| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS -- |
| -- -- |
| -- S Y S T E M - S T A C K _ U S A G E -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 2004-2011, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNARL 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 3, 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. -- |
| -- -- |
| -- As a special exception under Section 7 of GPL version 3, you are granted -- |
| -- additional permissions described in the GCC Runtime Library Exception, -- |
| -- version 3.1, as published by the Free Software Foundation. -- |
| -- -- |
| -- You should have received a copy of the GNU General Public License and -- |
| -- a copy of the GCC Runtime Library Exception along with this program; -- |
| -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- GNARL was developed by the GNARL team at Florida State University. -- |
| -- Extensive contributions were provided by Ada Core Technologies, Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| with System; |
| with System.Storage_Elements; |
| with System.Address_To_Access_Conversions; |
| with Interfaces; |
| |
| package System.Stack_Usage is |
| pragma Preelaborate; |
| |
| package SSE renames System.Storage_Elements; |
| |
| subtype Stack_Address is SSE.Integer_Address; |
| -- Address on the stack |
| |
| function To_Stack_Address |
| (Value : System.Address) return Stack_Address |
| renames System.Storage_Elements.To_Integer; |
| |
| Task_Name_Length : constant := 32; |
| -- The maximum length of task name displayed. |
| -- ??? Consider merging this variable with Max_Task_Image_Length. |
| |
| type Task_Result is record |
| Task_Name : String (1 .. Task_Name_Length); |
| |
| Value : Natural; |
| -- Amount of stack used. The value is calculated on the basis of the |
| -- mechanism used by GNAT to allocate it, and it is NOT a precise value. |
| |
| Stack_Size : Natural; |
| -- Size of the stack |
| end record; |
| |
| type Result_Array_Type is array (Positive range <>) of Task_Result; |
| |
| type Stack_Analyzer is private; |
| -- Type of the stack analyzer tool. It is used to fill a portion of the |
| -- stack with Pattern, and to compute the stack used after some execution. |
| |
| -- Usage: |
| |
| -- A typical use of the package is something like: |
| |
| -- A : Stack_Analyzer; |
| |
| -- task T is |
| -- pragma Storage_Size (A_Storage_Size); |
| -- end T; |
| |
| -- [...] |
| |
| -- Bottom_Of_Stack : aliased Integer; |
| -- -- Bottom_Of_Stack'Address will be used as an approximation of |
| -- -- the bottom of stack. A good practise is to avoid allocating |
| -- -- other local variables on this stack, as it would degrade |
| -- -- the quality of this approximation. |
| |
| -- begin |
| -- Initialize_Analyzer (A, |
| -- "Task t", |
| -- A_Storage_Size, |
| -- 0, |
| -- A_Storage_Size - A_Guard, |
| -- To_Stack_Address (Bottom_Of_Stack'Address)); |
| -- Fill_Stack (A); |
| -- Some_User_Code; |
| -- Compute_Result (A); |
| -- Report_Result (A); |
| -- end T; |
| |
| -- Errors: |
| -- |
| -- We are instrumenting the code to measure the stack used by the user |
| -- code. This method has a number of systematic errors, but several methods |
| -- can be used to evaluate or reduce those errors. Here are those errors |
| -- and the strategy that we use to deal with them: |
| |
| -- Bottom offset: |
| |
| -- Description: The procedure used to fill the stack with a given |
| -- pattern will itself have a stack frame. The value of the stack |
| -- pointer in this procedure is, therefore, different from the value |
| -- before the call to the instrumentation procedure. |
| |
| -- Strategy: The user of this package should measure the bottom of stack |
| -- before the call to Fill_Stack and pass it in parameter. The impact |
| -- is very minor unless the stack used is very small, but in this case |
| -- you aren't very interested by the figure. |
| |
| -- Instrumentation threshold at writing: |
| |
| -- Description: The procedure used to fill the stack with a given |
| -- pattern will itself have a stack frame. Therefore, it will |
| -- fill the stack after this stack frame. This part of the stack will |
| -- appear as used in the final measure. |
| |
| -- Strategy: As the user passes the value of the bottom of stack to |
| -- the instrumentation to deal with the bottom offset error, and as |
| -- the instrumentation procedure knows where the pattern filling start |
| -- on the stack, the difference between the two values is the minimum |
