53ed2ac8fc
In an entirely unrelated discussion where I pointed out a stupid thinko of mine, Rasmus piped up and noted that that obvious mistake already existed elsewhere in the kernel tree. An "error pointer" is the negative error value encoded as a pointer, making the whole "return error or valid pointer" use-case simple and straightforward. We use it all over the kernel. But the key here is that errors are _negative_ error numbers, not the horrid UNIX user-level model of "-1 and the value of 'errno'". The Apple mailbox driver used the positive error values, and thus just returned invalid normal pointers instead of actual errors. Of course, the reason nobody ever noticed is that the errors presumably never actually happen, so this is fixing a conceptual bug rather than an actual one. Reported-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk> Link: https://lore.kernel.org/all/5c30afe0-f9fb-45d5-9333-dd914a1ea93a@prevas.dk/ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.