Messages in this thread | | | Date | Tue, 16 Feb 2021 16:52:39 +0000 | From | Chris Down <> | Subject | Re: output: was: Re: [PATCH v4] printk: Userspace format enumeration support |
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Hey Petr,
Petr Mladek writes: >This produces something like: > >3Warning: unable to open an initial console. >3Failed to execute %s (error %d) >6Kernel memory protection disabled. >3Starting init: %s exists but couldn't execute it (error %d) >6Run %s as init process >7initcall %pS returned %d after %lld usecs >7calling %pS @ %i >2initrd overwritten (0x%08lx < 0x%08lx) - disabling it. > >The loglevel is not well separated. It is neither human readable >nor safe for a machine processing . It works only for single digit. >[...] >It looks in less like: [...]
Hmm, why is it important that debugfs output is human readable? My impression was that it's fine to have machine-readable stuff there.
Re: not being not safe for machine processing because it only works for a single digit, I'm a little confused. KERN_* levels are, as far as I know, only a single byte wide, and we rely on that already (eg. in printk_skip_header()). We also already have precedent for null-separation/control characters in (for example) /proc/pid/cmdline.
What am I missing? :-)
>Well, it still might be non-trivial to find the string in the code >and see what exactly has changed. It might be pretty useful >to mention even the source_file:line, for example: > ><3> init/main.c:1489: Warning: unable to open an initial console.\n ><3> init/main.c:1446: Failed to execute %s (error %d)\n ><6> init/main.c:1398: Kernel memory protection disabled.\n ><3> init/main.c:1366: Starting init: %s exists but couldn't execute it (error %d)\n
Almost certainly a theoretical concern, but I am not a big fan of this format, because it relies on a character (":") which is legal in paths (although as you'd expect, we don't have any cases in the kernel right now). That's one of the reasons why I preferred to use nulls, which can't be in a filename.
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