diff options
author | Jason Molenda <jmolenda@apple.com> | 2016-07-06 23:06:19 +0000 |
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committer | Jason Molenda <jmolenda@apple.com> | 2016-07-06 23:06:19 +0000 |
commit | 10c616e38b2d1b349f2fa28b9291dd2a86822b04 (patch) | |
tree | b8510f95ef99081934a0c5151f88e80a6ad7bbab /source/Symbol/FuncUnwinders.cpp | |
parent | 877868761d9e4bf756b0ed9c7d4a27666e055510 (diff) |
Enhance FuncUnwinders::GetUnwindPlanAtNonCallSite to detect when we
may be in a function that is non-ABI conformant, and the eh_frame
instructions correctly describe how to unwind out of this function,
but the assembly parsing / arch default unwind plans would be
incorrect.
This is to address a problem that Ravitheja Addepally reported in
http://reviews.llvm.org/D21221 - I wanted to try handling the problem
with this approach which I think may be more generally helpful,
Ravitheja tested it and said it solves the problem on Linux/FreeBSD.
Ravi has a test case in http://reviews.llvm.org/D21221 that will
be committed separately.
Thanks for all the help on this one, Ravi.
git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@274700 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'source/Symbol/FuncUnwinders.cpp')
-rw-r--r-- | source/Symbol/FuncUnwinders.cpp | 74 |
1 files changed, 70 insertions, 4 deletions
diff --git a/source/Symbol/FuncUnwinders.cpp b/source/Symbol/FuncUnwinders.cpp index e81c8cca7..2fa41b84c 100644 --- a/source/Symbol/FuncUnwinders.cpp +++ b/source/Symbol/FuncUnwinders.cpp @@ -22,6 +22,7 @@ #include "lldb/Target/Thread.h" #include "lldb/Target/Target.h" #include "lldb/Target/UnwindAssembly.h" +#include "lldb/Utility/RegisterNumber.h" using namespace lldb; using namespace lldb_private; @@ -228,16 +229,81 @@ FuncUnwinders::GetAssemblyUnwindPlan (Target &target, Thread &thread, int curren return m_unwind_plan_assembly_sp; } +// This method compares the pc unwind rule in the first row of two UnwindPlans. +// If they have the same way of getting the pc value (e.g. "CFA - 8" + "CFA is sp"), +// then it will return LazyBoolTrue. +LazyBool +FuncUnwinders::CompareUnwindPlansForIdenticalInitialPCLocation (Thread& thread, const UnwindPlanSP &a, const UnwindPlanSP &b) +{ + LazyBool plans_are_identical = eLazyBoolCalculate; + + RegisterNumber pc_reg (thread, eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC); + uint32_t pc_reg_lldb_regnum = pc_reg.GetAsKind (eRegisterKindLLDB); + + if (a.get() && b.get()) + { + UnwindPlan::RowSP a_first_row = a->GetRowAtIndex (0); + UnwindPlan::RowSP b_first_row = b->GetRowAtIndex (0); + + if (a_first_row.get() && b_first_row.get()) + { + UnwindPlan::Row::RegisterLocation a_pc_regloc; + UnwindPlan::Row::RegisterLocation b_pc_regloc; + + a_first_row->GetRegisterInfo (pc_reg_lldb_regnum, a_pc_regloc); + b_first_row->GetRegisterInfo (pc_reg_lldb_regnum, b_pc_regloc); + + plans_are_identical = eLazyBoolYes; + + if (a_first_row->GetCFAValue() != b_first_row->GetCFAValue()) + { + plans_are_identical = eLazyBoolNo; + } + if (a_pc_regloc != b_pc_regloc) + { + plans_are_identical = eLazyBoolNo; + } + } + } + return plans_are_identical; +} UnwindPlanSP FuncUnwinders::GetUnwindPlanAtNonCallSite (Target& target, Thread& thread, int current_offset) { - UnwindPlanSP non_call_site_unwindplan_sp = GetEHFrameAugmentedUnwindPlan (target, thread, current_offset); - if (non_call_site_unwindplan_sp.get() == nullptr) + UnwindPlanSP eh_frame_sp = GetEHFrameUnwindPlan (target, current_offset); + UnwindPlanSP arch_default_at_entry_sp = GetUnwindPlanArchitectureDefaultAtFunctionEntry (thread); + UnwindPlanSP arch_default_sp = GetUnwindPlanArchitectureDefault (thread); + UnwindPlanSP assembly_sp = GetAssemblyUnwindPlan (target, thread, current_offset); + + // This point of this code is to detect when a function is using a non-standard ABI, and the eh_frame + // correctly describes that alternate ABI. This is addressing a specific situation on x86_64 linux + // systems where one function in a library pushes a value on the stack and jumps to another function. + // So using an assembly instruction based unwind will not work when you're in the second function - + // the stack has been modified in a non-ABI way. But we have eh_frame that correctly describes how to + // unwind from this location. So we're looking to see if the initial pc register save location from + // the eh_frame is different from the assembly unwind, the arch default unwind, and the arch default at + // initial function entry. + // + // We may have eh_frame that describes the entire function -- or we may have eh_frame that only describes + // the unwind after the prologue has executed -- so we need to check both the arch default (once the prologue + // has executed) and the arch default at initial function entry. And we may be running on a target where + // we have only some of the assembly/arch default unwind plans available. + + if (CompareUnwindPlansForIdenticalInitialPCLocation (thread, eh_frame_sp, arch_default_at_entry_sp) == eLazyBoolNo + && CompareUnwindPlansForIdenticalInitialPCLocation (thread, eh_frame_sp, arch_default_sp) == eLazyBoolNo + && CompareUnwindPlansForIdenticalInitialPCLocation (thread, assembly_sp, arch_default_sp) == eLazyBoolNo) { - non_call_site_unwindplan_sp = GetAssemblyUnwindPlan (target, thread, current_offset); + return eh_frame_sp; } - return non_call_site_unwindplan_sp; + + UnwindPlanSP eh_frame_augmented_sp = GetEHFrameAugmentedUnwindPlan (target, thread, current_offset); + if (eh_frame_augmented_sp) + { + return eh_frame_augmented_sp; + } + + return assembly_sp; } UnwindPlanSP |