Hi Richard,

On Sat, 2018-01-06 at 11:27 +0000, Richard W.M. Jones wrote:
> I noticed as a side effect of compiling GCC for riscv64 that RISC-V's
> GCC doesn't support -fstack-clash-protection.  Do you know what is
> involved to add it?  From a naive point of view I don't understand
> why this feature depends on architecture at all.

Sorry, I don't know the precise details on the gcc side. I believe it
is architecture dependent because it depends on the exact calling
conventions and how specific call instructions that manipulate the
stack. gcc wants the stack probes to be as efficient as possible. So it
only explicitly lowers the stack and inserts probes if absolutely
necessary. That is also why there were originally subtle issues around
no-return functions (because their calling conventions are different
and so gcc couldn't rely on the stack pointer already being lowered
and/or arguments having been pushed on it already).

Cheers,

Mark
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