UnwindPlan.h   [plain text]

#ifndef liblldb_UnwindPlan_h
#define liblldb_UnwindPlan_h

#include "lldb/lldb-private.h"
#include "lldb/Core/AddressRange.h"
#include "lldb/Core/Stream.h"
#include "lldb/Core/ConstString.h"

#include <map>
#include <vector>

namespace lldb_private {

// The UnwindPlan object specifies how to unwind out of a function - where
// this function saves the caller's register values before modifying them
// (for non-volatile aka saved registers) and how to find this frame's
// Canonical Frame Address (CFA).

// Most commonly, registers are saved on the stack, offset some bytes from
// the Canonical Frame Address, or CFA, which is the starting address of
// this function's stack frame (the CFA is same as the eh_frame's CFA,
// whatever that may be on a given architecture).
// The CFA address for the stack frame does not change during
// the lifetime of the function.

// Internally, the UnwindPlan is structured as a vector of register locations
// organized by code address in the function, showing which registers have been
// saved at that point and where they are saved.  
// It can be thought of as the expanded table form of the DWARF CFI 
// encoded information.

// Other unwind information sources will be converted into UnwindPlans before
// being added to a FuncUnwinders object.  The unwind source may be 
// an eh_frame FDE, a DWARF debug_frame FDE, or assembly language based 
// prologue analysis.
// The UnwindPlan is the canonical form of this information that the unwinder
// code will use when walking the stack.

class UnwindPlan {
public:

    class Row {
    public:
        class RegisterLocation
        {
        public:
    
            enum RestoreType
                {
                    unspecified,        // not specified, we may be able to assume this 
                                        // is the same register. gcc doesn't specify all 
                                        // initial values so we really don't know...
                    undefined,          // reg is not available, e.g. volatile reg
                    same,               // reg is unchanged
                    atCFAPlusOffset,    // reg = deref(CFA + offset)
                    isCFAPlusOffset,    // reg = CFA + offset
                    inOtherRegister,    // reg = other reg
                    atDWARFExpression,  // reg = deref(eval(dwarf_expr))
                    isDWARFExpression   // reg = eval(dwarf_expr)
                };
    
            RegisterLocation() : 
                m_type(unspecified), 
                m_location() 
            {
            }
    
            bool
            operator == (const RegisterLocation& rhs) const;
    
            bool
            operator != (const RegisterLocation &rhs) const
            {
                return !(*this == rhs);
            }
            
            void 
            SetUnspecified()
            {
                m_type = unspecified;
            }

            void 
            SetUndefined()
            {
                m_type = undefined;
            }
    
            void 
            SetSame()
            {
                m_type = same;
            }
    
            bool 
            IsSame () const 
            { 
                return m_type == same; 
            }

            bool 
            IsUnspecified () const
            {
                return m_type == unspecified; 
            }

            bool 
            IsCFAPlusOffset () const
            {
                return m_type == isCFAPlusOffset; 
            }

            bool 
            IsAtCFAPlusOffset () const
            {
                return m_type == atCFAPlusOffset; 
            }

            bool
            IsInOtherRegister () const
            {
                return m_type == inOtherRegister; 
            }

            bool
            IsAtDWARFExpression () const
            {
                return m_type == atDWARFExpression; 
            }

            bool
            IsDWARFExpression () const
            { 
                return m_type == isDWARFExpression; 
            }

            void
            SetAtCFAPlusOffset (int32_t offset)
            {
                m_type = atCFAPlusOffset;
                m_location.offset = offset;
            }
    
            void
            SetIsCFAPlusOffset (int32_t offset)
            {
                m_type = isCFAPlusOffset;
                m_location.offset = offset;
            }
    
            void 
            SetInRegister (uint32_t reg_num)
            {
                m_type = inOtherRegister;
                m_location.reg_num = reg_num;
            }
    
            uint32_t
            GetRegisterNumber () const
            {
                if (m_type == inOtherRegister)
                    return m_location.reg_num; 
                return LLDB_INVALID_REGNUM;
            }

            RestoreType
            GetLocationType () const
            {
                return m_type; 
            }

            int32_t
            GetOffset () const
            {
                if (m_type == atCFAPlusOffset || m_type == isCFAPlusOffset)
                    return m_location.offset;
                return 0;
            }
            
            void
            GetDWARFExpr (const uint8_t **opcodes, uint16_t& len) const
            {
                if (m_type == atDWARFExpression || m_type == isDWARFExpression)
                {
                    *opcodes = m_location.expr.opcodes; 
                    len = m_location.expr.length; 
                }
                else
                {
                    *opcodes = NULL;
                    len = 0;
                }
            }

            void
            SetAtDWARFExpression (const uint8_t *opcodes, uint32_t len);
    
            void
            SetIsDWARFExpression (const uint8_t *opcodes, uint32_t len);

            const uint8_t *
            GetDWARFExpressionBytes () 
            {
                if (m_type == atDWARFExpression || m_type == isDWARFExpression)
                    return m_location.expr.opcodes; 
                return NULL;
            }

            int
            GetDWARFExpressionLength ()
            {
                if (m_type == atDWARFExpression || m_type == isDWARFExpression)
                    return m_location.expr.length; 
                return 0;
            }

            void
            Dump (Stream &s, 
                  const UnwindPlan* unwind_plan, 
                  const UnwindPlan::Row* row, 
                  Thread* thread, 
                  bool verbose) const;

        private:
            RestoreType m_type;            // How do we locate this register?
            union
            {
                // For m_type == atCFAPlusOffset or m_type == isCFAPlusOffset
                int32_t offset;
                // For m_type == inOtherRegister
                uint32_t reg_num; // The register number
                // For m_type == atDWARFExpression or m_type == isDWARFExpression
                struct {
                    const uint8_t *opcodes;
                    uint16_t length;
                } expr;
            } m_location;
        };
    