| -- stack usage that the method can measure. If, when the results are |
| -- computed, the pattern zone has been left untouched, we conclude |
| -- that the stack usage is inferior to this minimum stack usage. |
| |
| -- Instrumentation threshold at reading: |
| |
| -- Description: The procedure used to read the stack at the end of the |
| -- execution clobbers the stack by allocating its stack frame. If this |
| -- stack frame is bigger than the total stack used by the user code at |
| -- this point, it will increase the measured stack size. |
| |
| -- Strategy: We could augment this stack frame and see if it changes the |
| -- measure. However, this error should be negligible. |
| |
| -- Pattern zone overflow: |
| |
| -- Description: The stack grows outer than the topmost bound of the |
| -- pattern zone. In that case, the topmost region modified in the |
| -- pattern is not the maximum value of the stack pointer during the |
| -- execution. |
| |
| -- Strategy: At the end of the execution, the difference between the |
| -- topmost memory region modified in the pattern zone and the |
| -- topmost bound of the pattern zone can be understood as the |
| -- biggest allocation that the method could have detect, provided |
| -- that there is no "Untouched allocated zone" error and no "Pattern |
| -- usage in user code" error. If no object in the user code is likely |
| -- to have this size, this is not likely to happen. |
| |
| -- Pattern usage in user code: |
| |
| -- Description: The pattern can be found in the object of the user code. |
| -- Therefore, the address space where this object has been allocated |
| -- will appear as untouched. |
| |
| -- Strategy: Choose a pattern that is uncommon. 16#0000_0000# is the |
| -- worst choice; 16#DEAD_BEEF# can be a good one. A good choice is an |
| -- address which is not a multiple of 2, and which is not in the |
| -- target address space. You can also change the pattern to see if it |
| -- changes the measure. Note that this error *very* rarely influence |
| -- the measure of the total stack usage: to have some influence, the |
| -- pattern has to be used in the object that has been allocated on the |
| -- topmost address of the used stack. |
| |
| -- Stack overflow: |
| |
| -- Description: The pattern zone does not fit on the stack. This may |
| -- lead to an erroneous execution. |
| |
| -- Strategy: Specify a storage size that is bigger than the size of the |
| -- pattern. 2 times bigger should be enough. |
| |
| -- Augmentation of the user stack frames: |
| |
| -- Description: The use of instrumentation object or procedure may |
| -- augment the stack frame of the caller. |
| |
| -- Strategy: Do *not* inline the instrumentation procedures. Do *not* |
| -- allocate the Stack_Analyzer object on the stack. |
| |
| -- Untouched allocated zone: |
| |
| -- Description: The user code may allocate objects that it will never |
| -- touch. In that case, the pattern will not be changed. |
| |
| -- Strategy: There are no way to detect this error. Fortunately, this |
| -- error is really rare, and it is most probably a bug in the user |
| -- code, e.g. some uninitialized variable. It is (most of the time) |
| -- harmless: it influences the measure only if the untouched allocated |
| -- zone happens to be located at the topmost value of the stack |
| -- pointer for the whole execution. |
| |
| procedure Initialize (Buffer_Size : Natural); |
| pragma Export (C, Initialize, "__gnat_stack_usage_initialize"); |
| -- Initializes the size of the buffer that stores the results. Only the |
| -- first Buffer_Size results are stored. Any results that do not fit in |
| -- this buffer will be displayed on the fly. |
| |
| procedure Fill_Stack (Analyzer : in out Stack_Analyzer); |
| -- Fill an area of the stack with the pattern Analyzer.Pattern. The size |
| -- of this area is Analyzer.Size. After the call to this procedure, |
| -- the memory will look like that: |
| -- |
| -- Stack growing |
| -- ----------------------------------------------------------------------> |
| -- |<--------------------->|<----------------------------------->| |
| -- | Stack frames to | Memory filled with Analyzer.Pattern | |
| -- | Fill_Stack | | |
| -- ^ | ^ |
| -- Analyzer.Stack_Base | Analyzer.Pattern_Limit |
| -- ^ |
| -- Analyzer.Pattern_Limit +/- Analyzer.Pattern_Size |
| -- |
| |
| procedure Initialize_Analyzer |
| (Analyzer : in out Stack_Analyzer; |
| Task_Name : String; |
