Hi Wangnan, I've been authoring the BCC development, so I'll answer those specific questions. > > > Could you please give us further information about your clang rewriter? > I guess you need a new .so when injecting those code into kernel?
The rewriter runs all of its passes in a single process, creating no files on disk and having no external dependencies in terms of toolchain. 1. Entry point: bpf_module_create() - C API call to create module, can take filename or directly a c string with the full contents of the program 2. Convert contents into a clang memory buffer 3. Set up a clang driver::CompilerInvocation in the style of the clang interpreter example 4. Run a rewriter pass over the memory buffer file, annotating and/or doing BPF specific magic on the input source a. Open BPF maps with a call to bpf_create_map directly b. Convert references to map operations with the specific FD of the new map c. Convert arguments to bpf_probe_read calls as needed d. Collect the externed function names to avoid section() hack in the language 5. Re-run the CompilerInvocation on the modified sources 6. JIT the llvm::Module to bpf arch 7. Load the resulting in-memory ".o" to bpf_prog_load, keeping the FD alive in the compiler process 8. Attach the FD as necessary to perf events, socket, tc, etc. 9. goto 1 The above steps are captured in the BCC github repo in src/cc, with the clang specific bits inside of the frontends/clang subdirectory. > I'm not sure. Our target platform should be embedded devices like > smartphone. > Bringing full clang/llvm environment there is not acceptable. The artifact from the build process of BCC is a shared library, which has the clang/llvm .a embedded within them. It is not yet a single binary, but not unfeasible to make it so. The clang toolchain itself does not need to exist on the target. I have not attempted to cross-compile BCC to any architecture, currently x86_64 only. If you have more BCC specific questions not involving clang/llvm, perhaps you can ping Alexei/myself off of the llvm-dev list, in case this discussion is not relevant to them. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/