target/riscv: Assert that the CSR numbers will be correct

The CSRs will always be between either CSR_MHPMCOUNTER3 and
CSR_MHPMCOUNTER31 or CSR_MHPMCOUNTER3H and CSR_MHPMCOUNTER31H.

So although ctr_index can't be negative, Coverity doesn't know this and
it isn't obvious to human readers either. Let's add an assert to ensure
that Coverity knows the values will be within range.

To simplify the code let's also change the RV32 adjustment.

Fixes: Coverity CID 1523910
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240108001328.280222-2-alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index d8f751a0ae17b1af6a054ed5624d2ec964cfc8ba..674ea075a4ddbb67874713e1c65a2ce49c1f45dd 100644 (file)
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -195,8 +195,11 @@ static RISCVException mctr(CPURISCVState *env, int csrno)
 
     if ((riscv_cpu_mxl(env) == MXL_RV32) && csrno >= CSR_MCYCLEH) {
         /* Offset for RV32 mhpmcounternh counters */
-        base_csrno += 0x80;
+        csrno -= 0x80;
     }
+
+    g_assert(csrno >= CSR_MHPMCOUNTER3 && csrno <= CSR_MHPMCOUNTER31);
+
     ctr_index = csrno - base_csrno;
     if ((BIT(ctr_index) & pmu_avail_ctrs >> 3) == 0) {
         /* The PMU is not enabled or counter is out of range */