[btdmaster]

I think you could argue there is already some effort to do type safety at the ISA register level, with e.g. shadow stack or control flow integrity. Isn't that very similar to this, except targeting program state rather than external memory?

[nine_k]

Tagged memory was a thing, and is a thing again on some ARM machines. Check out Google Pixel 9.

[Joker_vD]

I mean, if the stacks grew upwards, that alone would nip 90% of buffer overflow attacks in the bud. Moving the return address from the activation frame into a separate stack would help as well, but I understand that having an activation frame to be a single piece of data (a current continuation's closure, essentially) can be quite convenient.

[musicale]

The PL/I stack growing up rather than down reduced potential impact of stack overflows in Multics (and PL/I already had better memory safety, with bounded strings, etc.) TFA's author would probably have appreciated the segmented memory architecture as well.

There is no reason why the C/C++ stack can't grow up rather than down. On paged hardware, both the stack and heap could (and probably should) grow up. "C's stack should grow up", one might say.

[ch_123]

HP-UX on PA-RISC had an upward-growing stack. In practice, various exploits were developed which adapted to the changed direction of the stack.

One source from a few mins of searching: https://phrack.org/issues/58/11

[dmitrygr]

In ARMv4/v5 (non-thumb-mode) stack is purely a convention that hardware does not enforce. Nobody forces you to use r13 as the stack pointer or to make the stack descending. You can prototype your approach trivially with small changes to gcc and linux kernel. As this is a standard architectural feature, qemu and the like will support emulating this. And it would run fine on real hardware too. I'd read the paper you publish based on this.

[axoltl]

For modern systems, stack buffer overflow bugs haven't been great to exploit for a while. You need at least a stack cookie leak and on Apple Silicon the return addresses are MACed so overwriting them is a fools errand (2^-16 chance of success).

Most exploitable memory corruption bugs are heap buffer overflows.

[saagarjha]

It’s still fairly easy to attack buffer overflows if the stack grows upward