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Andrii Nakryiko 3a59f8bef6 bpf: propagate precision in ALU/ALU64 operations 
[ Upstream commit a3b666bfa9 ]

When processing ALU/ALU64 operations (apart from BPF_MOV, which is
handled correctly already; and BPF_NEG and BPF_END are special and don't
have source register), if destination register is already marked
precise, this causes problem with potentially missing precision tracking
for the source register. E.g., when we have r1 >>= r5 and r1 is marked
precise, but r5 isn't, this will lead to r5 staying as imprecise. This
is due to the precision backtracking logic stopping early when it sees
r1 is already marked precise. If r1 wasn't precise, we'd keep
backtracking and would add r5 to the set of registers that need to be
marked precise. So there is a discrepancy here which can lead to invalid
and incompatible states matched due to lack of precision marking on r5.
If r1 wasn't precise, precision backtracking would correctly mark both
r1 and r5 as precise.

This is simple to fix, though. During the forward instruction simulation
pass, for arithmetic operations of `scalar <op>= scalar` form (where
<op> is ALU or ALU64 operations), if destination register is already
precise, mark source register as precise. This applies only when both
involved registers are SCALARs. `ptr += scalar` and `scalar += ptr`
cases are already handled correctly.

This does have (negative) effect on some selftest programs and few
Cilium programs.  ~/baseline-tmp-results.csv are veristat results with
this patch, while ~/baseline-results.csv is without it. See post
scriptum for instructions on how to make Cilium programs testable with
veristat. Correctness has a price.

$ ./veristat -C -e file,prog,insns,states ~/baseline-results.csv ~/baseline-tmp-results.csv | grep -v '+0'
File                     Program               Total insns (A)  Total insns (B)  Total insns (DIFF)  Total states (A)  Total states (B)  Total states (DIFF)
-----------------------  --------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------
bpf_cubic.bpf.linked1.o  bpf_cubic_cong_avoid              997             1700      +703 (+70.51%)                62                90        +28 (+45.16%)
test_l4lb.bpf.linked1.o  balancer_ingress                 4559             5469      +910 (+19.96%)               118               126          +8 (+6.78%)
-----------------------  --------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------

$ ./veristat -C -e file,prog,verdict,insns,states ~/baseline-results-cilium.csv ~/baseline-tmp-results-cilium.csv | grep -v '+0'
File           Program                         Total insns (A)  Total insns (B)  Total insns (DIFF)  Total states (A)  Total states (B)  Total states (DIFF)
-------------  ------------------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------
bpf_host.o     tail_nodeport_nat_ingress_ipv6             4448             5261      +813 (+18.28%)               234               247         +13 (+5.56%)
bpf_host.o     tail_nodeport_nat_ipv6_egress              3396             3446        +50 (+1.47%)               201               203          +2 (+1.00%)
bpf_lxc.o      tail_nodeport_nat_ingress_ipv6             4448             5261      +813 (+18.28%)               234               247         +13 (+5.56%)
bpf_overlay.o  tail_nodeport_nat_ingress_ipv6             4448             5261      +813 (+18.28%)               234               247         +13 (+5.56%)
bpf_xdp.o      tail_lb_ipv4                              71736            73442      +1706 (+2.38%)              4295              4370         +75 (+1.75%)
-------------  ------------------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------

P.S. To make Cilium ([0]) programs libbpf-compatible and thus
veristat-loadable, apply changes from topmost commit in [1], which does
minimal changes to Cilium source code, mostly around SEC() annotations
and BPF map definitions.

  [0] https://github.com/cilium/cilium/
  [1] https://github.com/anakryiko/cilium/commits/libbpf-friendliness

Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221104163649.121784-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2022-12-31 13:32:08 +01:00
arch MIPS: OCTEON: warn only once if deprecated link status is being used 2022-12-31 13:32:00 +01:00
block block-6.1-2022-11-25 2022-11-25 17:50:57 -08:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto treewide: use get_random_bytes() when possible 2022-10-11 17:42:58 -06:00
Documentation spi: Update reference to struct spi_controller 2022-12-31 13:32:06 +01:00
drivers media: platform: exynos4-is: fix return value check in fimc_md_probe() 2022-12-31 13:32:08 +01:00
fs hfs: Fix OOB Write in hfs_asc2mac 2022-12-31 13:32:00 +01:00
include drm/ttm: fix undefined behavior in bit shift for TTM_TT_FLAG_PRIV_POPULATED 2022-12-31 13:32:06 +01:00
init init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash 2022-11-22 22:42:38 +09:00
io_uring io_uring: Fix a null-ptr-deref in io_tctx_exit_cb() 2022-12-07 06:45:20 -07:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: propagate precision in ALU/ALU64 operations 2022-12-31 13:32:08 +01:00
lib lib/notifier-error-inject: fix error when writing -errno to debugfs file 2022-12-31 13:31:58 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
net soreuseport: Fix socket selection for SO_INCOMING_CPU. 2022-12-31 13:32:04 +01:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples samples/bpf: Fix MAC address swapping in xdp2_kern 2022-12-31 13:32:03 +01:00
scripts - Handle different output of readelf on different distros running 2022-11-27 12:08:17 -08:00
security ima: Handle -ESTALE returned by ima_filter_rule_match() 2022-12-31 13:32:07 +01:00
sound ASoC: Intel: avs: Fix potential RX buffer overflow 2022-12-31 13:32:03 +01:00
tools libbpf: Btf dedup identical struct test needs check for nested structs/arrays 2022-12-31 13:32:04 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt Merge branch 'kvm-dwmw2-fixes' into HEAD 2022-11-23 18:59:45 -05:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.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: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.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 MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
Makefile Linux 6.1.1 2022-12-21 17:48:12 +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.