Add Zicfiss extension from CFI extension, v0.4.0

1. Add EXT_ZICFISS for enable Zicfiss with zicfiss extension name.
2. Add new software exception with tval 3 for shadow stack.
3. Implement sspush_x1/sspush_x5/sspopchk_x1/sspopchk_x5/ssrdp/ssamoswap_w/ssamoswap_d.
4. Implement c_sspush_x1/c_sspopchk_x5 in c_lui.h which has same encoding.
5. Add new special access type ss_access in xlate_flags_t for checking special read/write permission in SS(Shadow Stack) page.
6. Add new ss_load/ss_store/ssamoswap to enable ss_access flag.
7. Check special pte(xwr=010) of SS page.

1 files changed, 26 insertions, 3 deletions

diff --git a/riscv/mmu.cc b/riscv/mmu.cc
index 1a0c830..8660b71 100644
--- a/riscv/mmu.cc
+++ b/riscv/mmu.cc
@@ -63,7 +63,7 @@ reg_t mmu_t::translate(mem_access_info_t access_info, reg_t len)
   reg_t mode = (reg_t) access_info.effective_priv;
 
   reg_t paddr = walk(access_info) | (addr & (PGSIZE-1));
-  if (!pmp_ok(paddr, len, type, mode))
+  if (!pmp_ok(paddr, len, access_info.flags.ss_access ? STORE : type, mode))
     throw_access_exception(virt, addr, type);
   return paddr;
 }
@@ -491,6 +491,15 @@ reg_t mmu_t::walk(mem_access_info_t access_info)
   reg_t page_mask = (reg_t(1) << PGSHIFT) - 1;
   reg_t satp = proc->get_state()->satp->readvirt(virt);
   vm_info vm = decode_vm_info(proc->get_const_xlen(), false, mode, satp);
+
+  bool ss_access = access_info.flags.ss_access;
+
+  if (ss_access) {
+    if (vm.levels == 0)
+      trap_store_access_fault(virt, addr, 0, 0);
+    type = STORE;
+  }
+
   if (vm.levels == 0)
     return s2xlate(addr, addr & ((reg_t(2) << (proc->xlen-1))-1), type, type, virt, hlvx, false) & ~page_mask; // zero-extend from xlen
 
@@ -516,6 +525,7 @@ reg_t mmu_t::walk(mem_access_info_t access_info)
     reg_t ppn = (pte & ~reg_t(PTE_ATTR)) >> PTE_PPN_SHIFT;
     bool pbmte = virt ? (proc->get_state()->henvcfg->read() & HENVCFG_PBMTE) : (proc->get_state()->menvcfg->read() & MENVCFG_PBMTE);
     bool hade = virt ? (proc->get_state()->henvcfg->read() & HENVCFG_ADUE) : (proc->get_state()->menvcfg->read() & MENVCFG_ADUE);
+    bool sse = virt ? (proc->get_state()->henvcfg->read() & HENVCFG_SSE) : (proc->get_state()->menvcfg->read() & MENVCFG_SSE);
 
     if (pte & PTE_RSVD) {
       break;
@@ -531,11 +541,24 @@ reg_t mmu_t::walk(mem_access_info_t access_info)
       base = ppn << PGSHIFT;
     } else if ((pte & PTE_U) ? s_mode && (type == FETCH || !sum) : !s_mode) {
       break;
-    } else if (!(pte & PTE_V) || (!(pte & PTE_R) && (pte & PTE_W))) {
+    } else if (!(pte & PTE_V) ||
+              (!(pte & PTE_R) && (pte & PTE_W) && ((!sse && !(pte & PTE_X)) || (pte & PTE_X)))) {
+      // invalid
+      // not shadow stack access xwr=110 or xwr=010 page cause page fault
+      // shadow stack access with PTE_X moved to following check
       break;
+    } else if ((!(pte & PTE_R) && (pte & PTE_W) && !(pte & PTE_X)) && (type == STORE && !ss_access)) {
+      // not shadow stack store and  xwr = 010 cause access-fault
+      throw trap_store_access_fault(virt, addr, 0, 0);
+    } else if ((!(pte & PTE_R) && (pte & PTE_W) && !(pte & PTE_X)) && type == FETCH) {
+      // fetch from shadow stack pages cause instruction access-fault
+      throw trap_instruction_access_fault(virt, addr, 0, 0);
+    } else if ((((pte & PTE_R) && (pte & PTE_W)) || (pte & PTE_X)) && ss_access) {
+      // shadow stack access cause store access fault if xwr!=010 and xwr!=001
+      throw trap_store_access_fault(virt, addr, 0, 0);
     } else if (type == FETCH || hlvx ? !(pte & PTE_X) :
                type == LOAD          ? !(pte & PTE_R) && !(mxr && (pte & PTE_X)) :
-                                       !((pte & PTE_R) && (pte & PTE_W))) {
+                                       !(pte & PTE_W)) {
       break;
     } else if ((ppn & ((reg_t(1) << ptshift) - 1)) != 0) {
       break;