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[rtl] Deny no-match X access in M-Mode while MML=1

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In ePMP spec, it specifies as:

```
Executing code with Machine mode privileges is only possible from memory
regions with a matching Mmode-only rule or a locked Shared-Region rule
with executable privileges. Executing code from a region without a
matching rule or with a matching S/U-mode-only rule is denied.
```

This change provides that.

Signed-off-by: Canberk Topal <ctopal@lowrisc.org>
This commit is contained in:
Canberk Topal 2022-08-01 13:59:34 +01:00 • committed by Canberk Topal
parent e93452e502
commit e242ef07ad
2 changed files with 9 additions and 2 deletions
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2
dv/uvm/core_ibex/fcov/core_ibex_pmp_fcov_if.sv
View file

@ -416,6 +416,8 @@ interface core_ibex_pmp_fcov_if import ibex_pkg::*; #(
logic pmp_current_priv_req_err;
assign pmp_current_priv_req_err =
g_pmp.pmp_i.access_fault_check(csr_pmp_mseccfg.mmwp,
csr_pmp_mseccfg.mml,
g_pmp.pmp_i.pmp_req_type_i[PMP_D],
g_pmp.pmp_i.region_match_all[PMP_D],
cs_registers_i.priv_mode_id_o,
current_priv_perm_check);

9
rtl/ibex_pmp.sv
View file

@ -123,14 +123,17 @@ module ibex_pmp #(
// Access fault determination / prioritization
function automatic logic access_fault_check (logic csr_pmp_mseccfg_mmwp,
logic csr_pmp_mseccfg_mml,
ibex_pkg::pmp_req_e pmp_req_type,
logic [PMPNumRegions-1:0] match_all,
ibex_pkg::priv_lvl_e priv_mode,
logic [PMPNumRegions-1:0] final_perm_check);
// When MSECCFG.MMWP is set default deny always, otherwise allow for M-mode, deny for other
// modes
logic access_fail = csr_pmp_mseccfg_mmwp | (priv_mode != PRIV_LVL_M);
// modes. Also deny unmatched for M-mode whe MSECCFG.MML is set and request type is EXEC.
logic access_fail = csr_pmp_mseccfg_mmwp | (priv_mode != PRIV_LVL_M) |
(csr_pmp_mseccfg_mml && (pmp_req_type == PMP_ACC_EXEC));
// PMP entries are statically prioritized, from 0 to N-1
// The lowest-numbered PMP entry which matches an address determines accessibility
@ -222,6 +225,8 @@ module ibex_pmp #(
// Once the permission checks of the regions are done, decide if the access is
// denied by figuring out the matching region and its permission check.
assign pmp_req_err_o[c] = access_fault_check(csr_pmp_mseccfg_i.mmwp,
csr_pmp_mseccfg_i.mml,
pmp_req_type_i[c],
region_match_all[c],
priv_mode_i[c],
region_perm_check[c]);