debugserver

debugserver is a console app that as server for remote gdb debugging. It is installed when a device is marked for development. It can be found in /Developer/usr/bin/debugserver. This is also the process invoked by Xcode to debug applications on the device.

Command line options

debugserver can be invoked with

debugserver [<options>] host:<port> [<prog-name> <arg1> <arg2> ...]

Where options can be:

Option	Effect
-a process	Attach debugserver to process. The process can be a pid or executable name.
-d integer	Assign the waitfor-duration.
-f ?	?
-g	Turn on debugging.
-i integer	Assign the waitfor-interval.
-l filename	Log to file. Set filename to stdout to log to standard output.
-t	Use task ID instead of process ID.
-v	Verbose.
-w ?	?
-x method --launch=method	How to launch the program. Can be one of: auto: Auto-detect the best launch method to use. fork: Launch program using fork(2) and exec(3). posix: Launch program using posix_spawn(2). spring: Launch program via SpringBoard.
--lockdown	Obtain parameters from lockdown (?)

Patching for process attaching

The vanilla debugserver cannot attach to any processes due to lack of entitlement to allow task_for_pid(). An entitlement must be inserted to the binary to allow this.

• 0. cd ~
• 1. Thin the binary because ldid does not support fat binaries:
  

lipo -thin armv6 /Developer/usr/bin/debugserver -output ~/debugserver

• 2. Save for following as ent.xml:

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>com.apple.springboard.debugapplications</key>
	<true/>
	<key>get-task-allow</key>
	<true/>
	<key>task_for_pid-allow</key>
	<true/>
	<key>run-unsigned-code</key>
	<true/>
</dict>
</plist>

• 3. Apply the entitlement with ldid:

ldid -Sent.xml debugserver

Alternative Instructions (64bit compatible)

Alternatively if you are on a mac with xcode installed you can follow Peter Steinberger's instructions to add entitlement's to the debugserver that comes with xcode. This will allow you to keep it as a fat binary, which will work on all devices including 64bit iPhone 5S.

You can find Peter's full slides here: https://speakerd.s3.amazonaws.com/presentations/43ca7dd05d120131795d129291fe58eb/Taking_Advantage_of_the_Runtime.pdf and https://speakerdeck.com/steipete/taking-advantage-of-the-runtime which contain more useful tips. Instructions for getting the debugserver to work start on slide 45.

I am not sure if you need an Apple developer membership and certificate to add the entitlements. If this fails for you, try the first method above.

• 1. Mount xcode's developer disk image on your Mac and copy the debugserver binary to your working directory:

hdiutil attach /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/ DeviceSupport/7.0.3\ \(11B508\)/DeveloperDiskImage.dmg
cp /Volumes/DeveloperDiskImage/usr/bin/debugserver .

• 2. Save for following as entitlements.plist:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/ PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>com.apple.springboard.debugapplications</key> <true/>
	<key>run-unsigned-code</key>
	<true/>
	<key>get-task-allow</key> <true/> <key>task_for_pid-allow</key> <true/>
</dict> 
</plist>

• 3. Apply the entitlement with codesign:

codesign -s - --entitlements entitlements.plist -f debugserver

Example session

• 1. Copy MobileNotes to your Mac, e.g. to /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.sdk/Applications/MobileNotes.app/MobileNotes.
• 2. On the device, type:

~/debugserver -x spring host:6789 /Applications/MobileNotes.app/MobileNotes

This will launch MobileNotes and wait for the remote debugger.

• 3. Launch the debugger and attach it to the remote process:

If using GDB:

• On your Mac, launch /Developer/Platforms/iPhoneOS.platform/Developer/usr/libexec/gdb/gdb-arm-apple-darwin.
• Type the following in gdb:

set shlib-path-substitutions / /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.sdk/
file /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.sdk/Applications/MobileNotes.app/MobileNotes
target remote-macosx 192.168.1.101:6789

where 192.168.1.101 should be replaced by the actual IP address of your device. The remote debug connection is now complete.

If using LLDB:

• On your Mac, launch lldb.
• Type the following in lldb:

platform select remote-ios
process connect connect://192.168.1.101:6789

• 4. Enter c to continue and do whatever you want.

References

• iphone-debugserver project — http://code.google.com/p/iphone-debugserver/