On 2/7/23 06:36, Björn Töpel wrote:
+bool rvv_first_use_handler(struct pt_regs *regs) +{ + __user u32 *epc = (u32 *)regs->epc; + u32 tval = (u32)regs->badaddr; + + /* If V has been enabled then it is not the first-use trap */ + if (vstate_query(regs)) + return false; + /* Get the instruction */ + if (!tval) { + if (__get_user(tval, epc)) + return false; + } + /* Filter out non-V instructions */ + if (!insn_is_vector(tval)) + return false; + /* Sanity check. datap should be null by the time of the first-use trap */ + WARN_ON(current->thread.vstate.datap); + /* + * Now we sure that this is a V instruction. And it executes in the + * context where VS has been off. So, try to allocate the user's V + * context and resume execution. + */ + if (rvv_thread_zalloc()) { + force_sig(SIGKILL); + return true; + }Should the altstack size be taken into consideration, like x86 does in validate_sigaltstack() (see __xstate_request_perm()).
For a preexisting alternate stack ? Otherwise there is no "configuration" like x86 to cross-check against and V fault implies large'ish signal stack.
See below as well.
Related; Would it make sense to implement sigaltstack_size_valid() for riscv, analogous to x86?
Indeed we need to do that for the case where alt stack is being setup, *after* V fault-on-first use. But how to handle an existing alt stack which might not be big enough to handle V state ?
-Vineet
