target/riscv: Use g_assert() for the predicate() NULL check

At present riscv_csrrw_check() checks the CSR predicate() against
NULL and throws RISCV_EXCP_ILLEGAL_INST if it is NULL. But this is
a pure software check, and has nothing to do with the emulation of
the hardware behavior, thus it is inappropriate to return illegal
instruction exception when software forgets to install the hook.

Change to use g_assert() instead.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Weiwei Li<liweiwei@iscas.ac.cn>
Message-ID: <20230228104035.1879882-4-bmeng@tinylab.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 4cc2c63..cfd7ffc 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -3786,11 +3786,6 @@ static inline RISCVException riscv_csrrw_check(CPURISCVState *env,
         return RISCV_EXCP_ILLEGAL_INST;
     }
 
-    /* check predicate */
-    if (!csr_ops[csrno].predicate) {
-        return RISCV_EXCP_ILLEGAL_INST;
-    }
-
     /* read / write check */
     if (write_mask && read_only) {
         return RISCV_EXCP_ILLEGAL_INST;
@@ -3803,6 +3798,7 @@ static inline RISCVException riscv_csrrw_check(CPURISCVState *env,
      * illegal instruction exception should be triggered instead of virtual
      * instruction exception. Hence this comes after the read / write check.
      */
+    g_assert(csr_ops[csrno].predicate != NULL);
     RISCVException ret = csr_ops[csrno].predicate(env, csrno);
     if (ret != RISCV_EXCP_NONE) {
         return ret;