[tools] Commit memory debug (et al) tooling

These are some changes I made to debug tooling while tracking down the
bugfix in the previous commit.

Each `scripts/debug_*_alloc.gdb` script has gdb output a `*_allocs.txt`
file, which in turn can be parsed by the `scripts/parse_*_allocs.py`
script to find errors.

scripts/parse_buddy_allocs.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env python3
+
+class block:
+    def __init__(self, start, order, free=False):
+        self.start = start
+        self.order = order
+        self.free = free
+
+    @property
+    def end(self):
+        return self.start + (1<<self.order)
+
+    def overlaps(self, other):
+        return other.start < self.end and other.end > self.start
+
+    def __str__(self):
+        return f"[{self.start:016x} {self.order:2} {self.free and 'free' or 'used'}]"
+
+def get_block(blocks, addr, order, reason):
+    b = blocks.get(addr)
+    if b is None:
+        print(f"ERROR: {reason} unknown block [{addr:016x}, {order}]")
+    elif b.order != order:
+        print(f"ERROR: {reason} block {b} for order {order}")
+    else:
+        return b
+    return None
+ 
+def new_block(blocks, addr, order):
+    b = block(addr, order)
+    for existing in blocks.values():
+        if b.overlaps(existing):
+            print(f"ERROR: new block {b} overlaps existing {existing}")
+    blocks[addr] = b
+
+def free_block(blocks, addr, order, free):
+    s = free and "freeing" or "popping"
+    b = get_block(blocks, addr, order, s)
+    if b and b.free == free:
+        print(f"ERROR: {s} block {b}")
+    elif b:
+        b.free = free
+
+def split_block(blocks, addr, order):
+    b = get_block(blocks, addr, order+1, "splitting")
+    if b:
+        b.order = order
+        buddy = b.start ^ (1<<order)
+        blocks[buddy] = block(buddy, order)
+
+def merge_blocks(blocks, addr1, addr2, order):
+    b1 = get_block(blocks, addr1, order, "merging")
+    b2 = get_block(blocks, addr2, order, "merging")
+    if b1.start > b2.start:
+        b1, b2 = b2, b1
+    del blocks[b2.start]
+    b1.order = order + 1
+
+def parse_line(blocks, line):
+    args = line.strip().split()
+    match args:
+        case ['N', addr, order]:
+            new_block(blocks, int(addr, base=16), int(order))
+        case ['n', addr, order]:
+            new_block(blocks, int(addr, base=16), int(order))
+        case ['P', addr, order]:
+            free_block(blocks, int(addr, base=16), int(order), False)
+        case ['p', addr, order]:
+            free_block(blocks, int(addr, base=16), int(order), False)
+        case ['F', addr, order]:
+            free_block(blocks, int(addr, base=16), int(order), True)
+        case ['S', addr, order]:
+            split_block(blocks, int(addr, base=16), int(order))
+        case ['M', addr1, addr2, order]:
+            merge_blocks(blocks, int(addr1, base=16), int(addr2, base=16), int(order))
+        case _:
+            pass
+
+def parse_file(f):
+    blocks = {}
+    for line in f.readlines():
+        parse_line(blocks, line)
+
+    #for addr in sorted(blocks.keys()):
+    #    print(f"{addr:09x}: {blocks[addr]}")
+
+if __name__ == "__main__":
+    import sys
+    if len(sys.argv) > 1:
+        with open(sys.argv[1]) as f:
+            parse_file(f)
+    else:
+        parse_file(sys.stdin)