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Eduard Zingerman says:
====================
This patch-set modifies BPF verifier to accept programs that read from
uninitialized stack locations, but only if executed in privileged mode.
This provides significant verification performance gains: 30% to 70% less
processed states for big number of test programs.
The reason for performance gains comes from treating STACK_MISC and
STACK_INVALID as compatible, when cached state is compared to current state
in verifier.c:stacksafe().
The change should not affect safety, because any value read from STACK_MISC
location has full binary range (e.g. 0x00-0xff for byte-sized reads).
Details and measurements are provided in the description for the patch #1.
The change was suggested by Andrii Nakryiko, the initial patch was created
by Alexei Starovoitov. The discussion could be found at [1].
Changes v1 -> v2 (v1 available at [2]):
- Calls to helper functions now convert STACK_INVALID to STACK_MISC
(suggested by Andrii);
- The test case progs/test_global_func10.c is updated to expect new
error message. Before recent commit [3] exact content of error
messages was not verified for this test.
- Replaced incorrect '//'-style comments in test case asm blocks by
'/*...*/'-style comments in order to fix compilation issues;
- Changed the tag from "Suggested-By" to "Co-developed-by" for Alexei
on patch #1, please let me know if this is appropriate use of the tag.
[1] https://lore.kernel.org/bpf/CAADnVQKs2i1iuZ5SUGuJtxWVfGYR9kDgYKhq3rNV+kBLQCu7rA@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20230216183606.2483834-1-eddyz87@gmail.com/
[3] 95ebb37617 ("selftests/bpf: Convert test_global_funcs test to test_loader framework")
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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.