| Stack_Size : Natural; |
| Stack_Base : Stack_Address; |
| Pattern_Size : Natural; |
| Pattern : Interfaces.Unsigned_32 := 16#DEAD_BEEF#); |
| -- Should be called before any use of a Stack_Analyzer, to initialize it. |
| -- Max_Pattern_Size is the size of the pattern zone, might be smaller than |
| -- the full stack size Stack_Size in order to take into account e.g. the |
| -- secondary stack and a guard against overflow. The actual size taken |
| -- will be readjusted with data already used at the time the stack is |
| -- actually filled. |
| |
| Is_Enabled : Boolean := False; |
| -- When this flag is true, then stack analysis is enabled |
| |
| procedure Compute_Result (Analyzer : in out Stack_Analyzer); |
| -- Read the pattern zone and deduce the stack usage. It should be called |
| -- from the same frame as Fill_Stack. If Analyzer.Probe is not null, an |
| -- array of Unsigned_32 with Analyzer.Probe elements is allocated on |
| -- Compute_Result's stack frame. Probe can be used to detect the error: |
| -- "instrumentation threshold at reading". See above. After the call |
| -- to this procedure, the memory will look like: |
| -- |
| -- Stack growing |
| -- -----------------------------------------------------------------------> |
| -- |<---------------------->|<-------------->|<--------->|<--------->| |
| -- | Stack frames | Array of | used | Memory | |
| -- | to Compute_Result | Analyzer.Probe | during | filled | |
| -- | | elements | the | with | |
| -- | | | execution | pattern | |
| -- | | | |
| -- |<----------------------------------------------------> | |
| -- Stack used ^ |
| -- Pattern_Limit |
| |
| procedure Report_Result (Analyzer : Stack_Analyzer); |
| -- Store the results of the computation in memory, at the address |
| -- corresponding to the symbol __gnat_stack_usage_results. This is not |
| -- done inside Compute_Result in order to use as less stack as possible |
| -- within a task. |
| |
| procedure Output_Results; |
| -- Print the results computed so far on the standard output. Should be |
| -- called when all tasks are dead. |
| |
| pragma Export (C, Output_Results, "__gnat_stack_usage_output_results"); |
| |
| private |
| |
| package Unsigned_32_Addr is |
| new System.Address_To_Access_Conversions (Interfaces.Unsigned_32); |
| |
| subtype Pattern_Type is Interfaces.Unsigned_32; |
| Bytes_Per_Pattern : constant := Pattern_Type'Object_Size / Storage_Unit; |
| |
| type Stack_Analyzer is record |
| Task_Name : String (1 .. Task_Name_Length); |
| -- Name of the task |
| |
| Stack_Base : Stack_Address; |
| -- Address of the base of the stack, as given by the caller of |
| -- Initialize_Analyzer. |
| |
| Stack_Size : Natural; |
| -- Entire size of the analyzed stack |
| |
| Pattern_Size : Natural; |
| -- Size of the pattern zone |
| |
| Pattern : Pattern_Type; |
| -- Pattern used to recognize untouched memory |
| |
| Pattern_Limit : Stack_Address; |
| -- Bound of the pattern area farthest to the base |
| |
| Topmost_Touched_Mark : Stack_Address; |
| -- Topmost address of the pattern area whose value it is pointing |
| -- at has been modified during execution. If the systematic error are |
| -- compensated, it is the topmost value of the stack pointer during |
| -- the execution. |
| |
| Pattern_Overlay_Address : System.Address; |
| -- Address of the stack abstraction object we overlay over a |
| -- task's real stack, typically a pattern-initialized array. |
| |
| Result_Id : Positive; |
| -- Id of the result. If less than value given to gnatbind -u corresponds |
| -- to the location in the result array of result for the current task. |
| end record; |
| |
| Environment_Task_Analyzer : Stack_Analyzer; |
| |
| Compute_Environment_Task : Boolean; |
| |
| type Result_Array_Ptr is access all Result_Array_Type; |
| |
| Result_Array : Result_Array_Ptr; |
| pragma Export (C, Result_Array, "__gnat_stack_usage_results"); |
| -- Exported in order to have an easy accessible symbol in when debugging |
| |
| Next_Id : Positive := 1; |
| -- Id of the next stack analyzer |
| |
| function Stack_Size |
| (SP_Low : Stack_Address; |
| SP_High : Stack_Address) return Natural; |
| pragma Inline (Stack_Size); |
| -- Return the size of a portion of stack delimited by SP_High and SP_Low |
| -- (), i.e. the difference between SP_High and SP_Low. The storage element |
| -- pointed by SP_Low is not included in the size. Inlined to reduce the |
| -- size of the stack used by the instrumentation code. |
| |
| end System.Stack_Usage; |
