Go runtime value dumping (#2329)

* basic go value dumping

* better error handling and misc improvements

* minor documentation changes

* satisfy mypy

* struct parsing and bug fix

* satisfy mypy

* deal with evacuated buckets

* better error message for invalid expressions

* convert bytearray to bytes before repr

* support for recursive types and better type dumping

* better QOL for go-dump command

* formatting options and debug/pretty printing

* add go dumping unit tests

* deal with differences in old go version

* lint

* old go versions missing any alias

* proper name dumping for go versions prior to 1.17

* lint

* go is being weird on CI

* warn instead of erroring

* function and interface dumping

pwndbg/commands/__init__.py

@@ -713,6 +713,7 @@ def load_commands() -> None:
         import pwndbg.commands.elf
         import pwndbg.commands.flags
         import pwndbg.commands.ghidra
+        import pwndbg.commands.godbg
         import pwndbg.commands.got
         import pwndbg.commands.got_tracking
         import pwndbg.commands.heap

pwndbg/commands/godbg.py

@@ -0,0 +1,95 @@
+from __future__ import annotations
+
+import argparse
+
+import pwndbg.commands
+import pwndbg.gdblib.arch
+import pwndbg.gdblib.config
+import pwndbg.gdblib.godbg
+import pwndbg.gdblib.memory
+import pwndbg.gdblib.regs
+from pwndbg.commands import CommandCategory
+
+parser = argparse.ArgumentParser(
+    description="Dumps a Go value of a given type at a specified address."
+)
+parser.add_argument(
+    "ty",
+    type=str,
+    help="Go type of value to dump, e.g. map[int]string, or the address of a type to resolve at runtime, e.g. 0x408860",
+)
+parser.add_argument(
+    "address",
+    type=pwndbg.commands.AddressExpr,
+    help="Address to dump",
+)
+parser.add_argument("-x", "--hex", action="store_true", help="Display non-pointer integers as hex")
+parser.add_argument(
+    "-f",
+    "--decimals",
+    nargs="?",
+    type=int,
+    help="Configures the number of decimal places to display for floating points",
+)
+
+parser.add_argument(
+    "-d",
+    "--debug",
+    action="store_true",
+    help="Shows debug info, like addresses for slice/map elements, slice capacity, etc.",
+)
+
+parser.add_argument(
+    "-p",
+    "--pretty",
+    action="store_true",
+    help="Enables pretty printing",
+)
+
+
+@pwndbg.commands.ArgparsedCommand(
+    parser, category=CommandCategory.MEMORY, command_name="go-dump", aliases=["god"]
+)
+@pwndbg.commands.OnlyWhenRunning
+def go_dump(
+    ty: str, address: int, hex: bool, decimals: int | None, debug: bool, pretty: bool
+) -> None:
+    try:
+        ty_addr = int(ty, 0)
+        (_, parsed_ty) = pwndbg.gdblib.godbg.decode_runtime_type(ty_addr)
+        if parsed_ty is None:
+            print("Failed to decode runtime type.")
+            return
+    except ValueError:
+        parsed_ty = pwndbg.gdblib.godbg.parse_type(ty)
+    fmt = pwndbg.gdblib.godbg.FormatOpts(
+        int_hex=hex, float_decimals=decimals, debug=debug, pretty=pretty
+    )
+    print(parsed_ty.dump(address, fmt))
+
+
+parser = argparse.ArgumentParser(
+    description="Dumps a Go runtime reflection type at a specified address."
+)
+parser.add_argument(
+    "address",
+    type=pwndbg.commands.AddressExpr,
+    help="Address to dump",
+)
+
+
+@pwndbg.commands.ArgparsedCommand(
+    parser, category=CommandCategory.MEMORY, command_name="go-type", aliases=["goty"]
+)
+@pwndbg.commands.OnlyWhenRunning
+def go_type(address: int) -> None:
+    meta, ty = pwndbg.gdblib.godbg.decode_runtime_type(address, True)
+    print(f" Name: {meta.name}")
+    print(f" Kind: {meta.kind.name}")
+    print(f" Size: {meta.size} ({meta.size:#x})")
+    print(f"Align: {meta.align}")
+    print(f"Parse: {ty}")
+    if ty:
+        data = ty.additional_metadata()
+        if data:
+            print("\n".join(data))

