mallocng: Add ng-metaarea and ng-ctx commands (#3164)

* add missing type annotations

* ng-metaarea to dump meta_area objects

* ng-ctx: command to dump the __malloc_context object

* autogen docs

* properly bail if we cant find the __malloc_context

* take the p var out of `from_start`

docs/commands/index.md

@@ -260,6 +260,8 @@
 -  [mallocng-explain](musl/mallocng-explain.md) - Gives a quick explanation of musl's mallocng allocator.
 -  [mallocng-find](musl/mallocng-find.md) - Find slot which contains the given address.
 -  [mallocng-group](musl/mallocng-group.md) - Print out information about a mallocng group at the given address.
+-  [mallocng-malloc-context](musl/mallocng-malloc-context.md) - Print out the mallocng __malloc_context (ctx) object.
+-  [mallocng-meta-area](musl/mallocng-meta-area.md) - Print out a mallocng meta_area object at the given address.
 -  [mallocng-meta](musl/mallocng-meta.md) - Print out information about a mallocng group given the address of its meta.
 -  [mallocng-slot-start](musl/mallocng-slot-start.md) - Dump information about a mallocng slot, given its start address.
 -  [mallocng-slot-user](musl/mallocng-slot-user.md) - Dump information about a mallocng slot, given its user address.

docs/commands/musl/mallocng-malloc-context.md

@@ -0,0 +1,25 @@
+<!-- THIS PART OF THIS FILE IS AUTOGENERATED. DO NOT MODIFY IT. See scripts/generate-docs.sh -->
+# mallocng-malloc-context
+
+```text
+usage: mallocng-malloc-context [-h] [address]
+
+```
+
+Print out the mallocng __malloc_context (ctx) object.
+
+**Alias:** ng-ctx
+### Positional arguments
+
+|Positional Argument|Help|
+| :--- | :--- |
+|address|Use the provided address instead of the one Pwndbg found.|
+
+### Optional arguments
+
+|Short|Long|Help|
+| :--- | :--- | :--- |
+|-h|--help|show this help message and exit|
+
+<!-- END OF AUTOGENERATED PART. Do not modify this line or the line below, they mark the end of the auto-generated part of the file. If you want to extend the documentation in a way which cannot easily be done by adding to the command help description, write below the following line. -->
+<!-- ------------\>8---- ----\>8---- ----\>8------------ -->

docs/commands/musl/mallocng-meta-area.md

@@ -0,0 +1,25 @@
+<!-- THIS PART OF THIS FILE IS AUTOGENERATED. DO NOT MODIFY IT. See scripts/generate-docs.sh -->
+# mallocng-meta-area
+
+```text
+usage: mallocng-meta-area [-h] address
+
+```
+
+Print out a mallocng meta_area object at the given address.
+
+**Alias:** ng-metaarea
+### Positional arguments
+
+|Positional Argument|Help|
+| :--- | :--- |
+|address|The address of the meta_area object.|
+
+### Optional arguments
+
+|Short|Long|Help|
+| :--- | :--- | :--- |
+|-h|--help|show this help message and exit|
+
+<!-- END OF AUTOGENERATED PART. Do not modify this line or the line below, they mark the end of the auto-generated part of the file. If you want to extend the documentation in a way which cannot easily be done by adding to the command help description, write below the following line. -->
+<!-- ------------\>8---- ----\>8---- ----\>8------------ -->

pwndbg/aglib/heap/mallocng.py

@@ -22,9 +22,9 @@ import pwndbg.color.message as message
 
 # https://elixir.bootlin.com/musl/v1.2.5/source/src/malloc/mallocng/meta.h#L14
 # Slot granularity.
-UNIT = 16
+UNIT: int = 16
 # Size of in-band metadata.
-IB = 4
+IB: int = 4
 
 # https://elixir.bootlin.com/musl/v1.2.5/source/src/malloc/mallocng/malloc.c#L12
 # Describes the possible sizes a slot can be. These are `/ UNIT`.
@@ -47,7 +47,7 @@ class SlotState(Enum):
 
 
 # Shorthand
-def int_size():
+def int_size() -> int:
     return pwndbg.aglib.typeinfo.sint.sizeof
 
 
@@ -548,13 +548,11 @@ class Slot:
         sn3 = memory.u8(start - 3)
         if sn3 == 224:
             off = memory.u16(start - 2)
-            p = start + off * UNIT
-            obj = cls(p)
+            obj = cls(start + off * UNIT)
             obj._sn3 = sn3
         else:
             # freed / avail slots will also go into this branch.
-            p = start
-            obj = cls(p)
+            obj = cls(start)
             obj._sn3 = obj._pn3 = sn3
 
         obj._start = start
@@ -784,7 +782,7 @@ class Meta:
     # Semi-custom methods..
 
     @property
-    def stride(self):
+    def stride(self) -> int:
         """
         Returns -1 if sizeclass >= len(size_classes).
         """
@@ -804,7 +802,7 @@ class Meta:
     # Custom methods..
 
