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Michael Ellerman 40c2bdef81 powerpc/uaccess: Fix build errors seen with GCC 13/14 
commit 2d43cc701b upstream.

Building ppc64le_defconfig with GCC 14 fails with assembler errors:

    CC      fs/readdir.o
  /tmp/ccdQn0mD.s: Assembler messages:
  /tmp/ccdQn0mD.s:212: Error: operand out of domain (18 is not a multiple of 4)
  /tmp/ccdQn0mD.s:226: Error: operand out of domain (18 is not a multiple of 4)
  ... [6 lines]
  /tmp/ccdQn0mD.s:1699: Error: operand out of domain (18 is not a multiple of 4)

A snippet of the asm shows:

  # ../fs/readdir.c:210:         unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
         ld 9,0(29)       # MEM[(u64 *)name_38(D) + _88 * 1], MEM[(u64 *)name_38(D) + _88 * 1]
  # 210 "../fs/readdir.c" 1
         1:      std 9,18(8)     # put_user       # *__pus_addr_52, MEM[(u64 *)name_38(D) + _88 * 1]

The 'std' instruction requires a 4-byte aligned displacement because
it is a DS-form instruction, and as the assembler says, 18 is not a
multiple of 4.

A similar error is seen with GCC 13 and CONFIG_UBSAN_SIGNED_WRAP=y.

The fix is to change the constraint on the memory operand to put_user(),
from "m" which is a general memory reference to "YZ".

The "Z" constraint is documented in the GCC manual PowerPC machine
constraints, and specifies a "memory operand accessed with indexed or
indirect addressing". "Y" is not documented in the manual but specifies
a "memory operand for a DS-form instruction". Using both allows the
compiler to generate a DS-form "std" or X-form "stdx" as appropriate.

The change has to be conditional on CONFIG_PPC_KERNEL_PREFIXED because
the "Y" constraint does not guarantee 4-byte alignment when prefixed
instructions are enabled.

Unfortunately clang doesn't support the "Y" constraint so that has to be
behind an ifdef.

Although the build error is only seen with GCC 13/14, that appears
to just be luck. The constraint has been incorrect since it was first
added.

Fixes: c20beffeec ("powerpc/uaccess: Use flexible addressing with __put_user()/__get_user()")
Cc: stable@vger.kernel.org # v5.10+
Suggested-by: Kewen Lin <linkw@gcc.gnu.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240529123029.146953-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-07-05 09:14:15 +02:00
arch powerpc/uaccess: Fix build errors seen with GCC 13/14 2024-07-05 09:14:15 +02:00
block blk-iocost: avoid out of bounds shift 2024-05-17 11:50:54 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: ecrdsa - Fix module auto-load on add_key 2024-06-16 13:39:58 +02:00
Documentation net: ena: Add dynamic recycling mechanism for rx buffers 2024-06-16 13:39:52 +02:00
drivers scsi: mpt3sas: Avoid test/set_bit() operating in non-allocated memory 2024-07-05 09:14:15 +02:00
fs jfs: xattr: fix buffer overflow for invalid xattr 2024-07-05 09:14:14 +02:00
include cma: factor out minimum alignment requirement 2024-07-05 09:14:13 +02:00
init init/main.c: Fix potential static_command_line memory overflow 2024-04-27 17:05:28 +02:00
io_uring io_uring: fail NOP if non-zero op flags is passed in 2024-06-16 13:39:53 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel cma: factor out minimum alignment requirement 2024-07-05 09:14:13 +02:00
lib mm/slub, kunit: Use inverted data to corrupt kmem cache 2024-06-16 13:39:16 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/cma: drop incorrect alignment check in cma_init_reserved_mem 2024-07-05 09:14:13 +02:00
net skbuff: introduce skb_pull_data 2024-07-05 09:14:11 +02:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:10:01 +02:00
scripts scripts/gdb: fix SB_* constants parsing 2024-06-16 13:39:54 +02:00
security KEYS: trusted: Do not use WARN when encode fails 2024-05-25 16:20:18 +02:00
sound ALSA: timer: Set lower bound of start tick time 2024-06-16 13:39:52 +02:00
tools selftests/mm: compaction_test: fix bogus test success on Aarch64 2024-07-05 09:14:13 +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: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-10 16:18:34 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
Makefile Linux 5.15.161 2024-06-16 13:40:01 +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.