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Linus Torvalds d40cf34922 gpiolib: acpi: use correct format characters 
[ Upstream commit 213d266ebf ]

When compiling with -Wformat, clang emits the following warning:

  gpiolib-acpi.c:393:4: warning: format specifies type 'unsigned char' but the argument has type 'int' [-Wformat]
                        pin);
                        ^~~

So warning that '%hhX' is paired with an 'int' is all just completely
mindless and wrong. Sadly, I can see a different bogus warning reason
why people would want to use '%02hhX'.

Again, the *sane* thing from a human perspective is to use '%02X. But
if the compiler doesn't do any range analysis at all, it could decide
that "Oh, that print format could need up to 8 bytes of space in the
result". Using '%02hhX' would cut that down to two.

And since we use

        char ev_name[5];

and currently use "_%c%02hhX" as the format string, even a compiler
that doesn't notice that "pin <= 255" test that guards this all will
go "OK, that's at most 4 bytes and the final NUL termination, so it's
fine".

While a compiler - like gcc - that only sees that the original source
of the 'pin' value is a 'unsigned short' array, and then doesn't take
the "pin <= 255" into account, will warn like this:

  gpiolib-acpi.c: In function 'acpi_gpiochip_request_interrupt':
  gpiolib-acpi.c:206:24: warning: '%02X' directive writing between 2 and 4 bytes into a region of size 3 [-Wformat-overflow=]
       sprintf(ev_name, "_%c%02X",
                            ^~~~
  gpiolib-acpi.c:206:20: note: directive argument in the range [0, 65535]

because gcc isn't being very good at that argument range analysis either.

In other words, the original use of 'hhx' was bogus to begin with, and
due to *another* compiler warning being bad, and we had that bad code
being written back in 2016 to work around _that_ compiler warning
(commit e40a3ae1f7: "gpio: acpi: work around false-positive
-Wstring-overflow warning").

Sadly, two different bad compiler warnings together does not make for
one good one.

It just makes for even more pain.

End result: I think the simplest and cleanest option is simply the
proposed change which undoes that '%hhX' change for gcc, and replaces
it with just using a slightly bigger stack allocation. It's not like
a 5-byte allocation is in any way likely to have saved any actual stack,
since all the other variables in that function are 'int' or bigger.

False-positive compiler warnings really do make people write worse
code, and that's a problem. But on a scale of bad code, I feel that
extending the buffer trivially is better than adding a pointless cast
that literally makes no sense.

At least in this case the end result isn't unreadable or buggy. We've
had several cases of bad compiler warnings that caused changes that
were actually horrendously wrong.

Fixes: e40a3ae1f7 ("gpio: acpi: work around false-positive -Wstring-overflow warning")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-20 09:34:10 +02:00
arch cpuidle: PSCI: Move the has_lpi check to the beginning of the function 2022-04-20 09:34:04 +02:00
block block: Fix the maximum minor value is blk_alloc_ext_minor() 2022-04-08 14:24:11 +02:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: xts - Add softdep on ecb 2022-04-08 14:23:55 +02:00
Documentation dt-bindings: net: qcom,ipa: add optional qcom,qmp property 2022-04-20 09:34:04 +02:00
drivers gpiolib: acpi: use correct format characters 2022-04-20 09:34:10 +02:00
fs btrfs: release correct delalloc amount in direct IO write path 2022-04-20 09:34:05 +02:00
include net/sched: flower: fix parsing of ethertype following VLAN header 2022-04-20 09:34:09 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-13 20:59:10 +02:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel stacktrace: move filter_irq_stacks() to kernel/stacktrace.c 2022-04-13 20:59:28 +02:00
lib stacktrace: move filter_irq_stacks() to kernel/stacktrace.c 2022-04-13 20:59:28 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: don't skip swap entry even if zap_details specified 2022-04-13 20:59:27 +02:00
net net/sched: flower: fix parsing of ethertype following VLAN header 2022-04-20 09:34:09 +02:00
samples samples/bpf, xdpsock: Fix race when running for fix duration of time 2022-04-08 14:23:40 +02:00
scripts ubsan: remove CONFIG_UBSAN_OBJECT_SIZE 2022-04-13 20:59:27 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-08 14:23:55 +02:00
sound ALSA: nm256: Don't call card private_free at probe error path 2022-04-20 09:34:09 +02:00
tools selftests: cgroup: Test open-time cgroup namespace usage for migration checks 2022-04-13 20:59:27 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: avoid NULL pointer dereference in kvm_dirty_ring_push 2022-04-13 20:59:26 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: adjust file entry for of_net.c after movement 2022-03-08 19:12:53 +01:00
Makefile Linux 5.15.34 2022-04-13 20:59:28 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.