Re: [PULL v3 36/42] target/riscv: Remove the hardcoded MSTATUS_SD macro

[Alistair Francis]

On Fri, May 21, 2021 at 12:09 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:
>
>
> On 5/21/21 6:55 AM, Alistair Francis wrote:
> > On Thu, May 20, 2021 at 11:55 PM Peter Maydell <peter.maydell@linaro.org> 
> > wrote:
> >> On Tue, 11 May 2021 at 11:22, Alistair Francis <alistair.francis@wdc.com> 
> >> wrote:
> >>> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> >>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> >>> Message-id: 
> >>> fcc125d96da941b56c817c9dd6068dc36478fc53.1619234854.git.alistair.francis@wdc.com
> >>> ---
> >>>   target/riscv/cpu_bits.h  | 10 ----------
> >>>   target/riscv/csr.c       | 12 ++++++++++--
> >>>   target/riscv/translate.c | 19 +++++++++++++++++--
> >>>   3 files changed, 27 insertions(+), 14 deletions(-)
> >>> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> >>> index 26eccc5eb1..a596f80f20 100644
> >>> --- a/target/riscv/translate.c
> >>> +++ b/target/riscv/translate.c
> >>> @@ -78,6 +78,17 @@ static inline bool has_ext(DisasContext *ctx, uint32_t 
> >>> ext)
> >>>       return ctx->misa & ext;
> >>>   }
> >>>
> >>> +#ifdef TARGET_RISCV32
> >>> +# define is_32bit(ctx)  true
> >>> +#elif defined(CONFIG_USER_ONLY)
> >>> +# define is_32bit(ctx)  false
> >>> +#else
> >>> +static inline bool is_32bit(DisasContext *ctx)
> >>> +{
> >>> +    return (ctx->misa & RV32) == RV32;
> >>> +}
> >>> +#endif
> >> Hi; Coverity points out (CID 1453107) that this is_32bit() function
> >> can never return true for at least some build configs, because RV32
> >> is defined as ((target_ulong)1 << (TARGET_LONG_BITS - 2))
> >> but ctx->misa is a uint32_t field, which (if TARGET_LONG_BITS is
> >> 64) is not big enough for the RV32 bit.
> > This seems like a false positive as RV32 is defined as:
> >
> > ((target_ulong)1 << (TARGET_LONG_BITS - 2))
> >
> > while ctx->misa is a target_ulong.
>
> Although the misa in RISCVCPUState is target_ulong, the misa in
> DisasContext is uint32_t.
>
> I think we should  fix up the misa in DisasContext.

Good catch, I'll send a patch.

Alistair

>
> Zhiwei
>
> >
> > So it should always be able to return true.
> >
> > Alistair
> >
> >> Bug, or false positive ?
> >>
> >> thanks
> >> -- PMM