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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S Y S T E M . T R A C E B A C K -- -- (HP/UX Version) -- -- -- -- B o d y -- -- -- -- Copyright (C) 1999-2006, AdaCore -- -- Copyright (C) 2008, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 2, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with Ada.Unchecked_Conversion; package body System.Traceback is -- This package implements the backtracing facility by way of a dedicated -- HP library for stack unwinding described in the "Runtime Architecture -- Document". pragma Linker_Options ("/usr/lib/libcl.a"); -- The library basically offers services to fetch information about a -- "previous" frame based on information about a "current" one. type Current_Frame_Descriptor is record cur_fsz : Address; -- Frame size of current routine. cur_sp : Address; -- The current value of stack pointer. cur_rls : Address; -- PC-space of the caller. cur_rlo : Address; -- PC-offset of the caller. cur_dp : Address; -- Data Pointer of the current routine. top_rp : Address; -- Initial value of RP. top_mrp : Address; -- Initial value of MRP. top_sr0 : Address; -- Initial value of sr0. top_sr4 : Address; -- Initial value of sr4. top_r3 : Address; -- Initial value of gr3. cur_r19 : Address; -- GR19 value of the calling routine. top_r4 : Address; -- Initial value of gr4. dummy : Address; -- Reserved. out_rlo : Address; -- PC-offset of the caller after get_previous. end record; type Previous_Frame_Descriptor is record prev_fsz : Address; -- frame size of calling routine. prev_sp : Address; -- SP of calling routine. prev_rls : Address; -- PC_space of calling routine's caller. prev_rlo : Address; -- PC_offset of calling routine's caller. prev_dp : Address; -- DP of calling routine. udescr0 : Address; -- low word of calling routine's unwind desc. udescr1 : Address; -- high word of calling routine's unwind desc. ustart : Address; -- start of the unwind region. uend : Address; -- end of the unwind region. uw_index : Address; -- index into the unwind table. prev_r19 : Address; -- GR19 value of the caller's caller. top_r3 : Address; -- Caller's initial gr3. top_r4 : Address; -- Caller's initial gr4. end record; -- Provide useful shortcuts for the names subtype CFD is Current_Frame_Descriptor; subtype PFD is Previous_Frame_Descriptor; -- Frames with dynamic stack allocation are handled using the associated -- frame pointer, but HP compilers and GCC setup this pointer differently. -- HP compilers set it to point at the top (highest address) of the static -- part of the frame, whereas GCC sets it to point at the bottom of this -- region. We have to fake the unwinder to compensate for this difference, -- for which we'll need to access some subprograms unwind descriptors. type Bits_2_Value is mod 2 ** 2; for Bits_2_Value'Size use 2; type Bits_4_Value is mod 2 ** 4; for Bits_4_Value'Size use 4; type Bits_5_Value is mod 2 ** 5; for Bits_5_Value'Size use 5; type Bits_27_Value is mod 2 ** 27; for Bits_27_Value'Size use 27; type Unwind_Descriptor is record cannot_unwind : Boolean; mcode : Boolean; mcode_save_restore : Boolean; region_desc : Bits_2_Value; reserved0 : Boolean; entry_sr : Boolean; entry_fr : Bits_4_Value; entry_gr : Bits_5_Value; args_stored : Boolean; variable_frame : Boolean; separate_package_body : Boolean; frame_extension_mcode : Boolean; stack_overflow_check : Boolean; two_steps_sp_adjust : Boolean; sr4_export : Boolean; cxx_info : Boolean; cxx_try_catch : Boolean; sched_entry_seq : Boolean; reserved1 : Boolean; save_sp : Boolean; save_rp : Boolean; save_mrp : Boolean; save_r19 : Boolean; cleanups : Boolean; hpe_interrupt_marker : Boolean; hpux_interrupt_marker : Boolean; large_frame : Boolean; alloca_frame : Boolean; reserved2 : Boolean; frame_size : Bits_27_Value; end record; for Unwind_Descriptor'Size use 64; for Unwind_Descriptor use record cannot_unwind at 0 range 0 .. 0; mcode at 0 range 1 .. 1; mcode_save_restore at 0 range 2 .. 2; region_desc at 0 range 3 .. 4; reserved0 at 0 range 5 .. 5; entry_sr at 0 range 6 .. 6; entry_fr at 0 range 7 .. 10; entry_gr at 1 range 3 .. 7; args_stored at 2 range 0 .. 0; variable_frame at 2 range 1 .. 1; separate_package_body at 2 range 2 .. 2; frame_extension_mcode at 2 range 3 .. 3; stack_overflow_check at 2 range 4 .. 4; two_steps_sp_adjust at 2 range 5 .. 5; sr4_export at 2 range 6 .. 6; cxx_info at 2 range 7 .. 7; cxx_try_catch at 3 range 0 .. 0; sched_entry_seq at 3 range 1 .. 