "mangleName" function for this).
Hope this helps.
Cheers,
Lang.
On Sun, Apr 23, 2017 at 11:08 PM, <bjoern.gaier at horiba.com> wrote:
> Hello Mr. Dietz,
>
> I tried using your code and now it works! I'm happy and surprised! I will
> now compare the codes and try to spot the main difference! Thanks for your
> help!
> Do you know if there is a way to directly load .obj-Files and resolve the
> references with own addresses? Like when somebody used printf in the
> generated obj-File, but I replace the address with my own printf?
>
> Kind regards
> Björn
>
>
>
> From: Will Dietz <willdtz at gmail.com>
> To: bjoern.gaier at horiba.com
> Cc: Lang Hames <lhames at gmail.com>, Clang Dev <
> cfe-dev at lists.llvm.org>
> Date: 21.04.2017 21:50
> Subject: Re: [cfe-dev] JIT doens't resolve address
> Sent by: w at wdtz.org
> ------------------------------
>
>
>
> Hmm, I tried using your code (copy+pasted and then mass-dumped headers to
> fix includes), and it seems to work fine for me:
>
>
> *https://gist.github.com/dtzWill/df84b64a73001532e3fcfe73a2cffbb9#file-test-log*
> <https://gist.github.com/dtzWill/df84b64a73001532e3fcfe73a2cffbb9#file-test-log>
>
> Do you get different results when using your LLVM? If not, can you
> identify the differences between your code and what I constructed from your
> snippets?
>
> I noticed "PAUSE", are you on Windows? I'm not sure what the
> functionality/status of the JIT on Windows is, perhaps someone else can
> comment on that.
>
> ~Will
>
> On Fri, Apr 21, 2017 at 1:03 AM, via cfe-dev <*cfe-dev at lists.llvm.org*
> <cfe-dev at lists.llvm.org>> wrote:
> Hello Lang,
>
> the Code for my jit_main is a normal printf-HelloWorld program. I opended
> the file with notepad and found the following:
> ; Function Attrs: noinline norecurse uwtable
> define i32 @main() #0 {
> entry:
> %retval = alloca i32, align 4
> store i32 0, i32* %retval, align 4
> %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([35 x
> i8], [35 x i8]* @"\01??_C at _0CD@CMJEAMCD at Planschbeckilein?5sagt?
> 5Halloilein@", i32 0, i32 0))
> %call1 = call i32 @system(i8* getelementptr inbounds ([6 x i8], [6 x
> i8]* @"\01??_C at _05DIAHPDGL@PAUSE?$AA@", i32 0, i32 0))
> ret i32 0
> }
>
>
> So... there is a main... Anyway! The code for the main is this one:
> #include <stdio.h>
> #include <stdlib.h>
>
> int main()
> {
> printf("Planschbeckilein sagt Halloilein!\n");
> system("PAUSE");
>
> return 0;
> }
>
>
> Kind regards
> Björn
>
>
>
> From: Lang Hames <*lhames at gmail.com* <lhames at gmail.com>>
> To: *bjoern.gaier at horiba.com* <bjoern.gaier at horiba.com>
> Cc: Clang Dev <*cfe-dev at lists.llvm.org* <cfe-dev at lists.llvm.org>>
> Date: 20.04.2017 22:54
> Subject: Re: [cfe-dev] JIT doens't resolve address
> ------------------------------
>
>
>
>
> Hi Bjoern,
>
> Sorry - I just noticed that the address for your "main" function has come
> back as '0'. In this case the answer is even simpler: The JIT never found
> the function at all, and so definitely didn't have any external symbols to
> resolve, so it never called the resolver.
>
> A failure to find main has three likely causes:
>
> (1) jit_main.ll does not define main,
> (2) jit_main.ll defines main with private/internal linkage (the JIT can't
> see private/internal symbols in general)
> (3) jit_main.ll defines main with external linkage, but a system mangling
> is applied (e.g. on MacOSX 'main' is mangled to '_main'). The mangler code
> in your findSymbol function *should* correct for this, but this may fail if
> the default data layout for your TargetMachine varies from the Module's
> DataLayout.
>
> Can you share the contents of your jit_main.ll Module?
>
> Cheers,
> Lang.
>
>
> On Thu, Apr 20, 2017 at 1:35 PM, Lang Hames <*lhames at gmail.com*
> <lhames at gmail.com>> wrote:
> HI Bjoern,
>
> There are two kinds of symbol lookup in the JIT:
>
> (1) You want to find a symbol defined JIT'd code. This is what
> "findSymbol" on the JIT class does.
