[PATCH v4 10/16] target/riscv: tb flag for shadow stack instructions

[Deepak Gupta <debug@rivosinc.com>]

Shadow stack instructions can be decoded as zimop / zcmop or shadow stack
instructions depending on whether shadow stack are enabled at current
privilege. This requires a TB flag so that correct TB generation and correct
TB lookup happens. `DisasContext` gets a field indicating whether bcfi is
enabled or not.

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        | 2 ++
 target/riscv/cpu_helper.c | 4 ++++
 target/riscv/translate.c  | 4 ++++
 3 files changed, 10 insertions(+)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 5a57099d59..dcc3bc9d93 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -613,6 +613,8 @@ FIELD(TB_FLAGS, AXL, 26, 2)
 /* zicfilp needs a TB flag to track indirect branches */
 FIELD(TB_FLAGS, FCFI_ENABLED, 28, 1)
 FIELD(TB_FLAGS, FCFI_LP_EXPECTED, 29, 1)
+/* zicfiss needs a TB flag so that correct TB is located based on tb flags */
+FIELD(TB_FLAGS, BCFI_ENABLED, 30, 1)
 
 #ifdef TARGET_RISCV32
 #define riscv_cpu_mxl(env)  ((void)(env), MXL_RV32)
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 96571177ef..d3115da28d 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -170,6 +170,10 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
         flags = FIELD_DP32(flags, TB_FLAGS, FCFI_ENABLED, 1);
     }
 
+    if (cpu_get_bcfien(env)) {
+        flags = FIELD_DP32(flags, TB_FLAGS, BCFI_ENABLED, 1);
+    }
+
 #ifdef CONFIG_USER_ONLY
     fs = EXT_STATUS_DIRTY;
     vs = EXT_STATUS_DIRTY;
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index f1522e8b96..4ba42597c4 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -119,6 +119,8 @@ typedef struct DisasContext {
     /* zicfilp extension. fcfi_enabled, lp expected or not */
     bool fcfi_enabled;
     bool fcfi_lp_expected;
+    /* zicfiss extension, if shadow stack was enabled during TB gen */
+    bool bcfi_enabled;
 } DisasContext;
 
 static inline bool has_ext(DisasContext *ctx, uint32_t ext)
@@ -1241,6 +1243,8 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     ctx->pm_base_enabled = FIELD_EX32(tb_flags, TB_FLAGS, PM_BASE_ENABLED);
     ctx->ztso = cpu->cfg.ext_ztso;
     ctx->itrigger = FIELD_EX32(tb_flags, TB_FLAGS, ITRIGGER);
+    ctx->bcfi_enabled = cpu_get_bcfien(env) &&
+                        FIELD_EX32(tb_flags, TB_FLAGS, BCFI_ENABLED);
     ctx->fcfi_lp_expected = FIELD_EX32(tb_flags, TB_FLAGS, FCFI_LP_EXPECTED);
     ctx->fcfi_enabled = FIELD_EX32(tb_flags, TB_FLAGS, FCFI_ENABLED);
     ctx->zero = tcg_constant_tl(0);
-- 
2.44.0