1; reserved1 at 3 range 2 .. 2; save_sp at 3 range 3 .. 3; save_rp at 3 range 4 .. 4; save_mrp at 3 range 5 .. 5; save_r19 at 3 range 6 .. 6; cleanups at 3 range 7 .. 7; hpe_interrupt_marker at 4 range 0 .. 0; hpux_interrupt_marker at 4 range 1 .. 1; large_frame at 4 range 2 .. 2; alloca_frame at 4 range 3 .. 3; reserved2 at 4 range 4 .. 4; frame_size at 4 range 5 .. 31; end record; subtype UWD is Unwind_Descriptor; type UWD_Ptr is access all UWD; function To_UWD_Access is new Ada.Unchecked_Conversion (Address, UWD_Ptr); -- The descriptor associated with a given code location is retrieved -- using functions imported from the HP library, requiring the definition -- of additional structures. type Unwind_Table_Region is record Table_Start : Address; Table_End : Address; end record; -- An Unwind Table region, which is a memory area containing Unwind -- Descriptors. subtype UWT is Unwind_Table_Region; -- The subprograms imported below are provided by the HP library function U_get_unwind_table return UWT; pragma Import (C, U_get_unwind_table, "U_get_unwind_table"); -- Get the unwind table region associated with the current executable. -- This function is actually documented as having an argument, but which -- is only used for the MPE/iX targets. function U_get_shLib_unwind_table (r19 : Address) return UWT; pragma Import (C, U_get_shLib_unwind_table, "U_get_shLib_unw_tbl"); -- Return the unwind table region associated with a possible shared -- library, as determined by the provided r19 value. function U_get_shLib_text_addr (r19 : Address) return Address; pragma Import (C, U_get_shLib_text_addr, "U_get_shLib_text_addr"); -- Return the address at which the code for a shared library begins, or -- -1 if the value provided for r19 does not identify shared library code. function U_get_unwind_entry (Pc : Address; Space : Address; Table_Start : Address; Table_End : Address) return Address; pragma Import (C, U_get_unwind_entry, "U_get_unwind_entry"); -- Given the bounds of an unwind table, return the address of the -- unwind descriptor associated with a code location/space. In the case -- of shared library code, the offset from the beginning of the library -- is expected as Pc. procedure U_init_frame_record (Frame : not null access CFD); pragma Import (C, U_init_frame_record, "U_init_frame_record"); procedure U_prep_frame_rec_for_unwind (Frame : not null access CFD); pragma Import (C, U_prep_frame_rec_for_unwind, "U_prep_frame_rec_for_unwind"); -- Fetch the description data of the frame in which these two procedures -- are called. function U_get_u_rlo (Cur : not null access CFD; Prev : not null access PFD) return Integer; pragma Import (C, U_get_u_rlo, "U_IS_STUB_OR_CALLX"); -- From a complete current frame with a return location possibly located -- into a linker generated stub, and basic information about the previous -- frame, place the first non stub return location into the current frame. -- Return -1 if something went wrong during the computation. function U_is_shared_pc (rlo : Address; r19 : Address) return Address; pragma Import (C, U_is_shared_pc, "U_is_shared_pc"); -- Return 0 if the provided return location does not correspond to code -- in a shared library, or something non null otherwise. function U_get_previous_frame_x (current_frame : not null access CFD; previous_frame : not null access PFD; previous_size : Integer) return Integer; pragma Import (C, U_get_previous_frame_x, "U_get_previous_frame_x"); -- Fetch the data describing the "previous" frame relatively to the -- "current" one. "previous_size" should be the size of the "previous" -- frame descriptor provided. -- -- The library provides a simpler interface without the size parameter -- but it is not usable when frames with dynamically allocated space are -- on the way. ------------------ -- C_Call_Chain -- ------------------ function C_Call_Chain (Traceback : System.Address; Max_Len : Natural) return Natural is Val : Natural; begin Call_Chain (Traceback, Max_Len, Val); return Val; end C_Call_Chain; ---------------- -- Call_Chain -- ---------------- procedure Call_Chain (Traceback : System.Address; Max_Len : Natural; Len : out Natural; Exclude_Min : System.Address := System.Null_Address; Exclude_Max : System.Address := System.Null_Address; Skip_Frames : Natural := 1) is type Tracebacks_Array is array (1 .. Max_Len) of System.Address; pragma Suppress_Initialization (Tracebacks_Array); -- The code location returned by the unwinder is