On Tue 2018-07-31 11:11:53, David Howells wrote: > Pavel Machek <pa...@ucw.cz> wrote: > > > Proposal is "message %s foo %s\0param 1\0param2\0", only strings > > allowed. > > I think that's too strict and you will need to allow integer values, IP > addresses and possibly other things also. It could certainly have a limited > set (e.g. no kernel pointers).
I'd always use strings at kernel->user interface. Yes, we should
support integers and IP addresses in kernel, but I'd convert them to
strings before passing them to userspace.
> You also haven't proposed what you think the internal interface should look
> like.
No, I did not.
> and then the kernel has to render the whole lot into
>
> Another example, in ext4 we have:
>
> printk(KERN_NOTICE "EXT4-fs (%s): last error at time %u: %.*s:%d",
>
> so we could do something like:
>
> infof(fc, "EXT4-fs (%s): last error at time %u: %.*s:%d", ...);
>
> on mount. But the use of "%.*s" is a pain for your interface. We can't pass
> qualifiers like "*" to userspace, so either the caller would have to copy the
> string first or the logging routines would have to edit the format string.
> Though I suppose we could leave the editing to userspace.
I guess internal interface can stay the same, at expense of complexity
in infof function. It would data according to %blablax into string,
then replace %blablax with %s. I guess we can keep infof function
simpler by only allowing certain format specifiers...
Best regards,
Pavel
--
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(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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