[lldb-dev] LLDB does not respect platform sysroot when loading core on Linux

[Eugene Birukov via lldb-dev]

Hello,

I would appreciate advise how to fix this correctly...

I have a core dump from somebody's RHEL Linux and I am trying to open it on my Ubuntu. I have all the shared libraries from the target sitting under my local directory. So, GDB happily opens the core after I issue "set sysroot /path/to/local/root", but LLDB release_60 fails to do it.

I follow instructions from Greg's Clayton mail http://lists.llvm.org/pipermail/lldb-dev/2016-January/009236.html :

(lldb) platform select --sysroot /path/to/remote/shared/libraries remote-linux
(lldb) <load core>

Under debugger, I see that LLDB successfully created Platform object with m_sdk_root set to my path and the Target uses it as its platform:


(gdb) p target_sp->m_platform_sp->m_sdk_sysroot

$42 = {

  m_string = 0x80e070 "/tmp/debugcore.3WyoW4/lib2"

}

But this value is not used when it comes to DynamicLoaderPOSIXDYLD::LoadAllCurrentModules.

(gdb) bt

#0  lldb_private::ModuleList::GetSharedModule (module_spec=..., module_sp=std::shared_ptr (empty) 0x0,

    module_search_paths_ptr=0x83ad60, old_module_sp_ptr=0x7fffffffbb50, did_create_ptr=0x7fffffffbb07,

    always_create=false) at /home/eugene/llvm/tools/lldb/source/Core/ModuleList.cpp:710

#1  0x00007fffedc2d130 in lldb_private::Platform::<lambda(const lldb_private::ModuleSpec&)>::operator()(const lldb_private::ModuleSpec &) const (__closure=0x8581b0, spec=...)

    at /home/eugene/llvm/tools/lldb/source/Target/Platform.cpp:234

#2  0x00007fffedc34ff2 in std::_Function_handler<lldb_private::Status(const lldb_private::ModuleSpec&), lldb_private::Platform::GetSharedModule(const lldb_private::ModuleSpec&, lldb_private::Process*, lldb::ModuleSP&, const lldb_private::FileSpecList*, lldb::ModuleSP*, bool*)::<lambda(const lldb_private::ModuleSpec&)> >::_M_invoke(const std::_Any_data &, const lldb_private::ModuleSpec &) (__functor=..., __args#0=...) at /usr/include/c++/5/functional:1857

#3  0x00007fffedc37978 in std::function<lldb_private::Status (lldb_private::ModuleSpec const&)>::operator()(lldb_private::ModuleSpec const&) const (this=0x7fffffffba80, __args#0=...) at /usr/include/c++/5/functional:2267

#4  0x00007fffedc3375a in lldb_private::Platform::GetRemoteSharedModule(lldb_private::ModuleSpec const&, lldb_private::Process*, std::shared_ptr<lldb_private::Module>&, std::function<lldb_private::Status (lldb_private::ModuleSpec const&)> const&, bool*) (this=0x839330, module_spec=..., process=0x84d310, module_sp=std::shared_ptr (empty) 0x0,

    module_resolver=..., did_create_ptr=0x7fffffffbb07)

    at /home/eugene/llvm/tools/lldb/source/Target/Platform.cpp:1628

#5  0x00007fffedc2d2cd in lldb_private::Platform::GetSharedModule (this=0x839330, module_spec=...,

    process=0x84d310, module_sp=std::shared_ptr (empty) 0x0, module_search_paths_ptr=0x83ad60,

    old_module_sp_ptr=0x7fffffffbb50, did_create_ptr=0x7fffffffbb07)

    at /home/eugene/llvm/tools/lldb/source/Target/Platform.cpp:240

#6  0x00007fffedc9957c in lldb_private::Target::GetSharedModule (this=0x846960, module_spec=..., error_ptr=0x0)

    at /home/eugene/llvm/tools/lldb/source/Target/Target.cpp:1952

#7  0x00007fffef8e0d11 in lldb_private::DynamicLoader::LoadModuleAtAddress (this=0x9a0a70, file=...,

    link_map_addr=139700267943784, base_addr=139700263510016, base_addr_is_offset=true)

    at /home/eugene/llvm/tools/lldb/source/Core/DynamicLoader.cpp:171

#8  0x00007fffedd8fb55 in DynamicLoaderPOSIXDYLD::LoadAllCurrentModules (this=0x9a0a70)

    at /home/eugene/llvm/tools/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp:537

#9  0x00007fffedd8de52 in DynamicLoaderPOSIXDYLD::DidAttach (this=0x9a0a70)

    at /home/eugene/llvm/tools/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp:171

#10 0x00007fffedc476d9 in lldb_private::Process::LoadCore (this=0x84d310)

    at /home/eugene/llvm/tools/lldb/source/Target/Process.cpp:2853

I simply do not see any reference to sysroot in the GetSharedModule() code. What is there - it is only scanning module_search_paths_ptr looking for file. This would not work because the scan ignores the directory part of the module: it takes the next path from the list and appends the file name. What I need instead - take m_sdk_sysroot from Platform and append the full module - including directory - to it.

Unfortunately, GetSharedModule() is a static method and does not have any clue what is current platform or current target. So, should I pass another argument down there with sysroot or what? I have correct platform object at frame 4.

Thanks,
Eugene


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