Merge pull request #363 from stnolting/pmp_locking

Fix PMP locking

Author: stnolting

CHANGELOG.md

@@ -31,7 +31,8 @@ mimpid = 0x01040312 => 01.04.03.12 => Version 01.04.03.12 => v1.4.3.12
 
 
 | Date (*dd.mm.yyyy*) | Version | Comment |
-|:----------:|:-------:|:--------|
+|:-------------------:|:-------:|:--------|
+| 11.07.2022 | 1.7.3.8 | **physical memory protection(PMP)**: locking entry `i` in TOR mode will now also prevent write access to `pmpaddr(i-1)` (RISC-V compatibility); [#363](https://github.com/stnolting/neorv32/pull/363) |
 | 09.07.2022 | 1.7.3.7 | :bug: fixed **bootloader's** byte order when using the flash for application storage: :warning: was BIG-endian, is now also LITTLE-endian; [#362](https://github.com/stnolting/neorv32/pull/362) |
 | 08.07.2022 | 1.7.3.6 | :test_tube: added burst mode option to **XIP module** to accelerate consecutive flash read accesses; :warning: fixed XIP endianness: was BIG-endian and is now LITTLE-endian; [#361](https://github.com/stnolting/neorv32/pull/361) |
 | 08.07.2022 | 1.7.3.5 | Update "raw" executable generation options of makefile and image generator; [#360](https://github.com/stnolting/neorv32/pull/360) |

docs/datasheet/cpu.adoc

@@ -64,23 +64,18 @@ has been moved to a separate repository: https://github.com/stnolting/neorv32-ve
 :sectnums:
 ==== RISC-V Incompatibility Issues and Limitations
 
-This list shows the currently identified issues regarding full RISC-V-compatibility. Note that most
-of the cases listed below are "special cases" that should not occur in "normal" programs. However,
-some of these incompatibilities can be circumvented using software emulation (for example for
-handling unaligned memory accesses).
+This list shows the currently identified issues regarding full RISC-V-compatibility.
 
 .Read-Only "Read-Write" CSRs
 [IMPORTANT]
-The NEORV32 <<_misa>> and <<_mtval>> CSRs are _read-only_ - the RISC-V specs. declare
-these registers as _read/write_. Any machine-mode write access to them is ignored and will _not_
+The NEORV32 <<_misa>> and <<_mtval>> CSRs are _read-only_ - the RISC-V specs. declares
+these registers to be _read/write_. Any machine-mode write access to them is ignored and will _not_
 cause any exceptions or side-effects to maintain RISC-V compatibility.
 
-.Physical Memory Protection
+.Physical Memory Protection (PMP)
 [IMPORTANT]
 The RISC-V-compatible NEORV32 <<_machine_physical_memory_protection_csrs>> only implements the **TOR**
-(top of region) mode and only up to 16 PMP regions. Furthermore, the <<_pmpcfg>>'s _lock bits_ only lock
-the according PMP entry and not the entries below. All region rules are checked in parallel **without**
-prioritization so for identical memory regions the most restrictive PMP rule will be enforced.
+(top of region) mode and only up to 16 PMP regions.
 
 .No Hardware Support of Misaligned Memory Accesses
 [WARNING]

docs/datasheet/cpu_csr.adoc

@@ -539,7 +539,8 @@ as the MSB is hardwired to zero
 |=======================
 
 [WARNING]
-Setting the lock bit `L` **only locks the according PMP entry** and not the PMP entries below!
+Setting the lock bit `L` and setting TOR mode in `pmpcfg(i)` will also lock write access to `pmpaddr(i-1)`.
+See the RISC-V specs. for more information.
 
 
 :sectnums!:

