From f0ee69f75d61dc5c2ad476536ef695a50b320a6e Mon Sep 17 00:00:00 2001 From: Stefan Granitz Date: Thu, 9 May 2019 16:40:57 +0000 Subject: [PATCH] [JITLoaderGDB] Set eTypeJIT for objects read from JIT descriptors Summary: First part of a fix for JITed code debugging. This has been a regression from 5.0 to 6.0 and it's is still reproducible on current master: https://bugs.llvm.org/show_bug.cgi?id=36209 The address of the breakpoint site is corrupt: the 0x4 value we end up with, looks like an offset on a zero base address. When we parse the ELF section headers from the JIT descriptor, the load address for the text section we find in `header.sh_addr` is correct. The bug manifests in `VMAddressProvider::GetVMRange(const ELFSectionHeader &)` (follow it from `ObjectFileELF::CreateSections()`). Here we think the object type was `eTypeObjectFile` and unleash some extra logic [1] which essentially overwrites the address with a zero value. The object type is deduced from the ELF header's `e_type` in `ObjectFileELF::CalculateType()`. It never returns `eTypeJIT`, because the ELF header has no representation for it [2]. Instead the in-memory ELF object states `ET_REL`, which leads to `eTypeObjectFile`. This is what we get from `lli` at least since 3.x. (Might it be better to write `ET_EXEC` on the JIT side instead? In fact, relocations were already applied at this point, so "Relocatable" is not quite exact.) So, this patch proposes to set `eTypeJIT` explicitly whenever we read from a JIT descriptor. In `ObjectFileELF::CreateSections()` we can then call `GetType()`, which returns the explicit value or otherwise falls back to `CalculateType()`. LLDB then sets the breakpoint successfully. Next step: debug info. ``` Process 1056 stopped * thread #1, name = 'lli', stop reason = breakpoint 1.2 frame #0: 0x00007ffff7ff7000 JIT(0x3ba2030)`jitbp() JIT(0x3ba2030)`jitbp: -> 0x7ffff7ff7000 <+0>: pushq %rbp 0x7ffff7ff7001 <+1>: movq %rsp, %rbp 0x7ffff7ff7004 <+4>: movabsq $0x7ffff7ff6000, %rdi ; imm = 0x7FFFF7FF6000 0x7ffff7ff700e <+14>: movabsq $0x7ffff6697e80, %rcx ; imm = 0x7FFFF6697E80 ``` [1] It was first introduced with https://reviews.llvm.org/D38142#change-lF6csxV8HdlL, which has also been the original breaking change. The code has changed a lot since then. [2] ELF object types: https://github.com/llvm/llvm-project/blob/2d2277f5/llvm/include/llvm/BinaryFormat/ELF.h#L110 Reviewers: labath, JDevlieghere, bkoropoff, clayborg, espindola, alexshap, stella.stamenova Reviewed By: labath, clayborg Subscribers: probinson, emaste, aprantl, arichardson, MaskRay, AlexDenisov, yurydelendik, lldb-commits Tags: #lldb Differential Revision: https://reviews.llvm.org/D61611 llvm-svn: 360354 --- lldb/lit/Breakpoint/Inputs/jitbp.cpp | 2 ++ lldb/lit/Breakpoint/jitbp_elf.test | 12 ++++++++++++ lldb/lit/helper/toolchain.py | 2 +- lldb/source/Plugins/JITLoader/GDB/JITLoaderGDB.cpp | 4 ++++ lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp | 2 +- 5 files changed, 20 insertions(+), 2 deletions(-) create mode 100644 lldb/lit/Breakpoint/Inputs/jitbp.cpp create mode 100644 lldb/lit/Breakpoint/jitbp_elf.test diff --git a/lldb/lit/Breakpoint/Inputs/jitbp.cpp b/lldb/lit/Breakpoint/Inputs/jitbp.cpp new file mode 100644 index 000000000000..447d9d66df84 --- /dev/null +++ b/lldb/lit/Breakpoint/Inputs/jitbp.cpp @@ -0,0 +1,2 @@ +int jitbp() { return 0; } +int main() { return jitbp(); } diff --git a/lldb/lit/Breakpoint/jitbp_elf.test b/lldb/lit/Breakpoint/jitbp_elf.test new file mode 100644 index 000000000000..6bf8eab6e6e9 --- /dev/null +++ b/lldb/lit/Breakpoint/jitbp_elf.test @@ -0,0 +1,12 @@ +# REQUIRES: target-x86_64 +# XFAIL: system-windows + +# RUN: %clang -g -S -emit-llvm --target=x86_64-unknown-unknown-elf -o %t.ll %p/Inputs/jitbp.cpp +# RUN: %lldb -b -o 'settings set plugin.jit-loader.gdb.enable on' -o 'b jitbp' -o 'run -jit-kind=mcjit %t.ll' lli | FileCheck %s + +# CHECK: Breakpoint 1: no locations (pending). +# CHECK: (lldb) run -jit-kind=mcjit {{.*}}/jitbp_elf.test.tmp.ll +# CHECK: 1 location added to breakpoint 1 +# CHECK: Process {{.*}} stopped +# CHECK: JIT(0x{{.*}})`jitbp: +# CHECK: Process {{.*}} launched: {{.*}} diff --git a/lldb/lit/helper/toolchain.py b/lldb/lit/helper/toolchain.py index 61dfd84535d7..08fb7fe89809 100644 --- a/lldb/lit/helper/toolchain.py +++ b/lldb/lit/helper/toolchain.py @@ -134,6 +134,6 @@ def use_support_substitutions(config): support_tools = ['yaml2obj', 'obj2yaml', 'llvm-pdbutil', 'llvm-mc', 'llvm-readobj', 'llvm-objdump', - 'llvm-objcopy'] + 'llvm-objcopy', 'lli'] additional_tool_dirs += [config.lldb_tools_dir, config.llvm_tools_dir] llvm_config.add_tool_substitutions(support_tools, additional_tool_dirs) diff --git a/lldb/source/Plugins/JITLoader/GDB/JITLoaderGDB.cpp b/lldb/source/Plugins/JITLoader/GDB/JITLoaderGDB.cpp index 4fbdd22b84b2..890d9f996be6 100644 --- a/lldb/source/Plugins/JITLoader/GDB/JITLoaderGDB.cpp +++ b/lldb/source/Plugins/JITLoader/GDB/JITLoaderGDB.cpp @@ -327,6 +327,10 @@ bool JITLoaderGDB::ReadJITDescriptorImpl(bool all_entries) { FileSpec(jit_name), symbolfile_addr, symbolfile_size); if (module_sp && module_sp->GetObjectFile()) { + // Object formats (like ELF) have no representation for a JIT type. + // We will get it wrong, if we deduce it from the header. + module_sp->GetObjectFile()->SetType(ObjectFile::eTypeJIT); + // load the symbol table right away module_sp->GetObjectFile()->GetSymtab(); diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp index d41d9722fa2c..ff499dbad8cf 100644 --- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp +++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp @@ -1865,7 +1865,7 @@ void ObjectFileELF::CreateSections(SectionList &unified_section_list) { return; m_sections_up = llvm::make_unique(); - VMAddressProvider address_provider(CalculateType()); + VMAddressProvider address_provider(GetType()); size_t LoadID = 0; for (const auto &EnumPHdr : llvm::enumerate(ProgramHeaders())) {