I'm assuming there's a history to it, but why does the stack grow downward?
It seems to me like buffer overflows would be a lot harder to exploit if the stack grew upward…
Why Does the Stack Grow Downward?
cpustack
cpustack
I'm assuming there's a history to it, but why does the stack grow downward?
It seems to me like buffer overflows would be a lot harder to exploit if the stack grew upward…
Best Answer
I believe it comes from the very early days of computing, when memory was very limited, and it was not wise to pre-allocate a large chunk of memory for exclusive use by the stack. So, by allocating heap memory from address zero upwards, and stack memory from the end of the memory downwards, you could have both the heap and the stack share the same area of memory.
If you needed a bit more heap, you could be careful with your stack usage; if you needed more stack, you could try to free some heap memory. The result was, of course, mostly, spectacular crashes, as the stack would occasionally overwrite the heap and vice versa.
Back in those days there were no interwebz, so there was no issue of buffer overrun exploitations. (Or at least to the extent that the interwebz existed, it was all within high security facilities of the united states department of defense, so the possibility of malicious data did not need to be given much thought.)
After that, with most architectures it was all a matter of maintaining compatibility with previous versions of the same architecture. That's why upside-down stacks are still with us today.