From 2520f38555c9afcd6bec50116807f8bf97311d43 Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Fri, 25 Oct 2019 20:42:48 +0200
Subject: added some notes about debugging
---
debug.txt | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
gdb.txt | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 101 insertions(+), 5 deletions(-)
create mode 100644 debug.txt
diff --git a/debug.txt b/debug.txt
new file mode 100644
index 0000000..5a3c105
--- /dev/null
+++ b/debug.txt
@@ -0,0 +1,48 @@
+.:: debugging ::.
+--------------------------------------------------------------------------------
+
+# print syscalls of process with all threads (-f) of running process
+strace -f -p <pid>
+# only trace certain syscalls
+strace -f -p <pid> -e trace=open,socket
+# trace signals delivered to process
+strace -f -p <pid> -e signal
+
+# dump stack of process and all threads
+pstack <pid>
+
+# print file flags
+# +fg print file flag abbreviations
+lsof +fg -p <pid>
+
+# print process virt mem map
+# compared to /proc/<>/maps it shows the size of the mappings
+pmap <pid>
+
+
+# get supported events
+perf list
+
+perf stat -p <pid>
+perf stat -p <pid> -I <ms>
+perf stat -p <pid> -e cycles,faults,cache-misses,context-switches
+
+# -K hide kernel threads
+perf top -F 99 -p <pid> -K
+
+perf record -F 99 -p <pid>
+perf record -F 99 -p <pid> --call-graph dwarf
+perf record -F 99 -p <pid> -e instructions,cpu-cycles,faults,cache-misses,context-switches
+
+
+# print supported events
+ophelp
+
+operf -p <pid>
+
+opreport -c
+opreport -l
+
+--------------------------------------------------------------------------------
+vim:sts=2:et:tw=80:cc=80:fo+=t:ft=help
+
diff --git a/gdb.txt b/gdb.txt
index 47ecdce..37b6b48 100644
--- a/gdb.txt
+++ b/gdb.txt
@@ -8,6 +8,7 @@
|prompt|
|user_commands|
|hooks|
+ |flows|
# gdb(1) *gdb*
=========
@@ -30,7 +31,7 @@
specify which process to follow on fork(2)
sharedlibrary [regex]
- load symbols of shared lib, if regex then only symbols
+ load symbols of shared lib, if REGEX then only symbols
for matching libs
break <sym> thread <tnum>
@@ -41,20 +42,34 @@
so 'rbreak foo' matches barfoobar()
command [bp_list] define commands to run after breakpoint hit if
- bp_list not supplied attach command to last
+ BP_LIST not supplied attach command to last
created bp
- bp_list: space separates list, eg 'command 2 5-8'
+ BP_LIST: space separates list, eg 'command 2 5-8'
to run command for bp 2,5,6,7,8
info functions [regex]
- list functions according to regex, if regex empty,
+ list functions according to REGEX, if REGEX empty,
list all
info variables [regex]
- list variables according to regex, if regex empty,
+ list variables according to REGEX, if REGEX empty,
list all
+ info handle [signal]
+ list bevahior for SIGNAL, if SIGNAL empty list all signals
+
+ handle signal <action>
+ configure how gdb handles SIGNAL which is ment for the debugee
+ <action>:
+ stop/nostop catch signal in gdb and break
+ print/noprint print message when gdb catches signal
+ pass/nopass pass signal down to debugee
+ noignore/ignore synonyms for
+
+ catch signal <signal>
+ create a catchpoint for SIGNAL
+
user commands: *user_commands*
define <cmd> defines user command <cmd> to be run
@@ -78,6 +93,39 @@
# cmds executing <cmd>
end
+
+ flows: *flows*
+ # catch SIGSEGV and execute some actions once it happends
+ - script:
+ catch signal SIGSEGV
+ command
+ bt
+ ct
+ end
+
+ # quickly execute gdb command on running process, eg get backtrace from
+ # thread 1
+ - cmd:
+ $> gdb -ex 'thread 1' -ex 'bt' -p <PID>
+
+ # script gdb for automating debugging sessions
+ - script: run.gdb
+ set pagination off
+
+ break mmap
+ command
+ info reg rdi rsi rdx
+ bt
+ c
+ end
+
+ #initial drop
+ c
+
+ - cmd:
+ $> gdb -p <PID> -x ./run.gdb --batch &> run.log
+
+
--------------------------------------------------------------------------------
vim:sts=2:et:tw=80:cc=80:fo+=t:ft=help
--
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