a return location but -- what we need is a call point. Under HP-UX call instructions are 4 -- bytes long and the return point they specify is 4 bytes beyond the -- next instruction because of the delay slot. Call_Size : constant := 4; DSlot_Size : constant := 4; Rlo_Offset : constant := Call_Size + DSlot_Size; -- Moreover, the return point is passed via a register which two least -- significant bits specify a privilege level that we will have to mask. Priv_Mask : constant := 16#00000003#; Frame : aliased CFD; Code : System.Address; J : Natural := 1; Pop_Success : Boolean; Trace : Tracebacks_Array; for Trace'Address use Traceback; -- The backtracing process needs a set of subprograms : function UWD_For_RLO_Of (Frame : not null access CFD) return UWD_Ptr; -- Return an access to the unwind descriptor for the caller of -- a given frame, using only the provided return location. function UWD_For_Caller_Of (Frame : not null access CFD) return UWD_Ptr; -- Return an access to the unwind descriptor for the user code caller -- of a given frame, or null if the information is not available. function Pop_Frame (Frame : not null access CFD) return Boolean; -- Update the provided machine state structure so that it reflects -- the state one call frame "above" the initial one. -- -- Return True if the operation has been successful, False otherwise. -- Failure typically occurs when the top of the call stack has been -- reached. function Prepare_For_Unwind_Of (Frame : not null access CFD) return Boolean; -- Perform the necessary adaptations to the machine state before -- calling the unwinder. Currently used for the specific case of -- dynamically sized previous frames. -- -- Return True if everything went fine, or False otherwise. Program_UWT : constant UWT := U_get_unwind_table; --------------- -- Pop_Frame -- --------------- function Pop_Frame (Frame : not null access CFD) return Boolean is Up_Frame : aliased PFD; State_Ready : Boolean; begin -- Check/adapt the state before calling the unwinder and return -- if anything went wrong. State_Ready := Prepare_For_Unwind_Of (Frame); if not State_Ready then return False; end if; -- Now, safely call the unwinder and use the results if U_get_previous_frame_x (Frame, Up_Frame'Access, Up_Frame'Size) /= 0 then return False; end if; -- In case a stub is on the way, the usual previous return location -- (the one in prev_rlo) is the one in the stub and the "real" one -- is placed in the "current" record, so let's take this one into -- account. Frame.out_rlo := Frame.cur_rlo; Frame.cur_fsz := Up_Frame.prev_fsz; Frame.cur_sp := Up_Frame.prev_sp; Frame.cur_rls := Up_Frame.prev_rls; Frame.cur_rlo := Up_Frame.prev_rlo; Frame.cur_dp := Up_Frame.prev_dp; Frame.cur_r19 := Up_Frame.prev_r19; Frame.top_r3 := Up_Frame.top_r3; Frame.top_r4 := Up_Frame.top_r4; return True; end Pop_Frame; --------------------------------- -- Prepare_State_For_Unwind_Of -- --------------------------------- function Prepare_For_Unwind_Of (Frame : not null access CFD) return Boolean is Caller_UWD : UWD_Ptr; FP_Adjustment : Integer; begin -- No need to bother doing anything if the stack is already fully -- unwound. if Frame.cur_rlo = 0 then return False; end if; -- When ALLOCA_FRAME is set in an unwind descriptor, the unwinder -- uses the value provided in current.top_r3 or current.top_r4 as -- a frame pointer to compute the size of the frame. What decides -- between r3 or r4 is the unwind descriptor LARGE_FRAME bit, with -- r4 chosen if the bit is set. -- The size computed by the unwinder is STATIC_PART + (SP - FP), -- which is correct with HP's frame pointer convention, but not -- with GCC's one since we end up with the static part accounted -- for twice. -- We have to compute r4 when it is required because the unwinder -- has looked for it at a place where it was not if we went through -- GCC frames. -- The size of the static part of a frame can be found in the -- associated unwind descriptor. Caller_UWD := UWD_For_Caller_Of (Frame); -- If we cannot get it, we are unable to compute the potentially -- necessary adjustments. We'd better not try to go on then. if Caller_UWD = null then return False; end if; -- If the caller frame is a GCC one, r3 is its frame pointer and -- points to the bottom of the frame. The value to provide for r4 -- can then be computed directly from the one of r3, compensating -- for the static part of the frame. -- If the caller frame is an HP one, r3 is used to locate the -- previous frame