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Andrii Nakryiko 0133c20480 selftests/bpf: Fix strobemeta selftest regression 
After most recent nightly Clang update strobemeta selftests started
failing with the following error (relevant portion of assembly included):

  1624: (85) call bpf_probe_read_user_str#114
  1625: (bf) r1 = r0
  1626: (18) r2 = 0xfffffffe
  1628: (5f) r1 &= r2
  1629: (55) if r1 != 0x0 goto pc+7
  1630: (07) r9 += 104
  1631: (6b) *(u16 *)(r9 +0) = r0
  1632: (67) r0 <<= 32
  1633: (77) r0 >>= 32
  1634: (79) r1 = *(u64 *)(r10 -456)
  1635: (0f) r1 += r0
  1636: (7b) *(u64 *)(r10 -456) = r1
  1637: (79) r1 = *(u64 *)(r10 -368)
  1638: (c5) if r1 s< 0x1 goto pc+778
  1639: (bf) r6 = r8
  1640: (0f) r6 += r7
  1641: (b4) w1 = 0
  1642: (6b) *(u16 *)(r6 +108) = r1
  1643: (79) r3 = *(u64 *)(r10 -352)
  1644: (79) r9 = *(u64 *)(r10 -456)
  1645: (bf) r1 = r9
  1646: (b4) w2 = 1
  1647: (85) call bpf_probe_read_user_str#114

  R1 unbounded memory access, make sure to bounds check any such access

In the above code r0 and r1 are implicitly related. Clang knows that,
but verifier isn't able to infer this relationship.

Yonghong Song narrowed down this "regression" in code generation to
a recent Clang optimization change ([0]), which for BPF target generates
code pattern that BPF verifier can't handle and loses track of register
boundaries.

This patch works around the issue by adding an BPF assembly-based helper
that helps to prove to the verifier that upper bound of the register is
a given constant by controlling the exact share of generated BPF
instruction sequence. This fixes the immediate issue for strobemeta
selftest.

  [0] acabad9ff6

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211029182907.166910-1-andrii@kernel.org
2021-11-01 17:08:21 +01:00
arch riscv, bpf: Add BPF exception tables 2021-10-28 01:02:44 +02:00
block
certs
crypto
Documentation docs/bpf: Update documentation for BTF_KIND_DECL_TAG typedef support 2021-10-22 17:04:44 -07:00
drivers bluetooth-next pull request for net-next: 2021-10-05 07:41:16 -07:00
fs
include bpf: Add bpf_kallsyms_lookup_name helper 2021-10-28 16:30:06 -07:00
init
ipc
kernel bpf: Disallow unprivileged bpf by default 2021-11-01 17:06:47 +01:00
lib bpf, tests: Add module parameter test_suite to test_bpf module 2021-10-28 11:41:16 +02:00
LICENSES
mm
net bpf: Add bpf_skc_to_unix_sock() helper 2021-10-21 15:11:06 -07:00
samples samples: seccomp: Use __BYTE_ORDER__ 2021-10-25 20:39:42 -07:00
scripts bpf: Add bpf_skc_to_unix_sock() helper 2021-10-21 15:11:06 -07:00
security
sound
tools selftests/bpf: Fix strobemeta selftest regression 2021-11-01 17:08:21 +01:00
usr
virt
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MAINTAINERS mips, bpf: Enable eBPF JITs 2021-10-06 12:28:30 -07:00
Makefile
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.