Volker Armin Hemmann <volkerar...@googlemail.com> posted 200906301410.28158.volkerar...@googlemail.com, excerpted below, on Tue, 30 Jun 2009 14:10:28 +0200:
> On Dienstag 30 Juni 2009, David Shen wrote: >> Hi, >> >> I setup a gentoo 2008 amd 64 system, and then created my own initramfs >> file. But when the initramfs is processed during boot, I got the >> following message: >> >> exe used greatest stack depth: 6040bytes left mdev ...(similar as >> above) >> lvm ...(similar as above) >> >> The system could boot, but I am afraid I have made something wrong, and >> I have no idea how to troubleshoot this. > > > there is no 'trouble'. You activated a debug feature for devs and now > you get the output. Wit 8 or 16lk stack (I think its 16 for amd64, but > have to check that), 6k left is nothing to worry about. FWIW I think it's 8k stack, since the default is (or was at some point, I've never set it manually and I have this setting) "Warn for stack frames larger than... 2048, and he has 6k left. The setting is CONFIG_FRAME_WARN, and it's a number, not a toggle. However, it says set to 0 for nowarn. Duane's DEBUG_STACK_USAGE is apparently for older kernels (a quick git checkout and kernel config for older kernels says the CONFIG_FRAME_WARN option was added for 2.6.26), as a grep USAGE in the .config turns up no hits at all. (There are three for STACK, two indicating support for STACKTRACE and USER_STACKTRACE, the third for STACKPROTECTOR.) But it would seem the default is or was 2048, thus the warning. But it's interesting I don't seem to see such warnings here, running LVM and RAID-(0/1/6) both. However, I do NOT run an initrd/initramfs. I'm guessing that's what's triggering the stack warning (that's what mdev is, right?, the ramdisk memory device). > Go to the kernel hacking submenu in menuconfig and deactivate (almost) > everything but magic sysrq keys ... FWIW, in addition to Magic SysRq key (and 2048 for the stack frame, which I guess I could 0 out), I have three options near the bottom of the kernel hacking submenu enabled. Two of them aren't going to be of much interest to folks who like to hide their boot messages but they help debug kernels that crash before handing control to init, and are thus very useful for those like me that like to run kernel pre-releases, -rcs and even direct git kernels, who find that they don't boot sometimes, and who file bugs on kernel.org's bugzilla. These are the verbose boot messages and early printk options. The third one (well, actually first, since it's above the other two on the menu) is much more generally useful. Filter access to /dev/mem -- CONFIG_STRICT_DEVMEM. This is useful to have it enabled as there's not a lot that should access that, except debugging. xorg doesn't need it, neither does dosemu, or other "common users of /dev/mem". See the help for it. "If in doubt, say Y." Among other things, that can help prevent buggy drivers scribbling on the wrong memory, and it has some (limited) security value as well. As such, it has been enabled by many of the various security patches, for some time. Again, it should normally be enabled unless you do active kernel debugging that needs access to /dev/mem. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