     @property
-    def cnt(self):
+    def cnt(self) -> int:
         """
         Number of slots in the group.
         """
@@ -851,7 +849,7 @@ class Meta:
             return SlotState.ALLOCATED
 
     @staticmethod
-    def sizeof():
+    def sizeof() -> int:
         return 2 * int_size() + 4 * pwndbg.aglib.arch.ptrsize
 
 
@@ -878,7 +876,7 @@ class MetaArea:
 
         self.load()
 
-    def load(self):
+    def load(self) -> None:
         ptrsize = pwndbg.aglib.arch.ptrsize
         uint64size = pwndbg.aglib.typeinfo.uint64.sizeof
         endian = pwndbg.aglib.arch.endian
@@ -909,6 +907,14 @@ class MetaArea:
         """
         return self.slots + idx * Meta.sizeof()
 
+    @property
+    def area_size(self) -> int:
+        """
+        Returns not the size of `struct meta_area` but rather
+        the size of the memory this object represents.
+        """
+        return (self.slots - self.addr) + self.nslots * Meta.sizeof()
+
 
 class MallocContext:
     """
@@ -965,7 +971,7 @@ class MallocContext:
         # evaluation.
         self.load()
 
-    def load(self):
+    def load(self) -> None:
         ptrsize = pwndbg.aglib.arch.ptrsize
         size_tsize = pwndbg.aglib.typeinfo.size_t.sizeof
         unsignedsize = pwndbg.aglib.typeinfo.uint.sizeof
@@ -1059,7 +1065,7 @@ class Mallocng(pwndbg.aglib.heap.heap.MemoryAllocator):
     before you used the object.
     """
 
-    def __init__(self):
+    def __init__(self) -> None:
         self.finished_init: bool = False
 
         self.ctx_addr: int = 0
@@ -1068,16 +1074,21 @@ class Mallocng(pwndbg.aglib.heap.heap.MemoryAllocator):
         self.secret: bytearray = b""
         self.hope: bool = True
 
-    def init_if_needed(self):
+    def init_if_needed(self) -> bool:
         """
         We want this class to be a singleton, but also we can't
         initialize it as soon as pwndbg is loaded.
 
         Users of the object are responsible for calling this to
         make sure the object is initialized.
+
+        Returns:
+            True if this object is successfully initialized (whether
+            now or before). False otherswise. If this returns False
+            you may not use this object for heap operations.
         """
         if self.finished_init:
-            return
+            return self.hope
 
         self.ctx_addr = 0
         self.ctx = None
@@ -1090,9 +1101,13 @@ class Mallocng(pwndbg.aglib.heap.heap.MemoryAllocator):
         if self.ctx_addr and self.hope:
             self.ctx = MallocContext(self.ctx_addr)
 
+        # We will try to reinitialize again if we failed now.
+        if self.hope:
             self.finished_init = True
 
-    def set_ctx_addr(self):
+        return self.hope
+
+    def set_ctx_addr(self) -> None:
         """
         Find where the __malloc_context global symbol is. Try using debug information,
         but if it isn't available try using a heuristic.
@@ -1152,7 +1167,7 @@ class Mallocng(pwndbg.aglib.heap.heap.MemoryAllocator):
                     return
 
             for addr, mapname in possible:
-                if mapname.contains("libc"):
+                if "libc" in mapname:
                     self.ctx_addr = addr
                     return
 

pwndbg/commands/mallocng.py

@@ -554,7 +554,11 @@ def smart_dump_slot(
 
         # If it wasn't provided to us, let's try to search for it now.
         output += "Could not load valid meta from local information, searching the heap.. "
-        ng.init_if_needed()
+
+        if not ng.init_if_needed():
+            output += message.error("\nCouldn't find the allocator, aborting the search. ")
+            gslot, fslot = None, None
+        else:
             gslot, fslot = ng.find_slot(slot.p, False, False)
 
