forked from Imagelibrary/rtems
70810dcd89
that contains: * Removes remaining (now illegal) references to $(SRC) from a couple of Makefile.ams * Removes duplicate AC_CONFIG_SUBDIRS macro from c/configure.in * Moves ENABLE_LIBCDIR into RTEMS_PROG_C[C|XX]_FOR_TARGET (hides LIBCDIR from most configure scripts, i.e. LIBCDIR becomes less visible) * Adds RTEMS_PROG_C[C|XX]_FOR_TARGET and RTEMS_CANONICALIZE_TOOLS to libbsp/*/configure.ins (A minor bug in previous implementations, which only has an impact when switching to GNU/Cygnus canonicalization) * Cleans up several bogus comments. * Removes MKLIB * Switches the version number to 4.5.0 (for testing version number handling)
#
# $Id$
#
Introduction
============
This directory contains a stack bounds checker. It provides two
primary features:
+ check for stack overflow at each context switch
+ provides an educated guess at each task's stack usage
Enabling
========
Add the stack checker extension to the initial user extension set.
If using confdefs.h to build your configuration table, this is
as simple as adding -DSTACK_CHECK_ON to the gcc command line which
compiles the file defining the configuration table. In the RTEMS
test suites and samples, this is always init.c
Background
==========
The stack overflow check at context switch works by looking for
a 16 byte pattern at the logical end of the stack to be corrupted.
The "guesser" assumes that the entire stack was prefilled with a known
pattern and assumes that the pattern is still in place if the memory
has not been used as a stack.
Both of these can be fooled by pushing large holes onto the stack
and not writing to them... or (much more unlikely) writing the
magic patterns into memory.
This code has not been extensively tested. It is provided as a tool
for RTEMS users to catch the most common mistake in multitasking
systems ... too little stack space. Suggestions and comments are appreciated.
NOTES:
1. Stack usage information is questionable on CPUs which push
large holes on stack.
2. The stack checker has a tendency to generate a fault when
trying to print the helpful diagnostic message. If it comes
out, congratulations. If not, then the variable Stack_check_Blown_task
contains a pointer to the TCB of the offending task. This
is usually enough to go on.
FUTURE:
1. Determine how/if gcc will generate stack probe calls and support that.
2. Get accurate stack usage numbers on i960.. it pushes very large
holes on the stack.