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Borislav Petkov (AMD) 49ce8b6297 kbuild: Disable KCSAN for autogenerated *.mod.c intermediaries 
[ Upstream commit 54babdc034 ]

When KCSAN and CONSTRUCTORS are enabled, one can trigger the

  "Unpatched return thunk in use. This should not happen!"

catch-all warning.

Usually, when objtool runs on the .o objects, it does generate a section
.return_sites which contains all offsets in the objects to the return
thunks of the functions present there. Those return thunks then get
patched at runtime by the alternatives.

KCSAN and CONSTRUCTORS add this to the object file's .text.startup
section:

  -------------------
  Disassembly of section .text.startup:

  ...

  0000000000000010 <_sub_I_00099_0>:
    10:   f3 0f 1e fa             endbr64
    14:   e8 00 00 00 00          call   19 <_sub_I_00099_0+0x9>
                          15: R_X86_64_PLT32      __tsan_init-0x4
    19:   e9 00 00 00 00          jmp    1e <__UNIQUE_ID___addressable_cryptd_alloc_aead349+0x6>
                          1a: R_X86_64_PLT32      __x86_return_thunk-0x4
  -------------------

which, if it is built as a module goes through the intermediary stage of
creating a <module>.mod.c file which, when translated, receives a second
constructor:

  -------------------
  Disassembly of section .text.startup:

  0000000000000010 <_sub_I_00099_0>:
    10:   f3 0f 1e fa             endbr64
    14:   e8 00 00 00 00          call   19 <_sub_I_00099_0+0x9>
                          15: R_X86_64_PLT32      __tsan_init-0x4
    19:   e9 00 00 00 00          jmp    1e <_sub_I_00099_0+0xe>
                          1a: R_X86_64_PLT32      __x86_return_thunk-0x4

  ...

  0000000000000030 <_sub_I_00099_0>:
    30:   f3 0f 1e fa             endbr64
    34:   e8 00 00 00 00          call   39 <_sub_I_00099_0+0x9>
                          35: R_X86_64_PLT32      __tsan_init-0x4
    39:   e9 00 00 00 00          jmp    3e <__ksymtab_cryptd_alloc_ahash+0x2>
                          3a: R_X86_64_PLT32      __x86_return_thunk-0x4
  -------------------

in the .ko file.

Objtool has run already so that second constructor's return thunk cannot
be added to the .return_sites section and thus the return thunk remains
unpatched and the warning rightfully fires.

Drop KCSAN flags from the mod.c generation stage as those constructors
do not contain data races one would be interested about.

Debugged together with David Kaplan <David.Kaplan@amd.com> and Nikolay
Borisov <nik.borisov@suse.com>.

Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Closes: https://lore.kernel.org/r/0851a207-7143-417e-be31-8bf2b3afb57d@molgen.mpg.de
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de> # Dell XPS 13
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-05-17 12:02:12 +02:00
arch KVM: arm64: vgic-v2: Check for non-NULL vCPU in vgic_v2_parse_attr() 2024-05-17 12:02:08 +02:00
block block: fix q->blkg_list corruption during disk rebind 2024-04-17 11:19:28 +02:00
certs
crypto crypto: jitter - fix CRYPTO_JITTERENTROPY help text 2024-03-26 18:19:52 -04:00
Documentation mm, treewide: introduce NR_PAGE_ORDERS 2024-05-02 16:32:41 +02:00
drivers drm/amdkfd: range check cp bad op exception interrupts 2024-05-17 12:02:11 +02:00
fs btrfs: return accurate error code on open failure in open_fs_devices() 2024-05-17 12:02:11 +02:00
include drm/amdkfd: range check cp bad op exception interrupts 2024-05-17 12:02:11 +02:00
init rust: make mutually exclusive with CFI_CLANG 2024-05-02 16:32:42 +02:00
io_uring io_uring: Fix io_cqring_wait() not restoring sigmask on get_timespec64() failure 2024-04-27 17:11:30 +02:00
ipc
kernel bpf: Check bloom filter map value size 2024-05-17 12:02:11 +02:00
lib Fix a potential infinite loop in extract_user_to_sg() 2024-05-17 12:02:02 +02:00
LICENSES
mm mm: turn folio_test_hugetlb into a PageType 2024-05-02 16:32:47 +02:00
net net: mark racy access on sk->sk_rcvbuf 2024-05-17 12:02:10 +02:00
rust rust: kernel: require Send for Module implementations 2024-05-17 12:01:56 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:24:47 +01:00
scripts kbuild: Disable KCSAN for autogenerated *.mod.c intermediaries 2024-05-17 12:02:12 +02:00
security selinux: avoid dereference of garbage after mount failure 2024-04-10 16:35:48 +02:00
sound ALSA: hda: intel-sdw-acpi: fix usage of device_get_named_child_node() 2024-05-17 12:02:05 +02:00
tools selftests/ftrace: Fix event filter target_func selection 2024-05-17 12:02:12 +02:00
usr
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:28:18 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
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MAINTAINERS ALSA: scarlett2: Rename scarlett_gen2 to scarlett2 2024-04-27 17:11:36 +02:00
Makefile Linux 6.6.30 2024-05-02 16:32:50 +02:00
README

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.