On Thu, Mar 6, 2025 at 4:47 PM Deepak Gupta <de...@rivosinc.com> wrote:
>
> Commit f06bfe3dc38c ("target/riscv: implement zicfiss instructions") adds
> `ssamoswap` instruction. `ssamoswap` takes the code-point from existing
> reserved encoding (and not a zimop like other shadow stack instructions).
> If shadow stack is not enabled (via xenvcfg.SSE) and effective priv is
> less than M then `ssamoswap` must result in an illegal instruction
> exception. However if effective priv is M, then `ssamoswap` results in
> store/AMO access fault. See Section "22.2.3. Shadow Stack Memory
> Protection" of priv spec.
>
> Fixes: f06bfe3dc38c ("target/riscv: implement zicfiss instructions")
>
> Reported-by: Ved Shanbhogue <v...@rivosinc.com>
> Signed-off-by: Deepak Gupta <de...@rivosinc.com>Reviewed-by: Alistair Francis <alistair.fran...@wdc.com> Alistair > --- > target/riscv/insn_trans/trans_rvzicfiss.c.inc | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/target/riscv/insn_trans/trans_rvzicfiss.c.inc > b/target/riscv/insn_trans/trans_rvzicfiss.c.inc > index e3ebc4977c..b0096adcd0 100644 > --- a/target/riscv/insn_trans/trans_rvzicfiss.c.inc > +++ b/target/riscv/insn_trans/trans_rvzicfiss.c.inc > @@ -15,6 +15,13 @@ > * You should have received a copy of the GNU General Public License along > with > * this program. If not, see <http://www.gnu.org/licenses/>. > */ > + > +#define REQUIRE_ZICFISS(ctx) do { \ > + if (!ctx->cfg_ptr->ext_zicfiss) { \ > + return false; \ > + } \ > +} while (0) > + > static bool trans_sspopchk(DisasContext *ctx, arg_sspopchk *a) > { > if (!ctx->bcfi_enabled) { > @@ -77,6 +84,11 @@ static bool trans_ssrdp(DisasContext *ctx, arg_ssrdp *a) > static bool trans_ssamoswap_w(DisasContext *ctx, arg_amoswap_w *a) > { > REQUIRE_A_OR_ZAAMO(ctx); > + REQUIRE_ZICFISS(ctx); > + if (ctx->priv == PRV_M) { > + generate_exception(ctx, RISCV_EXCP_STORE_AMO_ACCESS_FAULT); > + } > + > if (!ctx->bcfi_enabled) { > return false; > } > @@ -97,6 +109,11 @@ static bool trans_ssamoswap_d(DisasContext *ctx, > arg_amoswap_w *a) > { > REQUIRE_64BIT(ctx); > REQUIRE_A_OR_ZAAMO(ctx); > + REQUIRE_ZICFISS(ctx); > + if (ctx->priv == PRV_M) { > + generate_exception(ctx, RISCV_EXCP_STORE_AMO_ACCESS_FAULT); > + } > + > if (!ctx->bcfi_enabled) { > return false; > } > -- > 2.34.1 > >
