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authorjohannst <johannes.stoelp@gmail.com>2020-03-13 21:58:49 +0100
committerjohannst <johannes.stoelp@gmail.com>2020-03-13 21:58:49 +0100
commitc8529af1769235f46b1149a78a6712f61c905c21 (patch)
tree2e4aeb8213b34ccb6b435ef0ea91bd71660322db /src
parent37e14e8bf3c17b57fc3dd1ada14a690b6b5abd3a (diff)
downloadnotes-c8529af1769235f46b1149a78a6712f61c905c21.tar.gz
notes-c8529af1769235f46b1149a78a6712f61c905c21.zip
added mdbook + migrated first chapter as test (gdb)
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+# Summary
+
+- [gdb](./gdb.md)
diff --git a/src/gdb.md b/src/gdb.md
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+# gdb(1)
+
+# CLI
+
+```markdown
+ gdb [opts] [prg [-c coredump | -p pid]]
+ gdb [opts] --args prg <prg-args>
+ opts:
+ -p <pid> attach to pid
+ -c <coredump> use <coredump>
+ -x <file> execute script <file> before prompt
+ -ex <cmd> execute command <cmd> before prompt
+ --tty <tty> set I/O tty for debugee
+```
+
+# Interactive usage
+
+```markdown
+ tty <tty>
+ Set <tty> as tty for debugee.
+ Make sure nobody reads from target tty, easiest is to spawn a shell
+ and run following in target tty:
+ > while true; do sleep 1024; done
+
+ set follow-fork-mode <child | parent>
+ Specify which process to follow when debuggee makes a fork(2)
+ syscall.
+
+ sharedlibrary [<regex>]
+ Load symbols of shared libs loaded by debugee. Optionally use <regex>
+ to filter libs for symbol loading.
+
+ break [-qualified] <sym> thread <tnum>
+ Set a breakpoint only for a specific thread.
+ -qualified: Tred <sym> as fully qualified symbol (quiet handy to set
+ breakpoints on C symbols in C++ contexts)
+
+ rbreak <regex>
+ Set breakpoints matching <regex>, where matching internally is done
+ on: .*<regex>.*
+
+ command [<bp_list>]
+ Define commands to run after breakpoint hit. If <bp_list> is not
+ specified attach command to last created breakpoint. Command block
+ terminated with 'end' token.
+
+ <bp_list>: Space separates list, eg 'command 2 5-8' to run command
+ for breakpoints: 2,5,6,7,8.
+
+ info functions [<regex>]
+ List functions matching <regex>. List all functions if no <regex>
+ provided.
+
+ info variables [<regex>]
+ List variables matching <regex>. List all variables if no <regex>
+ provided.
+
+ info handle [<signal>]
+ Print how to handle <signal>. If no <signal> specified print for all
+ signals.
+
+ handle <signal> <action>
+ Configure how gdb handles <signal> sent to 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.
+
+ catch signal <signal>
+ Create a catchpoint for <signal>.
+```
+
+# User commands (macros)
+
+```markdown
+ define <cmd>
+ # cmds
+ end
+
+ document <cmd>
+ # docu
+ end
+
+ help user-defined List user defined commands.
+ help <cmd> List documentation for command <cmd>.
+```
+
+# Hooks
+
+Gdb allows to create two types of command `hooks` which will be either executed
+before or after a certain command.
+
+```markdown
+ define hook-<cmd> Run commands defined in hook before
+ # cmds executing <cmd>.
+ end
+
+ define hookpost-<cmd> Run commands defined in hookpost after
+ # cmds executing <cmd>.
+ end
+```
+
+# Flows
+
+## Catch SIGSEGV and execute commands on occurrence
+```markdown
+ catch signal SIGSEGV
+ command
+ bt
+ c
+ end
+```
+
+## Run `backtrace` on thread 1 (batch mode)
+```markdown
+ gdb --batch -ex 'thread 1' -ex 'bt' -p <pid>
+```
+
+## Script gdb for automating debugging sessions
+```markdown
+# run.gdb
+ set pagination off
+
+ break mmap
+ command
+ info reg rdi rsi rdx
+ bt
+ c
+ end
+
+ #initial drop
+ c
+```
+This script can be used as:
+```markdown
+ gdb -p <pid> -x ./run.gdb --batch &> run.log
+```
+
+## Workaround `command + finish` bug
+When using `finish` action inside a `command` block, actions after `finish` are
+not executed anymore. To workaround that bug one can create a wrapper function
+which calls `finish`.
+```markdown
+ define handler
+ bt
+ finish
+ info reg rax
+ end
+
+ command
+ handler
+ end
+```