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Alan Maguire e39bce64e5 libbpf: Btf dedup identical struct test needs check for nested structs/arrays 
[ Upstream commit f3c51fe02c ]

When examining module BTF, it is common to see core kernel structures
such as sk_buff, net_device duplicated in the module.  After adding
debug messaging to BTF it turned out that much of the problem
was down to the identical struct test failing during deduplication;
sometimes the compiler adds identical structs.  However
it turns out sometimes that type ids of identical struct members
can also differ, even when the containing structs are still identical.

To take an example, for struct sk_buff, debug messaging revealed
that the identical struct matching was failing for the anon
struct "headers"; specifically for the first field:

__u8       __pkt_type_offset[0]; /*   128     0 */

Looking at the code in BTF deduplication, we have code that guards
against the possibility of identical struct definitions, down to
type ids, and identical array definitions.  However in this case
we have a struct which is being defined twice but does not have
identical type ids since each duplicate struct has separate type
ids for the above array member.   A similar problem (though not
observed) could occur for struct-in-struct.

The solution is to make the "identical struct" test check members
not just for matching ids, but to also check if they in turn are
identical structs or arrays.

The results of doing this are quite dramatic (for some modules
at least); I see the number of type ids drop from around 10000
to just over 1000 in one module for example.

For testing use latest pahole or apply [1], otherwise dedups
can fail for the reasons described there.

Also fix return type of btf_dedup_identical_arrays() as
suggested by Andrii to match boolean return type used
elsewhere.

Fixes: efdd3eb801 ("libbpf: Accommodate DWARF/compiler bug with duplicated structs")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1666622309-22289-1-git-send-email-alan.maguire@oracle.com

[1] https://lore.kernel.org/bpf/1666364523-9648-1-git-send-email-alan.maguire

Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2022-12-31 13:14:07 +01:00
arch MIPS: OCTEON: warn only once if deprecated link status is being used 2022-12-31 13:14:05 +01:00
block block: move CONFIG_BLOCK guard to top Makefile 2022-12-14 11:37:30 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: akcipher - default implementation for setting a private key 2022-10-26 12:35:25 +02:00
Documentation debugfs: fix error when writing negative value to atomic_t debugfs file 2022-12-31 13:14:03 +01:00
drivers media: exynos4-is: don't rely on the v4l2_async_subdev internals 2022-12-31 13:14:07 +01:00
fs hfs: Fix OOB Write in hfs_asc2mac 2022-12-31 13:14:05 +01:00
include soreuseport: Fix socket selection for SO_INCOMING_CPU. 2022-12-31 13:14:07 +01:00
init init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash 2022-12-02 17:41:08 +01:00
io_uring io_uring: Fix a null-ptr-deref in io_tctx_exit_cb() 2022-12-14 11:37:31 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel relay: fix type mismatch when allocating memory in relay_create_buf() 2022-12-31 13:14:05 +01:00
lib lib/notifier-error-inject: fix error when writing -errno to debugfs file 2022-12-31 13:14:03 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/gup: fix gup_pud_range() for dax 2022-12-14 11:37:20 +01:00
net soreuseport: Fix socket selection for SO_INCOMING_CPU. 2022-12-31 13:14:07 +01:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts scripts/faddr2line: Fix regression in name resolution on ppc64le 2022-12-08 11:28:38 +01:00
security capabilities: fix potential memleak on error path from vfs_getxattr_alloc() 2022-11-10 18:15:39 +01:00
sound ASoC: ops: Correct bounds check for second channel on SX controls 2022-12-19 12:36:44 +01:00
tools libbpf: Btf dedup identical struct test needs check for nested structs/arrays 2022-12-31 13:14:07 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt kvm: Add support for arch compat vm ioctls 2022-10-29 10:12:54 +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 futex: Move to kernel/futex/ 2022-12-31 13:14:04 +01:00
Makefile Linux 5.15.85 2022-12-21 17:36:38 +01:00
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.