marker, that is it also points to the bottom of -- the frame (this is why r3 cannot be used as the frame pointer in -- the HP sense for large frames). The value to provide for r4 can -- then also be computed from the one of r3 with the compensation -- for the static part of the frame. FP_Adjustment := Integer (Caller_UWD.frame_size * 8); Frame.top_r4 := Address (Integer (Frame.top_r3) + FP_Adjustment); return True; end Prepare_For_Unwind_Of; ----------------------- -- UWD_For_Caller_Of -- ----------------------- function UWD_For_Caller_Of (Frame : not null access CFD) return UWD_Ptr is UWD_Access : UWD_Ptr; begin -- First try the most direct path, using the return location data -- associated with the frame. UWD_Access := UWD_For_RLO_Of (Frame); if UWD_Access /= null then return UWD_Access; end if; -- If we did not get a result, we might face an in-stub return -- address. In this case U_get_previous_frame can tell us what the -- first not-in-stub return point is. We cannot call it directly, -- though, because we haven't computed the potentially necessary -- frame pointer adjustments, which might lead to SEGV in some -- circumstances. Instead, we directly call the libcl routine which -- is called by U_get_previous_frame and which only requires few -- information. Take care, however, that the information is provided -- in the "current" argument, so we need to work on a copy to avoid -- disturbing our caller. declare U_Current : aliased CFD := Frame.all; U_Previous : aliased PFD; begin U_Previous.prev_dp := U_Current.cur_dp; U_Previous.prev_rls := U_Current.cur_rls; U_Previous.prev_sp := U_Current.cur_sp - U_Current.cur_fsz; if U_get_u_rlo (U_Current'Access, U_Previous'Access) /= -1 then UWD_Access := UWD_For_RLO_Of (U_Current'Access); end if; end; return UWD_Access; end UWD_For_Caller_Of; -------------------- -- UWD_For_RLO_Of -- -------------------- function UWD_For_RLO_Of (Frame : not null access CFD) return UWD_Ptr is UWD_Address : Address; -- The addresses returned by the library point to full descriptors -- including the frame information bits but also the applicable PC -- range. We need to account for this. Frame_Info_Offset : constant := 8; begin -- First try to locate the descriptor in the program's unwind table UWD_Address := U_get_unwind_entry (Frame.cur_rlo, Frame.cur_rls, Program_UWT.Table_Start, Program_UWT.Table_End); -- If we did not get it, we might have a frame from code in a -- stub or shared library. For code in stub we would have to -- compute the first non-stub return location but this is not -- the role of this subprogram, so let's just try to see if we -- can get a result from the tables in shared libraries. if UWD_Address = -1 and then U_is_shared_pc (Frame.cur_rlo, Frame.cur_r19) /= 0 then declare Shlib_UWT : constant UWT := U_get_shLib_unwind_table (Frame.cur_r19); Shlib_Start : constant Address := U_get_shLib_text_addr (Frame.cur_r19); Rlo_Offset : constant Address := Frame.cur_rlo - Shlib_Start; begin UWD_Address := U_get_unwind_entry (Rlo_Offset, Frame.cur_rls, Shlib_UWT.Table_Start, Shlib_UWT.Table_End); end; end if; if UWD_Address /= -1 then return To_UWD_Access (UWD_Address + Frame_Info_Offset); else return null; end if; end UWD_For_RLO_Of; -- Start of processing for Call_Chain begin -- Fetch the state for this subprogram's frame and pop it so that we -- start with an initial out_rlo "here". U_init_frame_record (Frame'Access); Frame.top_sr0 := 0; Frame.top_sr4 := 0; U_prep_frame_rec_for_unwind (Frame'Access); Pop_Success := Pop_Frame (Frame'Access); -- Skip the requested number of frames for I in 1 .. Skip_Frames loop Pop_Success := Pop_Frame (Frame'Access); end loop; -- Loop popping frames and storing locations until either a problem -- occurs, or the top of the call chain is reached, or the provided -- array is full. loop -- We have to test some conditions against the return location -- as it is returned, so get it as is first. Code := Frame.out_rlo; exit when not Pop_Success or else Code = 0 or else J = Max_Len + 1; -- Compute the call point from the retrieved return location : -- Mask the privilege bits and account for the delta between the -- call site and the return point. Code := (Code and not Priv_Mask) - Rlo_Offset; if Code < Exclude_Min or else Code > Exclude_Max then Trace (J) := Code; J := J + 1; end if; Pop_Success := Pop_Frame (Frame'Access); end loop; Len := J - 1; end Call_Chain; end System.Traceback;
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