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diff --git a/c_user/stack_bounds_checker.rst b/c_user/stack_bounds_checker.rst index 0cf075b..b7a0ff1 100644 --- a/c_user/stack_bounds_checker.rst +++ b/c_user/stack_bounds_checker.rst @@ -1,16 +1,22 @@ +.. COMMENT: COPYRIGHT (c) 1988-2008. +.. COMMENT: On-Line Applications Research Corporation (OAR). +.. COMMENT: All rights reserved. + Stack Bounds Checker #################### +.. index:: stack + Introduction ============ -The stack bounds checker is an RTEMS support component that determines -if a task has overrun its run-time stack. The routines provided -by the stack bounds checker manager are: +The stack bounds checker is an RTEMS support component that determines if a +task has overrun its run-time stack. The routines provided by the stack bounds +checker manager are: -- ``rtems_stack_checker_is_blown`` - Has the Current Task Blown its Stack +- rtems_stack_checker_is_blown_ - Has the Current Task Blown its Stack -- ``rtems_stack_checker_report_usage`` - Report Task Stack Usage +- rtems_stack_checker_report_usage_ - Report Task Stack Usage Background ========== @@ -18,53 +24,52 @@ Background Task Stack ---------- -Each task in a system has a fixed size stack associated with it. This -stack is allocated when the task is created. As the task executes, the -stack is used to contain parameters, return addresses, saved registers, -and local variables. The amount of stack space required by a task -is dependent on the exact set of routines used. The peak stack usage -reflects the worst case of subroutine pushing information on the stack. -For example, if a subroutine allocates a local buffer of 1024 bytes, then -this data must be accounted for in the stack of every task that invokes that -routine. +Each task in a system has a fixed size stack associated with it. This stack is +allocated when the task is created. As the task executes, the stack is used to +contain parameters, return addresses, saved registers, and local variables. +The amount of stack space required by a task is dependent on the exact set of +routines used. The peak stack usage reflects the worst case of subroutine +pushing information on the stack. For example, if a subroutine allocates a +local buffer of 1024 bytes, then this data must be accounted for in the stack +of every task that invokes that routine. Recursive routines make calculating peak stack usage difficult, if not -impossible. Each call to the recursive routine consumes *n* bytes -of stack space. If the routine recursives 1000 times, then ``1000 * *n*`` bytes of stack space are required. +impossible. Each call to the recursive routine consumes *n* bytes of stack +space. If the routine recursives 1000 times, then ``1000 * n`` bytes of +stack space are required. Execution --------- -The stack bounds checker operates as a set of task extensions. At -task creation time, the task's stack is filled with a pattern to -indicate the stack is unused. As the task executes, it will overwrite -this pattern in memory. At each task switch, the stack bounds checker's -task switch extension is executed. This extension checks that: +The stack bounds checker operates as a set of task extensions. At task +creation time, the task's stack is filled with a pattern to indicate the stack +is unused. As the task executes, it will overwrite this pattern in memory. At +each task switch, the stack bounds checker's task switch extension is executed. +This extension checks that: -- the last ``n`` bytes of the task's stack have - not been overwritten. If this pattern has been damaged, it - indicates that at some point since this task was context - switch to the CPU, it has used too much stack space. +- the last ``n`` bytes of the task's stack have not been overwritten. If this + pattern has been damaged, it indicates that at some point since this task was + context switch to the CPU, it has used too much stack space. -- the current stack pointer of the task is not within - the address range allocated for use as the task's stack. +- the current stack pointer of the task is not within the address range + allocated for use as the task's stack. -If either of these conditions is detected, then a blown stack -error is reported using the ``printk`` routine. +If either of these conditions is detected, then a blown stack error is reported +using the ``printk`` routine. The number of bytes checked for an overwrite is processor family dependent. The minimum stack frame per subroutine call varies widely between processor -families. On CISC families like the Motorola MC68xxx and Intel ix86, all -that is needed is a return address. On more complex RISC processors, -the minimum stack frame per subroutine call may include space to save -a significant number of registers. - -Another processor dependent feature that must be taken into account by -the stack bounds checker is the direction that the stack grows. On some -processor families, the stack grows up or to higher addresses as the -task executes. On other families, it grows down to lower addresses. The -stack bounds checker implementation uses the stack description definitions -provided by every RTEMS port to get for this information. +families. On CISC families like the Motorola MC68xxx and Intel ix86, all that +is needed is a return address. On more complex RISC processors, the minimum +stack frame per subroutine call may include space to save a significant number +of registers. + +Another processor dependent feature that must be taken into account by the +stack bounds checker is the direction that the stack grows. On some processor +families, the stack grows up or to higher addresses as the task executes. On +other families, it grows down to lower addresses. The stack bounds checker +implementation uses the stack description definitions provided by every RTEMS +port to get for this information. Operations ========== @@ -72,14 +77,16 @@ Operations Initializing the Stack Bounds Checker ------------------------------------- -The stack checker is initialized automatically when its task -create extension runs for the first time. +The stack