On Fri, Jun 24, 2011 at 11:51 PM, Thomas Klein <th.r.kl...@web.de> wrote: > > Hi > > This is a ping of (http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01226.html). > Repeating my request. > > I would like to have a stack check for threads with small amount of stack > space per thread. > (I'm using a ARM Cortex-M3 microcontroller with a stack size of a 1 KByte per > Thread.) > Each thread having its own limit address. > The thread scheduler can then calculate the limit and store this value inside > of a global variable. > The compiler may generate code to check the stack for overflow at function > entry. > In principal this can be done this way: > - push registers as usual > - figure out if one or two work registers, that can be used directly without > extra push > - if not enough registers found push required work registers to stack > - load limit address into first working register > - load value of limit address (into the same register) > - if stack pointer will go to extend the stack (e.g. for local variables) > load this size value too (here the second work register can be used) > - compare for overflow > - if overflow occur "call" stack_failure function > - pop work registers that are pushed before > - continue function prologue as usual e.g. extend stack pointer > > The ARM target has an option "-mapcs-stack-check" but this is more or less > not working. (implementation seems to be missing) > There are also architecture independent options like > "-fstack-check=generic", "-fstack-limit-symbol=current_stack_limit" or > "-fstack-limit-register=r6" > that can be used. > > The generic stack check is doing a probe at end of function prologue phase > (e.g by writing 12K ahead the current stack pointer position). > If this stack space is not available the probe may generates a fault. > This require that the CPU is having a MPU or a MMU. > For machines with small memory space an additional mechanism should be > available. > > The option "-fstack-check" can be extend by the switches "direct" and > "indirect" to emit compare code in function prologue. > If switch "direct" is given the address of "-fstack-limit-symbol" represents > the limit itself. > If switch "indirect" is given "-fstack-limit-symbol" is a kind of global > variable that needs be read before comparison. Thomas,
I think your are working on a very useful feature. I have ARM MCU applications running of out stack space and resulting strange behaviors silently. I'd like to try your patch and probably give further comments - Joey
