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Linus Torvalds 35a10211de minmax: avoid overly complex min()/max() macro arguments in xen 
[ Upstream commit e8432ac802 ]

We have some very fancy min/max macros that have tons of sanity checking
to warn about mixed signedness etc.

This is all things that a sane compiler should warn about, but there are
no sane compiler interfaces for this, and '-Wsign-compare' is broken [1]
and not useful.

So then we compensate (some would say over-compensate) by doing the
checks manually with some truly horrid macro games.

And no, we can't just use __builtin_types_compatible_p(), because the
whole question of "does it make sense to compare these two values" is a
lot more complicated than that.

For example, it makes a ton of sense to compare unsigned values with
simple constants like "5", even if that is indeed a signed type.  So we
have these very strange macros to try to make sensible type checking
decisions on the arguments to 'min()' and 'max()'.

But that can cause enormous code expansion if the min()/max() macros are
used with complicated expressions, and particularly if you nest these
things so that you get the first big expansion then expanded again.

The xen setup.c file ended up ballooning to over 50MB of preprocessed
noise that takes 15s to compile (obviously depending on the build host),
largely due to one single line.

So let's split that one single line to just be simpler.  I think it ends
up being more legible to humans too at the same time.  Now that single
file compiles in under a second.

Reported-and-reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/all/c83c17bb-be75-4c67-979d-54eee38774c6@lucifer.local/
Link: https://staticthinking.wordpress.com/2023/07/25/wsign-compare-is-garbage/ [1]
Cc: David Laight <David.Laight@aculab.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stable-dep-of: be35d91c88 ("xen: tolerate ACPI NVS memory overlapping with Xen allocated memory")
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-10-04 16:29:13 +02:00
arch minmax: avoid overly complex min()/max() macro arguments in xen 2024-10-04 16:29:13 +02:00
block block: fix potential invalid pointer dereference in blk_add_partition 2024-10-04 16:29:01 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: xor - fix template benchmarking 2024-10-04 16:28:49 +02:00
Documentation ipmi: docs: don't advertise deprecated sysfs entries 2024-10-04 16:29:12 +02:00
drivers ata: libata: Clear DID_TIME_OUT for ATA PT commands with sense data 2024-10-04 16:29:13 +02:00
fs jfs: fix out-of-bounds in dbNextAG() and diAlloc() 2024-10-04 16:29:10 +02:00
include ASoC: tas2781-i2c: Drop weird GPIO code 2024-10-04 16:29:05 +02:00
init rust: fix the default format for CONFIG_{RUSTC,BINDGEN}_VERSION_TEXT 2024-08-29 17:33:29 +02:00
io_uring io_uring/io-wq: inherit cpuset of cgroup in io worker 2024-10-04 16:29:01 +02:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel rcu/nocb: Fix RT throttling hrtimer armed from offline CPU 2024-10-04 16:29:07 +02:00
lib lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc() 2024-09-12 11:11:39 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: avoid leaving partial pfn mappings around in error case 2024-09-18 19:24:07 +02:00
net ipv6: avoid possible NULL deref in rt6_uncached_list_flush_dev() 2024-10-04 16:28:59 +02:00
rust rust: kbuild: fix export of bss symbols 2024-09-12 11:11:32 +02:00
samples bpf: Replace bpf_lpm_trie_key 0-length array with flexible array 2024-08-19 06:04:27 +02:00
scripts scripts: kconfig: merge_config: config files: add a trailing newline 2024-09-18 19:24:05 +02:00
security smack: unix sockets: fix accept()ed socket label 2024-09-12 11:11:29 +02:00
sound ASoC: loongson: fix error release 2024-10-04 16:29:05 +02:00
tools selftests/ftrace: Add required dependency for kprobe tests 2024-10-04 16:29:05 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.53 2024-09-30 16:25:15 +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.