084a66e307
The backtrace module is written assuming that the frame pointer is in %ebp. By default, -Os optimization level is used, which enables the gcc option -fomit-frame-pointer. This breaks the backtrace functionality. Enabling this may cause an unnoticeable performance cost and virtually no size increase. The backtrace command on x86_64 and probably i386 is broken due to the above rationale. I've not verified, but presumably the backtrace that used to be printed for an unhandled CPU exception is also broken. Do any distros handle this? Considering that, to my knowledge, no one has complained about this in the over 13 years that -Os has been used, has this code actually been useful? Is it worth disabling -fomit-frame-pointer? Though, I don't see much downside right now in disabling it. Alternatively, we could disable/remove the backtrace code. I think it would be nice to keep it and have it working. Nowadays, presumably QEMU makes the GDB stub rarely used as I imagine most are developing in a virtual machines. Also, the GDB stub does not work in UEFI. So, if anyone is using it on real hardware, they are doing so on pretty old machines. The lack of a GDB stub does not seem to be a pain point because no one has got it working on UEFI. This patch gets the backtrace command working on x86_64-efi in QEMU for me. However, it hangs when run on my laptop. Not sure what's going on there. Signed-off-by: Glenn Washburn <development@efficientek.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'