Re: [PATCH] target/ppc: fix unreachable code in do_ldst_quad()

[Víctor Colombo]

On 20/07/2022 10:57, Daniel Henrique Barboza wrote:
> Coverity reports that commit fc34e81acd51 ("target/ppc: add macros to
> check privilege level") turned the following code unreachable:
>
> if (!prefixed && !(ctx->insns_flags2 & PPC2_LSQ_ISA207)) {
>      /* lq and stq were privileged prior to V. 2.07 */
>      REQUIRE_SV(ctx);
>
> > > >      CID 1490757:  Control flow issues  (UNREACHABLE)
> > > >      This code cannot be reached: "if (ctx->le_mode) {
>      if (ctx->le_mode) {
>          gen_align_no_le(ctx);
>          return true;
>      }
> }
>
> This happens because the macro REQUIRE_SV(), in CONFIG_USER_MODE, will
> always result in a 'return true' statement.
>
> Fix it by using "#if !defined(CONFIG_USER_ONLY)" to fold the code that
> shouldn't be there if we're running in a non-privileged state. This is
> also how the REQUIRE_SV() macro is being used in
> storage-ctrl-impl.c.inc.
>
> Fixes: Coverity CID 1490757
> Fixes: fc34e81acd51 ("target/ppc: add macros to check privilege level")
> Cc: Matheus Ferst <matheus.ferst@eldorado.org.br>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>   target/ppc/translate/fixedpoint-impl.c.inc | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/target/ppc/translate/fixedpoint-impl.c.inc 
> b/target/ppc/translate/fixedpoint-impl.c.inc
> index db14d3bebc..4a32fac4f3 100644
> --- a/target/ppc/translate/fixedpoint-impl.c.inc
> +++ b/target/ppc/translate/fixedpoint-impl.c.inc
> @@ -82,10 +82,14 @@ static bool do_ldst_quad(DisasContext *ctx, arg_D *a, bool 
> store, bool prefixed)
>           /* lq and stq were privileged prior to V. 2.07 */
>           REQUIRE_SV(ctx);
>
> +#if !defined(CONFIG_USER_ONLY)
>           if (ctx->le_mode) {
>               gen_align_no_le(ctx);
>               return true;
>           }
> +#else
> +    qemu_build_not_reached();

nit: I think the indentation here is off by 1 level (missing 4 spaces)?

> +#endif
>       }
>
>       if (!store && unlikely(a->ra == a->rt)) {
> --
> 2.36.1
Reviewed-by: Víctor Colombo <victor.colombo@eldorado.org.br>

--
Víctor Cora Colombo
Instituto de Pesquisas ELDORADO
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