On Fri, Feb 05, 2021 at 10:45:19PM +0000, Chris Down wrote:
Hi Steven,
Steven Rostedt writes:
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Interesting, because when I was looking at the original patch (looked at
the lore link before reading your reply), I thought to myself "this looks
exactly like what I did for trace_printk formats", which the above file is
where it is shown. I'm curious if this work was inspired by that?
The double __builtin_constant_p() trick was suggested by Johannes based on
prior art in trace_puts() just prior to patch submission. Other than that,
it seems we came up with basically the same solution independently. :-)
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Anyway, there is something wrong at the moment. The output looks fine
with cat. But "less" says that it is a binary format and the output
is a bit messy:
Hmm, that's usually the case when lseek gets messed up. Not sure how that
happened.
It looks as intended to me -- none of the newlines, nulls, or other control
sequences are escaped currently, since I didn't immediately see a reason to
do that. If that's a blocker though, I'm happy to change it.
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$> less /proc/printk_formats
"/proc/printk_formats" may be a binary file. See it anyway?
vmlinux,^A3Warning: unable to open an initial console.
^@vmlinux,^A3Failed to execute %s (error %d)
^@vmlinux,^A6Kernel memory protection disabled.
^@vmlinux,^A3Starting init: %s exists but couldn't execute it (error %d)
That is for now. I still have to think about it. And I am also curious
about what others thing about this idea.
I'm not against the idea. I don't think it belongs in /proc. Perhaps
debugfs is a better place to put it.
Any location is fine with me, as long as it gets to userspace. How does
<debugfs>/printk/formats or <debugfs>/printk/formats/<module> sound to you?
That's fine with me, but I'd like to see the patch with this in it first
before approving it :)
thanks,
greg k-h