From: Alistair Francis <alistair23@gmail.com>

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>
---
 target/riscv/csr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index d8f751a0ae..674ea075a4 100644
--- 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 */
-- 
2.43.0