debug: enhance set_pmp_deny to support alignment checks

- set size considering the minimum PMP granularity supported by the hart.

Signed-off-by: Hiroo HAYASHI <24754036+hirooih@users.noreply.github.com>

Author: hirooih

debug/gdbserver.py

@@ -279,7 +279,7 @@ class MemTestReadInvalid(SimpleMemoryTest):
     def test(self):
         bad_address = self.hart.bad_address
         if self.target.support_set_pmp_deny:
-            self.set_pmp_deny(bad_address)
+            self.set_pmp_deny(bad_address, 4)
             self.gdb.command("monitor riscv set_mem_access progbuf abstract")
         good_address = self.hart.ram + 0x80
 
@@ -2205,7 +2205,7 @@ def test(self):
         # Use NULL if a known-bad address is not provided.
         bad_address = self.hart.bad_address or 0
         if self.target.support_set_pmp_deny:
-            self.set_pmp_deny(bad_address)
+            self.set_pmp_deny(bad_address, 1)
             self.gdb.command("monitor riscv set_mem_access progbuf abstract")
         self.gdb.p(f"fox=(char*)0x{bad_address:08x}")
         output = self.gdb.c()

debug/testlib.py

@@ -1488,9 +1488,32 @@ def parkOtherHarts(self, symbol=None):
         self.gdb.select_hart(self.hart)
         self.gdb.command(f"monitor targets {self.hart.id}")
 
-    def set_pmp_deny(self, address, size=4 * 1024):
+    def ctz(self, i):
+        # count trailing zeros
+        return (i & -i).bit_length() - 1
+
+    def get_minimum_pmp_granularity(self):
+        # Determine the minimum PMP granularity supported by this hart.
+        # cf. RISC-V Privileged Architecture, 3.7.1.1. Address Matching
+        self.gdb.p("$pmpcfg0=0")    # Null region
+        self.gdb.p("$pmpaddr0=-1")  # All ones
+        readback = self.gdb.p("$pmpaddr0")
+        return 2**(self.ctz(readback) + 2)
+
+    def set_pmp_deny(self, address, size):
         # Enable physical memory protection, no permission to access specific
-        # address range (default 4KB).
+        # address range. The size must be a power of two and the address must be
+        # naturally aligned to the size.
+
+        # PMP requires size to be at least the minimum granularity.
+        # The minimum granularity for NAPOT mode is 8 bytes.
+        size = max(size, self.get_minimum_pmp_granularity(), 8)
+
+        if 2**self.ctz(address) < size:
+            raise TestNotApplicable(
+                f"address 0x{address:x} should be naturally aligned to "
+                f"0x{size:x}.")
+
         self.gdb.p("$mseccfg=0x4")  # RLB
         self.gdb.p("$pmpcfg0=0x98") # L, NAPOT, !R, !W, !X
         self.gdb.p("$pmpaddr0="