         if gslot is None:
@@ -581,6 +585,84 @@ def smart_dump_slot(
     return output
 
 
+def dump_meta_area(meta_area: mallocng.MetaArea) -> str:
+    area_range = (
+        "@ "
+        + C.memory.get(meta_area.addr)
+        + " - "
+        + C.memory.get(meta_area.addr + meta_area.area_size)
+    )
+
+    pp = PropertyPrinter()
+
+    pp.start_section("meta_area", area_range)
+    pp.add(
+        [
+            Property(name="check", value=meta_area.check),
+            Property(name="next", value=meta_area.next, is_addr=True),
+            Property(name="nslots", value=meta_area.nslots),
+            Property(name="slots", value=meta_area.slots, is_addr=True),
+        ]
+    )
+    return pp.dump()
+
+
+def dump_malloc_context(ctx: mallocng.MallocContext) -> str:
+    ctx_addr = "@ " + C.memory.get(ctx.addr)
+
+    pp = PropertyPrinter(22)
+    pp.start_section("ctx", ctx_addr)
+    props = [
+        Property(name="secret", value=ctx.secret),
+    ]
+    if ctx.has_pagesize_field:
+        props.append(
+            Property(name="pagesize", value=ctx.pagesize),
+        )
+
+    props.extend(
+        [
+            Property(name="init_done", value=ctx.init_done),
+            Property(name="mmap_counter", value=ctx.mmap_counter),
+            Property(name="free_meta_head", value=ctx.free_meta_head, is_addr=True),
+            Property(name="avail_meta", value=ctx.avail_meta, is_addr=True),
+            Property(name="avail_meta_count", value=ctx.avail_meta_count),
+            Property(name="avail_meta_area_count", value=ctx.avail_meta_area_count),
+            Property(name="meta_alloc_shift", value=ctx.meta_alloc_shift),
+            Property(name="meta_area_head", value=ctx.meta_area_head, is_addr=True),
+            Property(name="meta_area_tail", value=ctx.meta_area_tail, is_addr=True),
+            Property(name="avail_meta_areas", value=ctx.avail_meta_areas, is_addr=True),
+        ]
+    )
+
+    for i in range(len(ctx.active)):
+        if ctx.active[i] != 0:
+            props.append(Property(name=f"active[{i}]", value=ctx.active[i], is_addr=True))
+
+    for i in range(len(ctx.usage_by_class)):
+        if ctx.usage_by_class[i] != 0:
+            props.append(Property(name=f"usage_by_class[{i}]", value=ctx.usage_by_class[i]))
+
+    for i in range(len(ctx.unmap_seq)):
+        if ctx.unmap_seq[i] != 0:
+            props.append(Property(name=f"unmap_seq[{i}]", value=ctx.unmap_seq[i]))
+
+    for i in range(len(ctx.bounces)):
+        if ctx.bounces[i] != 0:
+            props.append(Property(name=f"bounces[{i}]", value=ctx.bounces[i]))
+
+    props.extend(
+        [
+            Property(name="seq", value=ctx.seq),
+            Property(name="brk", value=ctx.brk, is_addr=True),
+        ]
+    )
+
+    pp.add(props)
+
+    return pp.dump()
+
+
 parser = argparse.ArgumentParser(
     description="""
 Dump information about a mallocng slot, given its user address.
@@ -730,6 +812,77 @@ def mallocng_group(address: int) -> None:
         return
 
 
+parser = argparse.ArgumentParser(
+    description="""
+Print out a mallocng meta_area object at the given address.
+    """,
+)
+parser.add_argument(
+    "address",
+    type=int,
+    help="The address of the meta_area object.",
+)
+
+
+@pwndbg.commands.Command(
+    parser,
+    category=CommandCategory.MUSL,
+    aliases=["ng-metaarea"],
+)
+@pwndbg.commands.OnlyWhenRunning
+def mallocng_meta_area(address: int) -> None:
+    if not memory.is_readable_address(address):
+        print(message.error(f"Address {address:#x} not readable."))
+        return
+
+    try:
+        meta_area = mallocng.MetaArea(address)
+        print(dump_meta_area(meta_area), end="")
+    except pwndbg.dbg_mod.Error as e:
+        print(message.error(str(e)))
+        return
+
+
+parser = argparse.ArgumentParser(
+    description="""
+Print out the mallocng __malloc_context (ctx) object.
+    """,
+)
+parser.add_argument(
+    "address",
+    nargs="?",
+    type=int,
+    help="Use the provided address instead of the one Pwndbg found.",
+)
+
+
+@pwndbg.commands.Command(
+    parser,
+    category=CommandCategory.MUSL,
+    aliases=["ng-ctx"],
+)
+@pwndbg.commands.OnlyWhenRunning
+def mallocng_malloc_context(address: Optional[int] = None) -> None:
+    if address is None:
+        if not ng.init_if_needed():
+            print(message.error("Couldn't find the allocator, aborting the command."))
+            return
+
+        ctx = ng.ctx
+    else:
+        if not memory.is_readable_address(address):
+            print(message.error(f"Address {address:#x} not readable."))
+            return
+
+        try:
+            ctx = mallocng.MallocContext(address)
+        except pwndbg.dbg_mod.Error as e:
+            print(message.error(str(e)))
+            return
+
+    print(dump_malloc_context(ctx), end="")
+
+
 parser = argparse.ArgumentParser(
     description="""
 Find slot which contains the given address.
@@ -779,7 +932,9 @@ def mallocng_find(
         print(message.error(f"Address {hex(address)} not readable."))
         return
 
-    ng.init_if_needed()
+    if not ng.init_if_needed():
+        print(message.error("Couldn't find the allocator, aborting the command."))
+        return
 
     grouped_slot, slot = ng.find_slot(address, metadata, shallow)