>
> (2) The JIT wants to fix up a module that contains references to symbols
> defined elsewhere (either in your program, or in other JIT'd code). This is
> the SymbolResolver's job.
>
> So assuming your main function in main.ll is trivial, e.g.
>
> int main() {
> return 0;
> }
>
> then your findSymbol call will return the address of the JIT'd main
> without ever needing to look anything up in the resolver.
>
> If, on the other hand, your main function contains an external reference,
> e.g.
>
> int main() {
> printf("Hello, World!"); // Reference to externally defined function
> printf.
> return 0;
> }
>
> Then you'll receive a call back on your resolver looking for the address
> of printf.
>
> Hope this helps!
>
> Cheers,
> Lang.
>
> On Thu, Apr 20, 2017 at 6:43 AM, via cfe-dev <*cfe-dev at lists.llvm.org*
> <cfe-dev at lists.llvm.org>> wrote:
> Hello LLVM-World,
>
> I was following the "Building a JIT in LLVM"-Tutorial and tried to load a
> normal main. My code is the following:
> class Jitter
> {
> private:
> std::unique_ptr<TargetMachine> TM;
> const DataLayout DL;
> ObjectLinkingLayer<> ObjectLayer;
> IRCompileLayer<decltype(ObjectLayer)> CompileLayer;
>
> public:
> typedef decltype(CompileLayer)::ModuleSetHandleT ModuleHandle;
>
> Jitter() : TM(EngineBuilder().selectTarget()), DL(TM->
> createDataLayout()),
> CompileLayer(ObjectLayer, SimpleCompiler(*TM))
> {printf("!");
> llvm::sys::DynamicLibrary::LoadLibraryPermanently(nullptr);
> }
>
> TargetMachine &getTargetMachine() { return *TM; }
>
> ModuleHandle addModule(std::unique_ptr<Module> &&M) {
> // Build our symbol resolver:
> // Lambda 1: Look back into the JIT itself to find symbols that are
> part of
> // the same "logical dylib".
> // Lambda 2: Search for external symbols in the host process.
> auto Resolver = createLambdaResolver(
> [&](const std::string &Name)
> {
> printf("FLUSH :0\n");
>
> if (auto Sym = CompileLayer.findSymbol(Name, false))
> return Sym;
> return JITSymbol(nullptr);
> },
> [](const std::string &S)
> {
> printf("PLUSH :0\n");
>
> if (auto SymAddr =
> RTDyldMemoryManager::getSymbolAddressInProcess(S))
> return JITSymbol(SymAddr, JITSymbolFlags::Exported);
> return JITSymbol(nullptr);
> });
>
> // Build a singleton module set to hold our module.
> std::vector<std::unique_ptr<Module>> Ms;
> Ms.push_back(std::move(M));
>
> // Add the set to the JIT with the resolver we created above and a newly
> // created SectionMemoryManager.
> return CompileLayer.addModuleSet(std::move(Ms),
> make_unique<SectionMemoryManager>(),
> std::move(Resolver));
> }
>
> JITSymbol findSymbol(const std::string Name) {
> std::string MangledName;
> raw_string_ostream MangledNameStream(MangledName);
> Mangler::getNameWithPrefix(MangledNameStream, Name, DL);
> printf("Tzearch for: %s\n\n", MangledNameStream.str());
> return CompileLayer.findSymbol(MangledNameStream.str(), false);
> }
>
> void removeModule(ModuleHandle H) {
> CompileLayer.removeModuleSet(H);
> }
>
> };
>
>
>
> And calling from main with:
> int main()
> {
> llvm::InitializeNativeTarget();
> llvm::InitializeNativeTargetAsmPrinter();
> llvm::InitializeNativeTargetAsmParser();
>
> llvm::LLVMContext context;
> llvm::SMDiagnostic dia;
>
> std::unique_ptr<llvm::Module> M = llvm::parseIRFile("./jit_main.
> ll", dia, context);
> Jitter jit;
> printf("Wuff?");
> Jitter::ModuleHandle h = jit.addModule(std::move(M));
> printf("KNUFF!\n");
>
> printf("Kuchen! 0x%p\n", jit.findSymbol("main").getAddress());
>
> system("PAUSE");
> return 0;
> }
>
>
> The Code runs without a fail, but when the programm tries to resolve
> "main" the address is 0. The strange thing: the printf "FLUSH :0\n" and "PLUSH
> :0\n" are never called, so did the code never compiled? What I'm doing
> wrong?
>
> Kind regards
> Björn
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
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>
>
>
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode, Heiko
> Lampert, Takashi Nagano, Takeshi Fukushima.
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>
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789
> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode, Heiko
> Lampert, Takashi Nagano, Takeshi Fukushima.
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