elp state is recorded in *status on trap entry (less privilege to higher
privilege) and restored in elp from *status on trap exit (higher to less
privilege).
Additionally this patch introduces a forward cfi helper function to
determine if current privilege has forward cfi is enabled or not based on
*envcfg (for U, VU, S, VU, HS) or mseccfg csr (for M). For qemu-user, a
new field `ufcfien` is introduced which is by default set to false and
helper function returns value deposited in `ufcfien` for qemu-user.
Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Co-developed-by: Jim Shu <jim.shu@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
target/riscv/cpu.h | 1 +
target/riscv/cpu_helper.c | 54 +++++++++++++++++++++++++++++++++++++++
target/riscv/op_helper.c | 18 +++++++++++++
3 files changed, 73 insertions(+)
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index b2dc419ad0..a7c970e70c 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -531,6 +531,7 @@ void riscv_cpu_set_geilen(CPURISCVState *env, target_ulong geilen);
bool riscv_cpu_vector_enabled(CPURISCVState *env);
void riscv_cpu_set_virt_enabled(CPURISCVState *env, bool enable);
int riscv_env_mmu_index(CPURISCVState *env, bool ifetch);
+bool cpu_get_fcfien(CPURISCVState *env);
G_NORETURN void riscv_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
MMUAccessType access_type,
int mmu_idx, uintptr_t retaddr);
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 6709622dd3..5f38969aa6 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -33,6 +33,7 @@
#include "cpu_bits.h"
#include "debug.h"
#include "tcg/oversized-guest.h"
+#include "pmp.h"
int riscv_env_mmu_index(CPURISCVState *env, bool ifetch)
{
@@ -63,6 +64,33 @@ int riscv_env_mmu_index(CPURISCVState *env, bool ifetch)
#endif
}
+bool cpu_get_fcfien(CPURISCVState *env)
+{
+ /* no cfi extension, return false */
+ if (!env_archcpu(env)->cfg.ext_zicfilp) {
+ return false;
+ }
+
+ switch (env->priv) {
+ case PRV_U:
+ if (riscv_has_ext(env, RVS)) {
+ return env->senvcfg & SENVCFG_LPE;
+ }
+ return env->menvcfg & MENVCFG_LPE;
+#ifndef CONFIG_USER_ONLY
+ case PRV_S:
+ if (env->virt_enabled) {
+ return env->henvcfg & HENVCFG_LPE;
+ }
+ return env->menvcfg & MENVCFG_LPE;
+ case PRV_M:
+ return env->mseccfg & MSECCFG_MLPE;
+#endif
+ default:
+ g_assert_not_reached();
+ }
+}
+
void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
uint64_t *cs_base, uint32_t *pflags)
{
@@ -546,6 +574,15 @@ void riscv_cpu_swap_hypervisor_regs(CPURISCVState *env)
}
bool current_virt = env->virt_enabled;
+ /*
+ * If zicfilp extension available and henvcfg.LPE = 1,
+ * then apply SPELP mask on mstatus
+ */
+ if (env_archcpu(env)->cfg.ext_zicfilp &&
+ get_field(env->henvcfg, HENVCFG_LPE)) {
+ mstatus_mask |= SSTATUS_SPELP;
+ }
+
g_assert(riscv_has_ext(env, RVH));
if (current_virt) {
@@ -1754,6 +1791,11 @@ void riscv_cpu_do_interrupt(CPUState *cs)
if (env->priv <= PRV_S && cause < 64 &&
(((deleg >> cause) & 1) || s_injected || vs_injected)) {
/* handle the trap in S-mode */
+ /* save elp status */
+ if (cpu_get_fcfien(env)) {
+ env->mstatus = set_field(env->mstatus, MSTATUS_SPELP, env->elp);
+ }
+
if (riscv_has_ext(env, RVH)) {
uint64_t hdeleg = async ? env->hideleg : env->hedeleg;
@@ -1802,6 +1844,11 @@ void riscv_cpu_do_interrupt(CPUState *cs)
riscv_cpu_set_mode(env, PRV_S);
} else {
/* handle the trap in M-mode */
+ /* save elp status */
+ if (cpu_get_fcfien(env)) {
+ env->mstatus = set_field(env->mstatus, MSTATUS_MPELP, env->elp);
+ }
+
if (riscv_has_ext(env, RVH)) {
if (env->virt_enabled) {
riscv_cpu_swap_hypervisor_regs(env);
@@ -1833,6 +1880,13 @@ void riscv_cpu_do_interrupt(CPUState *cs)
riscv_cpu_set_mode(env, PRV_M);
}
+ /*
+ * Interrupt/exception/trap delivery is asynchronous event and as per
+ * zicfilp spec CPU should clear up the ELP state. No harm in clearing
+ * unconditionally.
+ */
+ env->elp = false;
+
/*
* NOTE: it is not necessary to yield load reservations here. It is only
* necessary for an SC from "another hart" to cause a load reservation
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 2baf5bc3ca..5848aaf437 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -313,6 +313,15 @@ target_ulong helper_sret(CPURISCVState *env)
riscv_cpu_set_mode(env, prev_priv);
+ /*
+ * If forward cfi enabled for new priv, restore elp status
+ * and clear spelp in mstatus
+ */
+ if (cpu_get_fcfien(env)) {
+ env->elp = get_field(env->mstatus, MSTATUS_SPELP);
+ }
+ env->mstatus = set_field(env->mstatus, MSTATUS_SPELP, 0);
+
return retpc;
}
@@ -357,6 +366,15 @@ target_ulong helper_mret(CPURISCVState *env)
riscv_cpu_set_virt_enabled(env, prev_virt);
}
+ /*
+ * If forward cfi enabled for new priv, restore elp status
+ * and clear mpelp in mstatus
+ */
+ if (cpu_get_fcfien(env)) {
+ env->elp = get_field(env->mstatus, MSTATUS_MPELP);
+ }
+ env->mstatus = set_field(env->mstatus, MSTATUS_MPELP, 0);
+
return retpc;
}
--
2.44.0