[Qemu-devel] [PATCHv4 5/6] RISC-V: Fix a PMP bug where it succeeds even if PMP entry is off

[Hesham Almatary]

The current implementation returns 1 (PMP check success) if the address is in
range even if the PMP entry is off. This is a bug.

For example, if there is a PMP check in S-Mode which is in range, but its PMP
entry is off, this will succeed, which it should not.

The patch fixes this bug by only checking the PMP permissions if the address is
in range and its corresponding PMP entry it not off. Otherwise, it will keep
the ret = -1 which will be checked and handled correctly at the end of the
function.

Signed-off-by: Hesham Almatary <address@hidden>
Reviewed-by: Alistair Francis <address@hidden>
---
 target/riscv/pmp.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 89170bc11d..0a8e7a2dc4 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -259,11 +259,12 @@ bool pmp_hart_has_privs(CPURISCVState *env, target_ulong 
addr,
         /* fully inside */
         const uint8_t a_field =
             pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg);
-        if ((s + e) == 2) {
-            if (PMP_AMATCH_OFF == a_field) {
-                return 1;
-            }

+        /*
+         * If the PMP entry is not off and the address is in range, do the priv
+         * check
+         */
+        if (((s + e) == 2) && (PMP_AMATCH_OFF != a_field)) {
             allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
             if ((mode != PRV_M) || pmp_is_locked(env, i)) {
                 allowed_privs &= env->pmp_state.pmp[i].cfg_reg;
--
2.17.1