tests/gdb-tests/tests/binaries/gosample.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+func testFunc(x interface{}) *interface{} {
+	fmt.Println(x)
+	return &x // leak x to force it to be allocated somewhere
+}
+
+func main() {
+	testFunc(map[string]int{"a": 1, "b": 2, "c": 3})
+	testFunc([]struct {
+		a int
+		b string
+	}{{a: 1, b: "first"}, {a: 2, b: "second"}})
+	testFunc([3]complex64{1.1 + 2.2i, -2.5 - 5i, 4.2 - 2.1i})
+}

tests/gdb-tests/tests/binaries/gosample.x64.go

@@ -1,3 +0,0 @@
-package main
-
-func main() {}

tests/gdb-tests/tests/binaries/gosample.x86.go

@@ -1,3 +0,0 @@
-package main
-
-func main() {}

tests/gdb-tests/tests/binaries/makefile

@@ -19,7 +19,7 @@ EXTRA_FLAGS_ASM =
 
 GO              =	   go
 SOURCES_GO      =	   $(wildcard *.go)
-COMPILED_GO     =	   $(SOURCES_GO:.go=)
+COMPILED_GO     =	   $(SOURCES_GO:.go=.x86) $(SOURCES_GO:.go=.x64)
 
 ifeq ($(TARGET), x86)
 CFLAGS		  +=	  -m32
@@ -54,14 +54,14 @@ all: $(LINKED) $(LINKED_ASM) $(COMPILED_GO) $(CUSTOM_TARGETS)
 	@echo "[+] Linking '$@'"
 	@$(LD) -Ttext 0x400080 --section-start .note.gnu.property=0x8000000 -o $@ $?
 
-%.x86 : %.x86.go
+%.x86 : %.go
 	@echo "[+] Building '$@'"
-	@GOARCH=386 $(GO) build $?
+	@GOARCH=386 $(GO) build -gcflags "-N -l" -o $@ $?
 	@# Not stripped on purpose
 
-%.x64 : %.x64.go
+%.x64 : %.go
 	@echo "[+] Building '$@'"
-	@GOARCH=amd64 $(GO) build $?
+	@GOARCH=amd64 $(GO) build -gcflags "-N -l" -o $@ $?
 	@# Not stripped on purpose
 
 heap_bugs.out: heap_bugs.c

tests/gdb-tests/tests/test_go.py

@@ -8,7 +8,7 @@ GOSAMPLE_X64 = tests.binaries.get("gosample.x64")
 GOSAMPLE_X86 = tests.binaries.get("gosample.x86")
 
 
-def test_typeinfo_go_x64(start_binary):
+def test_typeinfo_go_x64():
     """
     Tests pwndbg's typeinfo knows about the Go x64 types.
     Catches: Python Exception <class 'gdb.error'> No type named u8.:
@@ -19,7 +19,7 @@ def test_typeinfo_go_x64(start_binary):
     assert "Python Exception" not in start
 
 
-def test_typeinfo_go_x86(start_binary):
+def test_typeinfo_go_x86():
     """
     Tests pwndbg's typeinfo knows about the Go x32 types
     Catches: Python Exception <class 'gdb.error'> No type named u8.:
@@ -28,3 +28,29 @@ def test_typeinfo_go_x86(start_binary):
     gdb.execute("file " + GOSAMPLE_X86)
     start = gdb.execute("start", to_string=True)
     assert "Python Exception" not in start
+
+
+def helper_test_dump(start_binary, filename):
+    gdb.execute("set environment GOMAXPROCS=1")
+    start_binary(filename)
+    gdb.execute("break gosample.go:6", to_string=True)
+    gdb.execute("continue")
+    first = gdb.execute("go-dump any &x", to_string=True)
+    assert first.strip() == """(map[string]int) &{"a": 1, "b": 2, "c": 3}"""
+    gdb.execute("continue")
+    second = gdb.execute("go-dump any &x", to_string=True)
+    assert (
+        second.strip()
+        == """([]struct { a int; b string }) [struct {a: 1, b: "first"}, struct {a: 2, b: "second"}]"""
+    )
+    gdb.execute("continue")
+    third = gdb.execute("go-dump -f 1 any &x", to_string=True)
+    assert third.strip() == """([3]complex64) [(1.1 + 2.2i), (-2.5 - 5.0i), (4.2 - 2.1i)]"""
+
+
+def test_go_dumping_x64(start_binary):
+    helper_test_dump(start_binary, GOSAMPLE_X64)
+
+
+def test_go_dumping_x86(start_binary):
+    helper_test_dump(start_binary, GOSAMPLE_X86)