On Wed, Jan 26, 2005 at 08:45:23PM -0600, Colin Watson wrote: > On Wed, Jan 26, 2005 at 05:49:31AM -0600, Colin Watson wrote: > > I had the exact same problem (on Ubuntu rather than Debian, but hey). > > Debugging-by-printf revealed that grub segfaulted after calling > > stage2/builtins.c:disk_read_savesect_func() through the disk_read_func > > pointer in stage2/disk_io.c:rawread(); output from a printf before that > > call was printed, while output from a printf at the beginning of the > > disk_read_savesect_func() call was not printed. It *looks* like the text > > of that function is corrupt in memory, although I'm not wholly convinced > > that my debugging techniques were sound there because I'm having trouble > > debugging a 32-bit binary. > > I think this last sentence was indeed bogus. > > Anyway, I've narrowed down the introduction of the problem to somewhere > between 2.6.9-bk1 and 2.6.9-bk2. Suggestions for changesets in there > that could have broken grub would be gratefully appreciated.
Context for LKML and [EMAIL PROTECTED]; grub segfaults when running its 'install' command (via grub-install) on Debian and Ubuntu systems running stock kernels >= 2.6.9-bk2, up to and including 2.6.11-rc2-bk3 (haven't tried 2.6.11-rc2-bk4 yet). grub is a 32-bit binary relying on ia32 emulation. The implementation of the 'install' command in grub uses nested functions, which require a stack trampoline, and therefore the executable-stack bit is set on the binary: $ readelf -l /sbin/grub | grep STACK STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RWE 0x4 However, booting with noexec=off cures the problem, so it would appear that the executable stack bit isn't being checked properly at least under ia32 emulation. 2.6.9-bk1 works fine, but noexec=on only became the default in 2.6.9-bk2; I haven't yet tried booting 2.6.9-bk1 with noexec=on, but I can try that if it might be helpful. Thanks, -- Colin Watson [EMAIL PROTECTED] - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
