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, 31 insertions, 1 deletions

diff --git a/riscv/mmu.h b/riscv/mmu.h
index 4404e4c..b218bf6 100644
--- a/riscv/mmu.h
+++ b/riscv/mmu.h
@@ -42,9 +42,10 @@ struct xlate_flags_t {
   const bool forced_virt : 1 {false};
   const bool hlvx : 1 {false};
   const bool lr : 1 {false};
+  const bool ss_access : 1 {false};
 
   bool is_special_access() const {
-    return forced_virt || hlvx || lr;
+    return forced_virt || hlvx || lr || ss_access;
   }
 };
 
@@ -127,6 +128,14 @@ public:
     return load<T>(addr, {.forced_virt=true, .hlvx=true});
   }
 
+  // shadow stack load
+  template<typename T>
+  T ss_load(reg_t addr) {
+    if ((addr & (sizeof(T) - 1)) != 0)
+      throw trap_store_access_fault((proc) ? proc->state.v : false, addr, 0, 0);
+    return load<T>(addr, {.forced_virt=false, .hlvx=false, .lr=false, .ss_access=true});
+  }
+
   template<typename T>
   void ALWAYS_INLINE store(reg_t addr, T val, xlate_flags_t xlate_flags = {}) {
     reg_t vpn = addr >> PGSHIFT;
@@ -149,6 +158,14 @@ public:
     store(addr, val, {.forced_virt=true});
   }
 
+  // shadow stack store
+  template<typename T>
+  void ss_store(reg_t addr, T val) {
+    if ((addr & (sizeof(T) - 1)) != 0)
+      throw trap_store_access_fault((proc) ? proc->state.v : false, addr, 0, 0);
+    store<T>(addr, val, {.forced_virt=false, .hlvx=false, .lr=false, .ss_access=true});
+  }
+
   // AMO/Zicbom faults should be reported as store faults
   #define convert_load_traps_to_store_traps(BODY) \
     try { \
@@ -175,6 +192,19 @@ public:
     })
   }
 
+  // for shadow stack amoswap
+  template<typename T>
+  T ssamoswap(reg_t addr, reg_t value) {
+      bool forced_virt = false;
+      bool hlvx = false;
+      bool lr = false;
+      bool ss_access = true;
+      store_slow_path(addr, sizeof(T), nullptr, {forced_virt, hlvx, lr, ss_access}, false, true);
+      auto data = load<T>(addr, {forced_virt, hlvx, lr, ss_access});
+      store<T>(addr, value, {forced_virt, hlvx, lr, ss_access});
+      return data;
+  }
+
   template<typename T>
   T amo_compare_and_swap(reg_t addr, T comp, T swap) {
     convert_load_traps_to_store_traps({