Debugging mac os x kernel
Embed Embed this gist in your website. Share Copy sharable link for this gist. Learn more about clone URLs. Download ZIP. Two-box osx kernel debugging. Two-box osx kernel development This is an officially unsupported two-box setup, suitable for real kernel and sometimes kext development. Run the following to change from release to development kernel: NOTE: debug flag 0x pauses bootup until the host debugger attaches Install the same KDK of the target box'es kernel.
This comment has been minimized. Sign in to view. Copy link Quote reply. The neat thing is being able to panic the kernel and inspect variables, memory, etc. Run showlldbtypesummaries to enable type summaries. Then, because this is a page fault, CR2 contains the address which could not be accessed, and the error code describes the reason for the page fault. In this case, it was an attempt to write to memory at 0xdeadbeef that triggered the exception. The kernel and kernel extensions on a running Mac OS X system contain just enough symbolic information to resolve dependencies between them.
Mount the Kernel Debug Kit disk image, and you're ready to go. Your own kernel extensions will already have full line number and function name information provided they were built using Xcode's Debug build configuration. On Mac OS X Generating symbol files is done using the kextload command as illustrated in Listing 4. The -soption specifies the directory where to write the symbol files. The -n option causes kextload to prompt for the load address of each kernel extension and its dependencies. Alternatively, you can use the createsymbolfiles script included as part of each Kernel Debug Kit to simplify symbol file generation as shown in Listing 5.
Note: While it's possible to perform cross-architecture remote kernel debugging, symbol files can only be generated on a system with the same architecture as the panicked system. GNU gdb 6. There is absolutely no warranty for GDB. Type "show warranty" for details. If your project is configured to produce stabs debugging information instead of DWARF, use theadd-symbol-file command instead as shown in Listing 7. Listing 7 Loading the symbol file into GDB when using stabs debugging information. The command set print asm-demangle on is a handy way to do this. Next, for each return address in the backtrace, disassemble the function containing that address using the command disass.
Then locate the function containing the instruction pointed to by the instruction pointer. Since the saved instruction pointer from a page fault generally points to the instruction that generated the exception, the movl instruction at 0xab is the suspect. The instruction attempts to write the value 0x7fff to the address pointed to by EAX.
The panic log shows EAX contains the invalid pointer value 0xdeadbeef, which explains the cause of the page fault exception. This diagnosis is consistent with the earlier result from disassembling the single instruction located at the instruction pointer. Also examine the other disassembled functions, looking for the instruction immediately before the address from the backtrace.
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Note that this instruction should be some form of branch instruction. To understand why, recall that the backtrace is a listing of the return addresses saved prior to executing a function call. If the disassembly shows something other than a branch instruction, this is a clue that you may not have generated your symbol file correctly, or that the operating system or Kernel Debug Kit version does not match the panicked machine. This guideline does not apply to the leaf function which contains the instruction that generated an exception.
Another handy technique is to use the "examine memory as instruction" command to disassemble instructions near the address from the backtrace as in Listing One thing to be aware of when using this technique is that the first few instructions may not be correct because the disassembly is likely to begin in the middle of an instruction. Using the techniques discussed in this technote, it is possible to perform an effective post-mortem analysis of a kernel panic. While the information in a panic dump may have been cryptic at first, it should now be just another debugging tool available to the Mac OS X developer.
The Design and Implementation of the 4. Kernel Extension Programming Topics. Holy cow, it'll take me forever to read this through and actually grasp it fully! Thanks theconnactic for this insightful guide! You need to be a member in order to leave a comment. Sign up for a new account in our community.
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Sign in with Twitter. Posted January 13, What is a Kernel Panic? What Does a Panic Look Like? Share this post Link to post Share on other sites.
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Kernel Extension Concepts: Hello Debugger: Debugging a Device Driver With GDB
Sign In Now. Announcements InsanelyMac Theme Problems with donation. Similar Content. Random Kernel Panic on Mojave A friend helps me built my new iMac Pro couples weeks ago. It's always rebooted by kernel panic when I'm working or even using Chrome. I tired to find some topics help me fix it, but I could't find it.
Thank you for help me or any suggestions. OpenCore Development. This thread is for development only! Hp aynl.
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Hi, i've installed on my pc MacOS Mojave but after installation my pc, sometimes, crash giving kernel panic. Newbie here. Been browsing the forums for a while and trying to setup a Mojave That of which I noticed a panic error whenever I try to run diskutil from single user mode. Now have a Olarila app, just download app and clover folder for your Chipset! If you need DSDT edits Alpha, lvs, Austere.