checker is initialized automatically when its task create extension +runs for the first time. + +The application must include the stack bounds checker extension set in its set +of Initial Extensions. This set of extensions is defined as +``STACK_CHECKER_EXTENSION``. If using ``<rtems/confdefs.h>`` for Configuration +Table generation, then all that is necessary is to define the macro +``CONFIGURE_STACK_CHECKER_ENABLED`` before including ``<rtems/confdefs.h>`` as +shown below: -The application must include the stack bounds checker extension set -in its set of Initial Extensions. This set of extensions is -defined as ``STACK_CHECKER_EXTENSION``. If using ``<rtems/confdefs.h>`` -for Configuration Table generation, then all that is necessary is -to define the macro ``CONFIGURE_STACK_CHECKER_ENABLED`` before including``<rtems/confdefs.h>`` as shown below: .. code:: c #define CONFIGURE_STACK_CHECKER_ENABLED @@ -89,20 +96,19 @@ to define the macro ``CONFIGURE_STACK_CHECKER_ENABLED`` before including``<rtems Checking for Blown Task Stack ----------------------------- -The application may check whether the stack pointer of currently -executing task is within proper bounds at any time by calling -the ``rtems_stack_checker_is_blown`` method. This -method return ``FALSE`` if the task is operating within its -stack bounds and has not damaged its pattern area. +The application may check whether the stack pointer of currently executing task +is within proper bounds at any time by calling the +``rtems_stack_checker_is_blown`` method. This method return ``FALSE`` if the +task is operating within its stack bounds and has not damaged its pattern area. Reporting Task Stack Usage -------------------------- -The application may dynamically report the stack usage for every task -in the system by calling the``rtems_stack_checker_report_usage`` routine. -This routine prints a table with the peak usage and stack size of -every task in the system. The following is an example of the -report generated: +The application may dynamically report the stack usage for every task in the +system by calling the ``rtems_stack_checker_report_usage`` routine. This +routine prints a table with the peak usage and stack size of every task in the +system. The following is an example of the report generated: + .. code:: c ID NAME LOW HIGH AVAILABLE USED @@ -112,38 +118,40 @@ report generated: 0x08010004 TA3 0x003e0c40 0x003e3047 9096 1104 0xffffffff INTR 0x003ecfc0 0x003effbf 12160 128 -Notice the last time. The task id is 0xffffffff and its name is "INTR". +Notice the last line. The task id is ``0xffffffff`` and its name is ``INTR``. This is not actually a task, it is the interrupt stack. When a Task Overflows the Stack ------------------------------- -When the stack bounds checker determines that a stack overflow has occurred, -it will attempt to print a message using ``printk`` identifying the -task and then shut the system down. If the stack overflow has caused -corruption, then it is possible that the message cannot be printed. +When the stack bounds checker determines that a stack overflow has occurred, it +will attempt to print a message using ``printk`` identifying the task and then +shut the system down. If the stack overflow has caused corruption, then it is +possible that the message cannot be printed. The following is an example of the output generated: + .. code:: c BLOWN STACK!!! Offending task(0x3eb360): id=0x08010002; name=0x54413120 stack covers range 0x003e5750 - 0x003e7b57 (9224 bytes) Damaged pattern begins at 0x003e5758 and is 128 bytes long -The above includes the task id and a pointer to the task control block as -well as enough information so one can look at the task's stack and -see what was happening. +The above includes the task id and a pointer to the task control block as well +as enough information so one can look at the task's stack and see what was +happening. Routines ======== -This section details the stack bounds checker's routines. -A subsection is dedicated to each of routines -and describes the calling sequence, related constants, usage, -and status codes. +This section details the stack bounds checker's routines. A subsection is +dedicated to each of routines and describes the calling sequence, related +constants, usage, and status codes. .. COMMENT: rtems_stack_checker_is_blown +.. _rtems_stack_checker_is_blown: + STACK_CHECKER_IS_BLOWN - Has Current Task Blown Its Stack --------------------------------------------------------- @@ -155,20 +163,27 @@ STACK_CHECKER_IS_BLOWN - Has Current Task Blown Its Stack **STATUS CODES:** -``TRUE`` - Stack is operating within its stack limits -``FALSE`` - Current stack pointer is outside allocated area +.. list-table:: + :class: rtems-table + + * - ``TRUE`` + - Stack is operating within its stack limits + * - ``FALSE`` + - Current stack pointer is outside allocated area **DESCRIPTION:** -This method is used to determine if the current stack pointer -of the currently executing task is within bounds. +This method is used to determine if the current stack pointer of the currently +executing task is within bounds. **NOTES:** -This method checks the current stack pointer against -the high and low addresses of the stack memory allocated when -the task was created and it looks for damage to the high water -mark pattern for the worst case usage of the task being called. +This method checks the current stack pointer against the high and low addresses +of the stack memory allocated when the task was created and it looks for damage +to the high water mark pattern for the worst case usage of the task being +called. + +.. _rtems_stack_checker_report_usage: STACK_CHECKER_REPORT_USAGE - Report Task Stack Usage ---------------------------------------------------- @@ -179,7 +194,9 @@ STACK_CHECKER_REPORT_USAGE - Report Task Stack Usage void rtems_stack_checker_report_usage( void ); -**STATUS CODES: NONE** +**STATUS CODES:** + +NONE **DESCRIPTION:** @@ -189,10 +206,3 @@ allocation of every task in the system. **NOTES:** NONE - -.. COMMENT: COPYRIGHT (c) 1988-2007. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - |