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// Richard CPU
// Copyright (C) 2026 Richard Qin
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// File path: rtl/core/pmp_checker.sv
// Description: RISC-V Physical Memory Protection access checker.
module pmp_checker
import rv64_pkg::*;
import csr_pkg::*;
#(
parameter int PHYS_ADDR_WIDTH = 56
)(
input logic req_valid,
input logic [XLEN-1:0] req_paddr,
input logic [3:0] req_size,
input logic req_is_fetch,
input logic req_is_store,
input logic [1:0] priv_mode,
input pmpcfg_entry_t pmpcfg_entries [PMP_ENTRY_COUNT],
input pmpaddr_entry_t pmpaddr_entries [PMP_ENTRY_COUNT],
output logic access_fault
);
localparam logic [1:0] PRIV_MODE_M = 2'b11;
typedef struct packed {
logic valid;
logic [XLEN-1:0] lower_bound;
logic [XLEN-1:0] upper_bound;
} pmp_region_t;
function automatic logic [XLEN-1:0] pmpaddr_to_paddr(input pmpaddr_entry_t pmpaddr);
logic [XLEN-1:0] paddr;
paddr = pmpaddr << 2;
if (PHYS_ADDR_WIDTH < XLEN) begin
paddr[XLEN-1:PHYS_ADDR_WIDTH] = '0;
end
return paddr;
endfunction
function automatic int unsigned napot_trailing_ones(input pmpaddr_entry_t pmpaddr);
int unsigned ones;
ones = 0;
for (int bit_idx = 0; bit_idx < (PHYS_ADDR_WIDTH - 2); bit_idx++) begin
if (pmpaddr[bit_idx]) begin
ones++;
end else begin
break;
end
end
return ones;
endfunction
function automatic pmp_region_t pmp_region(input int unsigned entry_idx);
pmp_region_t region;
logic [1:0] address_matching;
int unsigned ones;
logic [XLEN-1:0] napot_mask;
logic [XLEN-1:0] napot_base;
region.valid = 1'b0;
region.lower_bound = '0;
region.upper_bound = '0;
address_matching = pmpcfg_entries[entry_idx][PMPCFG_A_HI:PMPCFG_A_LO];
unique case (address_matching)
PMP_MODE_OFF: begin
region.valid = 1'b0;
end
PMP_MODE_TOR: begin
region.valid = 1'b1;
region.lower_bound = (entry_idx == 0) ? '0 : pmpaddr_to_paddr(pmpaddr_entries[entry_idx - 1]);
region.upper_bound = pmpaddr_to_paddr(pmpaddr_entries[entry_idx]);
if (region.upper_bound <= region.lower_bound) begin
region.valid = 1'b0;
end
end
PMP_MODE_NA4: begin
region.valid = 1'b1;
region.lower_bound = pmpaddr_to_paddr(pmpaddr_entries[entry_idx]);
region.upper_bound = region.lower_bound + 64'd4;
end
PMP_MODE_NAPOT: begin
region.valid = 1'b1;
ones = napot_trailing_ones(pmpaddr_entries[entry_idx]);
napot_mask = (64'd1 << (ones + 1)) - 64'd1;
napot_base = (pmpaddr_entries[entry_idx] & ~napot_mask) << 2;
if (PHYS_ADDR_WIDTH < XLEN) begin
napot_base[XLEN-1:PHYS_ADDR_WIDTH] = '0;
end
region.lower_bound = napot_base;
region.upper_bound = napot_base + (64'd1 << (ones + 3));
end
default: begin
region.valid = 1'b0;
end
endcase
return region;
endfunction
function automatic logic ranges_overlap(
input logic [XLEN-1:0] access_lower,
input logic [XLEN-1:0] access_upper,
input logic [XLEN-1:0] region_lower,
input logic [XLEN-1:0] region_upper
);
return (access_lower < region_upper) && (access_upper > region_lower);
endfunction
function automatic logic range_contains(
input logic [XLEN-1:0] access_lower,
input logic [XLEN-1:0] access_upper,
input logic [XLEN-1:0] region_lower,
input logic [XLEN-1:0] region_upper
);
return (access_lower >= region_lower) && (access_upper <= region_upper);
endfunction
function automatic logic permissions_allow(
input pmpcfg_entry_t cfg,
input logic is_fetch,
input logic is_store
);
if (is_fetch) begin
return cfg[PMPCFG_X_BIT];
end
if (is_store) begin
return cfg[PMPCFG_W_BIT];
end
return cfg[PMPCFG_R_BIT];
endfunction
always_comb begin
logic [XLEN-1:0] access_lower;
logic [XLEN-1:0] access_upper;
logic [3:0] normalized_size;
logic matched;
pmp_region_t region;
normalized_size = (req_size == 4'd0) ? 4'd1 : req_size;
access_lower = req_paddr;
access_upper = req_paddr + {{(XLEN-4){1'b0}}, normalized_size};
matched = 1'b0;
region = '0;
access_fault = 1'b0;
if (req_valid) begin
for (int unsigned entry_idx = 0; entry_idx < PMP_ENTRY_COUNT; entry_idx++) begin
region = pmp_region(entry_idx);
if (!matched && region.valid &&
ranges_overlap(access_lower, access_upper, region.lower_bound, region.upper_bound)) begin
matched = 1'b1;
if (!range_contains(access_lower, access_upper, region.lower_bound, region.upper_bound)) begin
access_fault = 1'b1;
end else if ((priv_mode != PRIV_MODE_M) || pmpcfg_entries[entry_idx][PMPCFG_L_BIT]) begin
access_fault = !permissions_allow(pmpcfg_entries[entry_idx], req_is_fetch, req_is_store);
end
end
end
if (!matched && (priv_mode != PRIV_MODE_M)) begin
access_fault = 1'b1;
end
end
end
endmodule
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