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POstrerror-like functionality in the kernel?
 

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    <p>Is there any <code>strerror</code>-like functionality currently in the kernel? I haven't been able to find one so my thought is no, but more importantly, has their been any discussion about this? I would think it could reduce troubleshooting time, since you wont have to look up error codes (which not everybody has memorized) and possibly make things a bit easier for system administrators and normal ever-day users (via <code>dmesg</code>).</p> <p>I wanted to ask here before mailing the LKML. My thoughts were for a dual mechanism, one for the error name (e.g., <code>EINVAL</code>) and another for the description. Further, the <code>%m</code> glibc extension could be added to printk, except that it would have to read a error code since the glibc extension reads <code>errno</code>. Perhaps <code>%m</code> could print the error name while <code>%M</code> could print the error description?</p> <p>Anyway, if it is added, it should be a .config option since it will bloat the text size. The size can be shrunk by just storing the error names (1 through 133 currently) in a single string with a null terminator between each string and just a slow <code>strerror</code> (forced to iterate through the string and count null-terminators), since the speed of this shouldn't matter. Internal errors 512-529 would have to be in a separate string. Then, a direct pointer to the null-terminated string could be returned with no need to copy anything. By my calculations, this would take roughly 1322 bytes for the error names and 3540 bytes for the descriptions (based upon what are now in comments after each error's #define and adding "no description" for those that are currently missing one).</p> <p>Then, when config-disabled, the printk <code>%m</code> could just be interpreted as <code>%d</code> and <code>%M</code> could just print nothing (or some such).</p>
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    1. COTry `man strace`. If you are interested in the actual error code, then you have alternate means to display it from user space. Sometime errors are expected such as with `stat`, etc. The kernel is in a position to provide more detailed error information outside the context of an `errno`. These are the things that `dmesg` is made of.
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    2. CO@artless noise thanks for your comment and sorry for the late response. I haven't played with `strace` in a long time and I'd forgotten how useful it is, thanks! For this though, I'm mainly thinking about when you output an error code in a printk. I think I'll put something together and propose it to lkml, but after I'm done with my current project.
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    3. COhmm, I had forgotten about this and I've since written this patch. I had to use `%de` however since using %m broke gcc's printf warnings. :( I guess I should go ahead and submit this. The only thing it currently lacks is that it fails to parse a few things in one arch (I think pa-risc, I forget now).
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