mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-02 14:34:13 -04:00
d6d43a9217
In the second loop of ingenic_pinconf_set(), it annotates the switch
default case as unreachable(). The annotation is technically correct,
because that same case would have resulted in an early function return
in the previous loop.
However, the compiled code is suboptimal. GCC seems to work extra hard
to ensure that the unreachable code path triggers undefined behavior.
The function would fall through to start executing whatever function
happens to be next in the compilation unit.
This is problematic because:
a) it adds unnecessary 'ensure undefined behavior' logic, and
corresponding i-cache footprint; and
b) it's less robust -- if a bug were to be introduced, falling through
to the next function would be catastrophic.
Yet another issue is that, while objtool normally understands
unreachable() annotations, there's one special case where it doesn't:
when the annotation occurs immediately after a 'ret' instruction. That
happens to be the case here because unreachable() is immediately before
the return.
Remove the unreachable() annotation and replace it with a comment. This
simplifies the code generation and changes the unreachable error path to
just silently return instead of corrupting execution.
This fixes the following objtool warning:
drivers/pinctrl/pinctrl-ingenic.o: warning: objtool: ingenic_pinconf_set() falls through to next function ingenic_pinconf_group_set()
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/bc20fdbcb826512cf76b7dfd0972740875931b19.1582212881.git.jpoimboe@redhat.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.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.