Submission by Hafsa-shoaib989: IDL Programming Challenge Solution

submissions/Hafsa-shoaib989/pmp_checker.py

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+import sys
+
+# Count the number of trailing 1s in the binary representation of n.
+def count_trailing_ones(n):
+    if n == 0:
+        return 0
+    count = 0
+    while (n & 1) == 1:
+        count += 1
+        n >>= 1
+    return count
+
+def main():
+    if len(sys.argv) != 5:
+        print("Usage: program <pmp_config> <address> <mode> <operation>")
+        sys.exit(1)
+
+    config_file = sys.argv[1]
+    address_str = sys.argv[2]
+    mode = sys.argv[3]
+    operation = sys.argv[4]
+
+    address = int(address_str, 16)   # Parse the physical address (hex with 0x prefix)
+
+    try:
+        with open(config_file, 'r') as f:
+            lines = [line.strip() for line in f.readlines()]
+    except FileNotFoundError:
+        print(f"Error: File {config_file} not found.")
+        sys.exit(1)
+
+    if len(lines) != 128:
+        print("Invalid PMP configuration file: expected 128 lines.")
+        sys.exit(1)
+
+    # Parse PMPcfg and PMPaddr entries
+    cfgs = []
+    addrs = []
+    for i in range(64):
+        cfg_line = lines[i]
+        cfgs.append(int(cfg_line, 16))
+
+    for i in range(64, 128):
+        addr_line = lines[i]
+        addrs.append(int(addr_line, 16))
+
+    # Check each PMP entry in order (0 to 63)
+    matching_entry = None
+    for i in range(64):
+        cfg = cfgs[i]
+        # Extract fields from cfg byte
+        L = (cfg >> 7) & 0x1
+        A = (cfg >> 3) & 0x3
+        X = (cfg >> 2) & 0x1
+        W = (cfg >> 1) & 0x1
+        R = cfg & 0x1
+
+        if A == 0:
+            continue  # Entry is disabled
+
+        pmpaddr = addrs[i]
+        pmpaddr_val = pmpaddr << 2  # Shift left by 2 to get actual address part
+
+        # Determine address range based on A field
+        if A == 1:  # TOR (Top of Range)
+            if i == 0:
+                lower = 0
+                upper = pmpaddr_val
+            else:
+                prev_pmpaddr = addrs[i-1] << 2
+                lower = prev_pmpaddr
+                upper = pmpaddr_val
+
+            if lower >= upper:
+                continue  # Invalid range, no match
+
+            if address >= lower and address < upper:
+                matching_entry = (L, R, W, X)
+                break
+
+        elif A == 2:  # NA4 (Naturally Aligned 4-byte)
+            start = pmpaddr_val
+            end = start + 4
+            if address >= start and address < end:
+                matching_entry = (L, R, W, X)
+                break
+
+        elif A == 3:  # NAPOT (Naturally Aligned Power-of-Two)
+            trailing_ones = count_trailing_ones(pmpaddr)
+            size = 2 ** (trailing_ones + 3)
+            base = (pmpaddr_val) & ~(size - 1)
+            end = base + size
+            if address >= base and address < end:
+                matching_entry = (L, R, W, X)
+                break
+
+    # Determine access fault
+    if matching_entry is not None:
+        L, R, W, X = matching_entry
+        # Check permissions
+        if mode == 'M' and L == 0:
+            allowed = True
+        else:
+            if operation == 'R':
+                allowed = (R == 1)
+            elif operation == 'W':
+                allowed = (W == 1)
+            elif operation == 'X':
+                allowed = (X == 1)
+            else:
+                allowed = False  # Invalid operation (unreachable per problem statement)
+
+        print("Access Fault" if not allowed else "No Access Fault")
+    else:
+        # No matching entry
+        if mode == 'M':
+            print("No Access Fault")
+        else:
+            # S or U mode, and PMP entries are implemented (all 64 in config)
+            print("Access Fault")
+
+if __name__ == "__main__":
+    main()

submissions/Hafsa-shoaib989/pmp_configuration.txt

@@ -0,0 +1,128 @@
+0x0
+0x1
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+0x0
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+0x8000000
+0x100000000
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