diff mbox series

[v15,14/21] target/riscv: disallow probe accesses to shadow stack

Message ID 20241003183342.679249-15-debug@rivosinc.com
State New
Headers show
Series riscv support for control flow integrity extensions | expand

Commit Message

Deepak Gupta Oct. 3, 2024, 6:33 p.m. UTC
`check_zicbom_access` (`cbo.clean/flush/inval`) may probe shadow stack
memory and must always raise store/AMO access fault because it has store
semantics.

For non-shadow stack memory even though `cbo.clean/flush/inval` have
store semantics, it will not fault if read is allowed (probably to follow
`clflush` on x86). Although if read is not allowed, eventually
`probe_write` will do store page (or access) fault (if permissions don't
allow it).

cbo operations on shadow stack memory must always raise store access fault.
Thus extending `get_physical_address` to recieve `probe` parameter as well.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
 target/riscv/cpu_helper.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 5580f5f3f3..ab46f694b5 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -884,7 +884,7 @@  static int get_physical_address(CPURISCVState *env, hwaddr *physical,
                                 target_ulong *fault_pte_addr,
                                 int access_type, int mmu_idx,
                                 bool first_stage, bool two_stage,
-                                bool is_debug)
+                                bool is_debug, bool is_probe)
 {
     /*
      * NOTE: the env->pc value visible here will not be
@@ -1030,7 +1030,7 @@  restart:
             int vbase_ret = get_physical_address(env, &vbase, &vbase_prot,
                                                  base, NULL, MMU_DATA_LOAD,
                                                  MMUIdx_U, false, true,
-                                                 is_debug);
+                                                 is_debug, false);
 
             if (vbase_ret != TRANSLATE_SUCCESS) {
                 if (fault_pte_addr) {
@@ -1117,8 +1117,11 @@  restart:
         /* if bcfi enabled, PTE_W is not reserved and shadow stack page */
         if (cpu_get_bcfien(env) && first_stage) {
             sstack_page = true;
-            /* if ss index, read and write allowed. else only read allowed */
-            rwx = is_sstack_idx ? PTE_R | PTE_W : PTE_R;
+            /*
+             * if ss index, read and write allowed. else if not a probe
+             * then only read allowed
+             */
+            rwx = is_sstack_idx ? (PTE_R | PTE_W) : (is_probe ? rwx :  PTE_R);
             break;
         }
         return TRANSLATE_FAIL;
@@ -1327,13 +1330,13 @@  hwaddr riscv_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
     int mmu_idx = riscv_env_mmu_index(&cpu->env, false);
 
     if (get_physical_address(env, &phys_addr, &prot, addr, NULL, 0, mmu_idx,
-                             true, env->virt_enabled, true)) {
+                             true, env->virt_enabled, true, false)) {
         return -1;
     }
 
     if (env->virt_enabled) {
         if (get_physical_address(env, &phys_addr, &prot, phys_addr, NULL,
-                                 0, MMUIdx_U, false, true, true)) {
+                                 0, MMUIdx_U, false, true, true, false)) {
             return -1;
         }
     }
@@ -1447,7 +1450,7 @@  bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
         /* Two stage lookup */
         ret = get_physical_address(env, &pa, &prot, address,
                                    &env->guest_phys_fault_addr, access_type,
-                                   mmu_idx, true, true, false);
+                                   mmu_idx, true, true, false, probe);
 
         /*
          * A G-stage exception may be triggered during two state lookup.
@@ -1470,7 +1473,7 @@  bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
 
             ret = get_physical_address(env, &pa, &prot2, im_address, NULL,
                                        access_type, MMUIdx_U, false, true,
-                                       false);
+                                       false, probe);
 
             qemu_log_mask(CPU_LOG_MMU,
                           "%s 2nd-stage address=%" VADDR_PRIx
@@ -1507,7 +1510,8 @@  bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
     } else {
         /* Single stage lookup */
         ret = get_physical_address(env, &pa, &prot, address, NULL,
-                                   access_type, mmu_idx, true, false, false);
+                                   access_type, mmu_idx, true, false, false,
+                                   probe);
 
         qemu_log_mask(CPU_LOG_MMU,
                       "%s address=%" VADDR_PRIx " ret %d physical "