site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com If the following doesn't work for you, you should write up a bug report: (gdb) b main ... -- Terry Thanks for the detailed reply Terry. How do I get this working? Thanks in advance, Aron-Zvi I'm stepping through gdb with gdb like so: gdb --args ./gdb fooprogram How can I use gdb to step through gdb debugging another process? -- Terry _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... The gdb command itself is a wrapper for /usr/libexec/gdb/*; make sure you are targetting the right binary. I also generally recommend that you default start-with-shell off; there's an historical bug in gdb that may not be fixed in the version you are using/creating where it ptrace's the child, but ends up with the Mach port for the shell instead of the Mach port for the child. This won't cause the symptoms you're claiming here, but it will make it difficult to intercept signals to the child process, since that's done via Mach exception ports, and if they get to ptrace, it's too late, you are going to hit the trampoline in the child whether you want to or not, since a BSD_AST has been raised on the child of the shell at that point. Here's an example; the first gdb is the gdb doing the debugging; the second gdb is the gdb being debugged; the r command passes a parameter as the first argument of the second gdb and starts it running under the second gdb; in this case, /bin/ls; now I am debugging the debugger debugging /bin/ls: # gdb /usr/libexec/gdb/gdb-i386-apple-darwin GNU gdb 6.3.50-20050815 (Apple version gdb-768) (Tue Oct 2 04:11:19 UTC 2007) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-apple-darwin"...Reading symbols for shared libraries .......... done (gdb) r /bin/ls Starting program: /usr/libexec/gdb/gdb-i386-apple-darwin /bin/ls Reading symbols for shared libraries ++++++++ + ......................................................................... done GNU gdb 6.3.50-20050815 (Apple version gdb-768) (Tue Oct 2 04:17:32 UTC 2007) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-apple-darwin"...Reading symbols for shared libraries .... done I suspect that if you can't do this, you haven't properly integrated Apple's changes to gdb into the gdb you are attempting to debug (so it would make sense that you were trying to debug it...). On Jul 8, 2009, at 3:43 AM, Aron-Zvi wrote: I've tried running the entire thing as root by switching with su before running the command. I've even tried logging in as root. gdb --args ./gdb fooprogram as root still results in "Unable to find Mach task port for process-id pid_of_ fooprogram (os/kern) failure (0x5)" in the debugee gdb when attempting to run fooprogram. Once again, this happens in macosx_ptrace_him() after task_for_pid() . On Wed, Jul 8, 2009 at 9:55 AM, Terry Lambert <tlambert@apple.com> wrote: On Jul 7, 2009, at 6:34 PM, Aron-Zvi wrote: Hey guys, I've downloaded and built the most recent gdb available at opensource.apple.com - gdb-966. I'm running OS X Leopard 10.5.7. gdb fails in macosx_ptrace_him() following the task_for_pid() call. task_for_pid() returns 5 which i believe is KERN_FAILURE. The message displayed in the debugger is "Unable to find Mach task port for process-id 8455". When I run just ./gdb fooprogram - everything works fine. gdb's gid is set to procmod. Furthermore, I've even tried running gdb as root with identical results. As a setgid program, you will be unable to debug it unless you run the gdb you are using to debug it as root. This is an intentional security feature in task_for_pid() and in ptrace() to preclude you using the debugger to debug a program with escalated privilege and thus access code, data, or interfaces which you would otherwise not be privileged to access or execute as a privileged user or group. It doesn't matter that the group is the same as gdb itself is running as, what matters is that the credential for that user has been adulterated away from the identity given to the system by DirectoryServices or whatever authentication database you are using to establish the credential in the first place. Credentials are established by escalating privilege, setting up the credential, and dropping privilege. If you run a program that re-escalates privilege, unless it does the little dance to establish its rights to establish a new kernel credential authoritatively, privilege is revoked. In your case, your gdb is only sgid, so it's incapable of obtaining root privilege in order to become an authoritative source of credential information for the kernel. This is also generally why we ask people to rely on login as a gatekeeper, rather than writing their own credential establishing code. This email sent to site_archiver@lists.apple.com