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Date: Fri, 09 Oct 2009 23:39:48 +0400 From: Michael Tokarev <mjt@....msk.ru> To: Cyrill Gorcunov <gorcunov@...il.com> CC: Kernel Mailing List <linux-kernel@...r.kernel.org>, "Rafael J. Wysocki" <rjw@...k.pl>, Kernel Testers List <kernel-testers@...r.kernel.org>, Sam Ravnborg <sam@...nborg.org>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: wrong final bzImage build (regading #14270) Ok, some more to this. It turns out dash's built-in echo command interprets \nnn octal sequences by default, and there's no way to turn that off. So, for example, sed-zoffset command from arch/x86/boot/Makefile (which includes \1 \2 etc substitutions for sed), when echoed in verbose mode (V=1), produces.. interesting characters (with ascii code 1 and 2). It's not practival to replace V=1's echo with /bin/echo I think. So I'd say it's not a bug in the build system after all, but a bug in dash. Well, at least this expanding-by-default didn't trigger another very-difficult-to-find bug (hopefully), but it has good potential. I'll file a bug report against dash. /mjt > [Michael Tokarev - Fri, Oct 09, 2009 at 06:17:50PM +0400] >> Ok, finally the mystery solved. After a week of >> digging. >> >> The original problem was titled "Cannot boot on >> a PIII Celeron", and Rafael filed a bug #14270 >> for this. >> >> In short, what I observed was that a new kernel >> (2.6.31) fails to boot on a PIII Celeron machine. >> But changing just the CPU to plain PIII and voila, >> it now works. I don't know why it behaved this >> way, but I found where was the problem, finally. >> >> And the problem is in the last stage of build, when >> building the bzImage. >> >> make -f scripts/Makefile.build obj=arch/x86/boot/compressed arch/x86/boot/compressed/vmlinux >> ... >> (cat arch/x86/boot/compressed/vmlinux.bin | lzma -9 && echo -ne \\x38\\xd6\\x37\\x00) > arch/x86/boot/compressed/vmlinux.bin.lzma >> ... >> >> Note the echo command. >> >> Now, Debian switched to dash as /bin/sh. And dash >> does not understand the -e option: >> >> $ dash -c 'echo -ne \\x38\\xd6\\x37\\x00' | od -x >> 0000000 6e2d 2065 785c 3833 785c 3664 785c 3733 >> 0000020 785c 3030 000a >> >> $ bash -c 'echo -ne \\x38\\xd6\\x37\\x00' | od -x >> 0000000 d638 0037 >> >> So the final size (it's the size of uncompressed file) >> becomes incorrect. Here's what mkpiggy outputs for >> this (in arch/x86/boot/compressed/piggy.S): >> >> z_output_len = 170930296 >> >> while it should be >> >> z_output_len = 3659320 >> >> And with the former (wrong, larger) size, the whole >> thing just reboots on a PIII Celeron. I've no idea >> why, but the original problem is here. >> >> The same thing happens with bzip2 algorithm which is >> not new, not only with lzma. >> >> The whole thing looks quite hackish to me, -- mkpiggy >> can know the size from the original image just fine, >> instead of getting it from the end of already compressed >> file. >> >> For now, quick fix is to change echo to printf in there. >> Correct fix is to re-write mkpiggy to look at the >> original file for size (IMHO anyway). >> >> And this is a very good candidate for -stable as well. >> The bug is very difficult to find. And now when more >> and more people who use Debian are switching to dash, >> it will be more common. >> >> Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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