Re: [PATCH] s390: Warn if kernel command line contains non-printable EBCDIC characters

[Ilya Leoshkevich <iii@linux.ibm.com>]

On 8/26/26 15:51, David Laight wrote:
> On Tue, 25 Aug 2026 17:08:08 +0200
> Ilya Leoshkevich <iii@linux.ibm.com> wrote:
> 
>> Users may accidentally add multi-byte UTF-8 characters to zipl.conf
>> parmline, for example, by copying snippets containing non-breaking
>> spaces (\xC2\xA0) from web pages.
>>
>> The kernel will then interpret the entire command line as EBCDIC,
>> making it unusable. Distinguish this situation from the legitimate
>> EBCDIC conversion by looking for non-printable characters and issue
>> a warning.
> 
> Would it be better to check for the entire line being printable ebcdic?
> All of EBCDIC a-zA-Z0-9 have the 0x80 bit set and most of 0x20..0x7f
> are invalid or control characters (or punctuation).
> 
> David

I actually started with that, but this required introducing a new
_ctype-like table (unfortunately it's not as simple as checking a
couple ranges), so I decided against that and took a shortcut via
ASCII.

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