On Thu, May 20, 2021 at 11:51 PM Peter Maydell <[email protected]> wrote: > > On Tue, 11 May 2021 at 11:21, Alistair Francis <[email protected]> > wrote: > > > > From: Hou Weiying <[email protected]> > > > > This commit adds support for ePMP v0.9.1. > > > > The ePMP spec can be found in: > > https://docs.google.com/document/d/1Mh_aiHYxemL0umN3GTTw8vsbmzHZ_nxZXgjgOUzbvc8 > > > > Signed-off-by: Hongzheng-Li <[email protected]> > > Signed-off-by: Hou Weiying <[email protected]> > > Signed-off-by: Myriad-Dreamin <[email protected]> > > Signed-off-by: Alistair Francis <[email protected]> > > Reviewed-by: Bin Meng <[email protected]> > > Message-id: > > fef23b885f9649a4d54e7c98b168bdec5d297bb1.1618812899.git.alistair.fran...@wdc.com > > [ Changes by AF: > > - Rebase on master > > - Update to latest spec > > - Use a switch case to handle ePMP MML permissions > > - Fix a few bugs > > ] > > Signed-off-by: Alistair Francis <[email protected]> > > Hi; this code confuses Coverity into thinking that the pmp_hart_has_privs() > function might read the value pointed to by 'allowed_privs' when > it is uninitialized (CID 1453108): > > > > @@ -294,13 +351,94 @@ bool pmp_hart_has_privs(CPURISCVState *env, > > target_ulong addr, > > pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg); > > > > /* > > - * If the PMP entry is not off and the address is in range, do the > > priv > > - * check > > + * Convert the PMP permissions to match the truth table in the > > + * ePMP spec. > > */ > > + const uint8_t epmp_operation = > > + ((env->pmp_state.pmp[i].cfg_reg & PMP_LOCK) >> 4) | > > + ((env->pmp_state.pmp[i].cfg_reg & PMP_READ) << 2) | > > + (env->pmp_state.pmp[i].cfg_reg & PMP_WRITE) | > > + ((env->pmp_state.pmp[i].cfg_reg & PMP_EXEC) >> 2); > > Here we construct a value which can only be in the range [0,15], > but we do it in a way that Coverity isn't clever enough to figure out... > > > + > > if (((s + e) == 2) && (PMP_AMATCH_OFF != a_field)) { > > - *allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC; > > - if ((mode != PRV_M) || pmp_is_locked(env, i)) { > > - *allowed_privs &= env->pmp_state.pmp[i].cfg_reg; > > + /* > > + * If the PMP entry is not off and the address is in range, > > + * do the priv check > > + */ > > + if (!MSECCFG_MML_ISSET(env)) { > > + /* > > + * If mseccfg.MML Bit is not set, do pmp priv check > > + * This will always apply to regular PMP. > > + */ > > + *allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC; > > + if ((mode != PRV_M) || pmp_is_locked(env, i)) { > > + *allowed_privs &= env->pmp_state.pmp[i].cfg_reg; > > + } > > + } else { > > + /* > > + * If mseccfg.MML Bit set, do the enhanced pmp priv check > > + */ > > + if (mode == PRV_M) { > > + switch (epmp_operation) { > > + case 0: > > + case 1: > > + case 4: > > + case 5: > > + case 6: > > + case 7: > > + case 8: > > + *allowed_privs = 0; > > + break; > > + case 2: > > + case 3: > > + case 14: > > + *allowed_privs = PMP_READ | PMP_WRITE; > > + break; > > + case 9: > > + case 10: > > + *allowed_privs = PMP_EXEC; > > + break; > > + case 11: > > + case 13: > > + *allowed_privs = PMP_READ | PMP_EXEC; > > + break; > > + case 12: > > + case 15: > > + *allowed_privs = PMP_READ; > > + break; > > ...so coverity thinks that "via the 'default' case" is a valid flow > of control in these switch() statements... > > > + } > > + } else { > > + switch (epmp_operation) { > > + case 0: > > + case 8: > > + case 9: > > + case 12: > > + case 13: > > + case 14: > > + *allowed_privs = 0; > > + break; > > + case 1: > > + case 10: > > + case 11: > > + *allowed_privs = PMP_EXEC; > > + break; > > + case 2: > > + case 4: > > + case 15: > > + *allowed_privs = PMP_READ; > > + break; > > + case 3: > > + case 6: > > + *allowed_privs = PMP_READ | PMP_WRITE; > > + break; > > + case 5: > > + *allowed_privs = PMP_READ | PMP_EXEC; > > + break; > > + case 7: > > + *allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC; > > + break; > > + } > > + } > > } > > > > ret = ((privs & *allowed_privs) == privs); > > ...and that we can get to here without having ever set *allowed_privs. > > > Adding > default: > g_assert_not_reached(); > > to both switches should clarify to both Coverity and human readers that > the cases in the switch are a complete enumeration of the possibilities.
Thanks Peter, I'll send a fix. Alistair > > thanks > -- PMM
