GDB Cheat Sheet

Yayu Wang included in category Linux

2023-01-26 2024-10-19 493 words 3 minutes

Configuration

Save history

1
set history save on

Print

history command

1
C-r (reverse-i-search)`':

address

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  x/nfu addr

  n: How many units to print (default 1).

  f: Format character (like print)
      o - octal
      x - hexadecimal
      d - decimal
      u - unsigned decimal
      t - binary
      f - floating point
      a - address
      c - char
      s - string
      i - instruction

      u: Unit.
      b: Byte,
      h: Half-word (two bytes)
      w: Word (four bytes)
      g: Giant word (eight bytes))

print hex

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p/x variable

show all functions

1
info functions [regexp]

show address info

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info symbol addr

Kernel Debugging

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(gdb) apropos lx
function lx_current -- Return current task
function lx_module -- Find module by name and return the module variable
function lx_per_cpu -- Return per-cpu variable
function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable
function lx_thread_info -- Calculate Linux thread_info from task variable
lx-dmesg -- Print Linux kernel log buffer
lx-lsmod -- List currently loaded modules
lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules

V8

compile

args

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# Build arguments go here.
# See "gn args <out_dir> --list" for available build arguments.
is_component_build = true
is_debug = true
symbol_level = 2
target_cpu = "x64"
use_goma = false
v8_enable_backtrace = true
v8_enable_fast_mksnapshot = true
v8_enable_slow_dchecks = true
v8_optimized_debug = false
v8_expose_symbols = true
v8_symbol_level = 2
cppgc_enable_object_names = true
v8_enable_disassembler = true
v8_enable_gdbjit = true

command

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gn args out/Debug
#----- add args -----#
gn gen out/Debug

debug

gdbinit

v8/tools/gdbinit

functions

job

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2
Print a v8 JavaScript object
Usage: job tagged_ptr

jh

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2
Print content of a v8::internal::Handle
Usage: jh internal_handle

jlh

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2
print-v8-local, jl, jlh
Print content of v8::Local handle.

jco

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2
Print a v8 Code object from an internal code address
Usage: jco pc

jtt

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Print the complete transition tree of the given v8 Map.
Usage: jtt tagged_ptr

jst

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Print the current JavaScript stack trace
Usage: jst

jss

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Skip the jitted stack on x64 to where we entered JS last.
Usage: jss

bta

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Print stack trace with assertion scopes
Usage: bta

heap_find

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Find the location of a given address in V8 pages.
Usage: heap_find address

cpcp

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Prints compressed pointer (raw value) after decompression.
Usage: cpcp compressed_pointer

cpm

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Prints member, compressed or not.
Usage: cpm member

js debug commands

DebugPrint
DebugTrace
SystemBreak
full commands

Radare2

analysis

Command	Description
aa	analyze all
afl	list functions
s sym.main	seek to function

inspecting

Command	Description
pdb	basic block
pdf	function disassembly
afa	function arguments
afv	function variables
af	analyze function

graph output

Command	Description
agfv	Interactive Ascii Art
agfd	Graphviz dot