rtl/core/neorv32_cpu_control.vhd

@@ -1872,30 +1872,37 @@ begin
 
           -- physical memory protection --
           -- --------------------------------------------------------------------
-          -- R/W: pmpcfg* - PMP configuration registers --
-          if (csr.addr(11 downto 2) = csr_class_pmpcfg_c) then -- pmp configuration CSR class
-            for i in 0 to PMP_NUM_REGIONS-1 loop
-              if (csr.addr(1 downto 0) = std_ulogic_vector(to_unsigned(i/4, 2))) then
-                if (csr.pmpcfg(i)(7) = '0') then -- unlocked pmpcfg entry
-                  csr.pmpcfg(i)(0) <= csr.wdata((i mod 4)*8+0); -- R - read
-                  csr.pmpcfg(i)(1) <= csr.wdata((i mod 4)*8+1); -- W - write
-                  csr.pmpcfg(i)(2) <= csr.wdata((i mod 4)*8+2); -- X - execute
-                  csr.pmpcfg(i)(3) <= csr.wdata((i mod 4)*8+3); -- A_L - mode low [TOR-mode only!]
-                  csr.pmpcfg(i)(4) <= '0'; -- A_H - mode high [TOR-mode only!]
-                  csr.pmpcfg(i)(5) <= '0'; -- reserved
-                  csr.pmpcfg(i)(6) <= '0'; -- reserved
-                  csr.pmpcfg(i)(7) <= csr.wdata((i mod 4)*8+7); -- L (locked / also enforce in machine-mode)
+          if (PMP_NUM_REGIONS > 0) then
+            -- R/W: pmpcfg* - PMP configuration registers --
+            if (csr.addr(11 downto 2) = csr_class_pmpcfg_c) then -- pmp configuration CSR class
+              for i in 0 to PMP_NUM_REGIONS-1 loop
+                if (csr.addr(1 downto 0) = std_ulogic_vector(to_unsigned(i/4, 2))) then
+                  if (csr.pmpcfg(i)(7) = '0') then -- unlocked pmpcfg entry
+                    csr.pmpcfg(i)(0) <= csr.wdata((i mod 4)*8+0); -- R - read
+                    csr.pmpcfg(i)(1) <= csr.wdata((i mod 4)*8+1); -- W - write
+                    csr.pmpcfg(i)(2) <= csr.wdata((i mod 4)*8+2); -- X - execute
+                    csr.pmpcfg(i)(3) <= csr.wdata((i mod 4)*8+3); -- A_L - mode low [TOR-mode only!]
+                    csr.pmpcfg(i)(4) <= '0'; -- A_H - mode high [TOR-mode only!]
+                    csr.pmpcfg(i)(5) <= '0'; -- reserved
+                    csr.pmpcfg(i)(6) <= '0'; -- reserved
+                    csr.pmpcfg(i)(7) <= csr.wdata((i mod 4)*8+7); -- L (locked / also enforce in machine-mode)
+                  end if;
                 end if;
+              end loop; -- i (pmpcfg entry)
+            end if;
+            -- R/W: pmpaddr* - PMP address registers --
+            if (csr.addr(11 downto 4) = csr_class_pmpaddr_c) then
+              for i in 0 to PMP_NUM_REGIONS-2 loop
+                if (csr.addr(3 downto 0) = std_ulogic_vector(to_unsigned(i, 4))) and (csr.pmpcfg(i)(7) = '0') and -- unlocked access
+                  ((csr.pmpcfg(i+1)(7) = '0') or (csr.pmpcfg(i+1)(3) = '0')) then -- pmpcfg(i+1) not "LOCKED TOR" [TOR-mode only!]
+                  csr.pmpaddr(i) <= csr.wdata(data_width_c-3 downto index_size_f(PMP_MIN_GRANULARITY)-2);
+                end if;
+              end loop; -- i (PMP regions)
+              -- very last entry --
+              if (csr.addr(3 downto 0) = std_ulogic_vector(to_unsigned(PMP_NUM_REGIONS-1, 4))) and (csr.pmpcfg(PMP_NUM_REGIONS-1)(7) = '0') then -- unlocked access
+                csr.pmpaddr(PMP_NUM_REGIONS-1) <= csr.wdata(data_width_c-3 downto index_size_f(PMP_MIN_GRANULARITY)-2);
               end if;
-            end loop; -- i (pmpcfg entry)
-          end if;
-          -- R/W: pmpaddr* - PMP address registers --
-          if (csr.addr(11 downto 4) = csr_class_pmpaddr_c) then 
-            for i in 0 to PMP_NUM_REGIONS-1 loop
-              if (csr.addr(3 downto 0) = std_ulogic_vector(to_unsigned(i, 4))) and (csr.pmpcfg(i)(7) = '0') then -- unlocked pmpaddr access
-                csr.pmpaddr(i) <= csr.wdata(data_width_c-3 downto index_size_f(PMP_MIN_GRANULARITY)-2);
-              end if;
-            end loop; -- i (PMP regions)
+            end if;
           end if;
 
           -- machine counter setup --

rtl/core/neorv32_package.vhd

@@ -68,7 +68,7 @@ package neorv32_package is
   -- Architecture Constants (do not modify!) ------------------------------------------------
   -- -------------------------------------------------------------------------------------------
   constant data_width_c : natural := 32; -- native data path width - do not change!
-  constant hw_version_c : std_ulogic_vector(31 downto 0) := x"01070307"; -- NEORV32 version - no touchy!
+  constant hw_version_c : std_ulogic_vector(31 downto 0) := x"01070308"; -- NEORV32 version - no touchy!
   constant archid_c     : natural := 19; -- official RISC-V architecture ID - hands off!
 
   -- Check if we're inside the Matrix -------------------------------------------------------