Re: [PATCH] kbuild: correct size calculation of bzImgae / fix x86 boot

From: Willy Tarreau
Date: Sun Dec 20 2009 - 08:10:23 EST

On Sun, Dec 20, 2009 at 01:47:13PM +0300, Michael Tokarev wrote:
> Willy Tarreau wrote:
> > On Sun, Dec 20, 2009 at 11:03:44AM +0100, Sam Ravnborg wrote:
> >> We use ... printf \x ... when calculating the size of the
> >> compressed kernel.
> >> Unfortunately dash built-in printf does not support this notation
> >> resulting in a non-bootable kernel.
> >>
> >> Fix this by always using the external version of printf.
> >
> > Do we really want to workaround shells bugs ? I mean, either
> There's no bugs in dash, as far as I can see. According to
> POSIX, a) echo does not need to interpret _any_ escape sequences
> at all, and b) printf is not required to interpret \x sequences.


> Ref:
> ...
> string
> A string to be written to standard output. If the first operand is -n,
> or if any of the operands contain a backslash ( '\' ) character,
> the results are implementation-defined.
> [XSI] On XSI-conformant systems, [..] the following character sequences
> shall be recognized on XSI-conformant systems within any of the arguments:
> \a \b \c \f \n \r \t \v \\
> \0num
> Write an 8-bit value that is the zero, one, two, or three-digit octal
> number num.
> In addition to the escape sequences shown in the Base Definitions volume of IEEE
> Std 1003.1-2001, Chapter 5, File Format Notation ( '\\', '\a', '\b', '\f', '\n',
> '\r', '\t', '\v' ), "\ddd", where ddd is a one, two, or three-digit octal number,
> shall be written as a byte with the numeric value specified by the octal number.

OK so the bug will not be fixed by calling /usr/bin/printf. It
will still work by pure luck when a the proper printf utility
will be there, but not when we use a posix-compliant one. The
proper fix then consists in writing octal chars in the form
of "\ddd" instead of "\xhh". And if dash is posix-compliant,
no need for the absolute path.


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