    public:
        Row ();
    
        bool
        GetRegisterInfo (uint32_t reg_num, RegisterLocation& register_location) const;
    
        void
        SetRegisterInfo (uint32_t reg_num, const RegisterLocation register_location);
    
        lldb::addr_t
        GetOffset() const
        {
            return m_offset;
        }

        void
        SetOffset(lldb::addr_t offset)
        {
            m_offset = offset;
        }

        void
        SlideOffset(lldb::addr_t offset)
        {
            m_offset += offset;
        }

        uint32_t
        GetCFARegister () const
        {
            return m_cfa_reg_num;
        }
        
        bool
        SetRegisterLocationToAtCFAPlusOffset (uint32_t reg_num, 
                                              int32_t offset, 
                                              bool can_replace);

        bool
        SetRegisterLocationToIsCFAPlusOffset (uint32_t reg_num, 
                                              int32_t offset, 
                                              bool can_replace);

        bool
        SetRegisterLocationToUndefined (uint32_t reg_num, 
                                        bool can_replace, 
                                        bool can_replace_only_if_unspecified);

        bool
        SetRegisterLocationToUnspecified (uint32_t reg_num, 
                                          bool can_replace);

        bool
        SetRegisterLocationToRegister (uint32_t reg_num, 
                                       uint32_t other_reg_num,
                                       bool can_replace);

        bool
        SetRegisterLocationToSame (uint32_t reg_num, 
                                   bool must_replace);



        void
        SetCFARegister (uint32_t reg_num);

        int32_t
        GetCFAOffset () const
        {
            return m_cfa_offset;
        }

        void
        SetCFAOffset (int32_t offset)
        {
            m_cfa_offset = offset;
        }
    
        // Return the number of registers we have locations for
        int
        GetRegisterCount () const
        {
            return m_register_locations.size();
        }

        void
        Clear ();

        void
        Dump (Stream& s, const UnwindPlan* unwind_plan, Thread* thread, lldb::addr_t base_addr) const;

        bool
        operator == (const Row &rhs) const
        {
            if (m_offset == rhs.m_offset && 
                m_cfa_reg_num != rhs.m_cfa_reg_num &&
                m_cfa_offset != rhs.m_cfa_offset)
                return m_register_locations == rhs.m_register_locations;
            return false;
        }

        bool
        operator != (const Row &rhs) const
        {
            if (m_offset != rhs.m_offset ||
                m_cfa_reg_num != rhs.m_cfa_reg_num ||
                m_cfa_offset != rhs.m_cfa_offset)
                return true;
            
            return m_register_locations != rhs.m_register_locations;
        }

    protected:
        typedef std::map<uint32_t, RegisterLocation> collection;
        lldb::addr_t m_offset;      // Offset into the function for this row
        uint32_t m_cfa_reg_num;     // The Call Frame Address register number
        int32_t  m_cfa_offset;      // The offset from the CFA for this row
        collection m_register_locations;

    }; // class Row

public:

    UnwindPlan (uint32_t reg_kind) : 
        m_row_list (), 
        m_plan_valid_address_range (), 
        m_register_kind (reg_kind), 
        m_source_name ()
    {
    }

    ~UnwindPlan ()
	{
	}

    void 
    Dump (Stream& s, Thread* thread, lldb::addr_t base_addr) const;

    void 
    AppendRow (const Row& row);

    // Returns a pointer to the best row for the given offset into the function's instructions.
    // If offset is -1 it indicates that the function start is unknown - the final row in the UnwindPlan is returned.
    // In practice, the UnwindPlan for a function with no known start address will be the architectural default
    // UnwindPlan which will only have one row.
    const Row*
    GetRowForFunctionOffset (int offset) const;

    uint32_t
    GetRegisterKind () const
    {
        return m_register_kind;
    }

    void
    SetRegisterKind (uint32_t kind)
    {
        m_register_kind = kind;
    }
    
    uint32_t
    GetInitialCFARegister () const
    {
        if (m_row_list.empty())
            return LLDB_INVALID_REGNUM;
        return m_row_list.front().GetCFARegister();
    }

    // This UnwindPlan may not be valid at every address of the function span.  
    // For instance, a FastUnwindPlan will not be valid at the prologue setup 
    // instructions - only in the body of the function.
    void
    SetPlanValidAddressRange (const AddressRange& range);

    const AddressRange &
    GetAddressRange () const
    {
        return m_plan_valid_address_range;
    }

    bool
    PlanValidAtAddress (Address addr);

    bool
    IsValidRowIndex (uint32_t idx) const;

    const UnwindPlan::Row&
    GetRowAtIndex (uint32_t idx) const;

    const UnwindPlan::Row&
    GetLastRow () const;

    lldb_private::ConstString
    GetSourceName () const;

    void
    SetSourceName (const char *);

    int
    GetRowCount () const;

    void
    Clear()
    {
        m_row_list.clear();
        m_plan_valid_address_range.Clear();
        m_register_kind = lldb::eRegisterKindDWARF;
        m_source_name.Clear();
    }

    const RegisterInfo *
    GetRegisterInfo (Thread* thread, uint32_t reg_num) const;

private:

    
    typedef std::vector<Row> collection;
    collection m_row_list;
    AddressRange m_plan_valid_address_range;
    uint32_t m_register_kind;   // The RegisterKind these register numbers are in terms of - will need to be
                                // translated to lldb native reg nums at unwind time
    lldb_private::ConstString m_source_name;  // for logging, where this UnwindPlan originated from
}; // class UnwindPlan

} // namespace lldb_private

#endif //liblldb_UnwindPlan_h