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Josh Poimboeuf 323deebaa2 pinctrl: ingenic: Improve unreachable code generation
[ Upstream commit d6d43a92172085a2681e06a0d06aac53c7bcdd12 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-22 11:38:27 +02:00
arch x86/msr: Fix wr/rdmsr_safe_regs_on_cpu() prototypes 2021-05-22 11:38:27 +02:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:08:30 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS 2021-05-11 14:04:15 +02:00
Documentation ARM: 9012/1: move device tree mapping out of linear region 2021-05-19 10:08:32 +02:00
drivers pinctrl: ingenic: Improve unreachable code generation 2021-05-22 11:38:27 +02:00
fs f2fs: fix error handling in f2fs_end_enable_verity() 2021-05-19 10:08:32 +02:00
include mm: fix struct page layout on 32-bit systems 2021-05-19 10:08:31 +02:00
init init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM 2021-04-10 13:34:32 +02:00
ipc
kernel kernel: kexec_file: fix error return code of kexec_calculate_store_digests() 2021-05-19 10:08:28 +02:00
lib kobject_uevent: remove warning in init_uevent_argv() 2021-05-19 10:08:33 +02:00
LICENSES
mm mm/hugetlb: fix F_SEAL_FUTURE_WRITE 2021-05-19 10:08:29 +02:00
net netfilter: conntrack: Make global sysctls readonly in non-init netns 2021-05-19 10:08:33 +02:00
samples samples/bpf: Fix broken tracex1 due to kprobe argument change 2021-05-19 10:08:23 +02:00
scripts kconfig: nconf: stop endless search loops 2021-05-19 10:08:23 +02:00
security security: commoncap: fix -Wstringop-overread warning 2021-05-11 14:04:16 +02:00
sound ASoC: rsnd: check all BUSIF status when error 2021-05-19 10:08:33 +02:00
tools selftests: Set CC to clang in lib.mk if LLVM is set 2021-05-19 10:08:22 +02:00
usr
virt KVM: Stop looking for coalesced MMIO zones if the bus is destroyed 2021-05-14 09:44:15 +02:00
.clang-format
.cocciconfig
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Makefile Linux 5.4.120 2021-05-19 10:08:33 +02:00
README

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.