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


From: Alistair Francis
Subject: Re: [PULL v3 36/42] target/riscv: Remove the hardcoded MSTATUS_SD macro
Date: Fri, 21 May 2021 08:55:34 +1000

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.

So it should always be able to return true.

Alistair

>
> Bug, or false positive ?
>
> thanks
> -- PMM



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