mirror of https://gitee.com/openkylin/linux.git
aee194b14d
This patch fixes an encoding bug in emit_stx for BPF_B when the source
register is BPF_REG_FP.
The current implementation for BPF_STX BPF_B in emit_stx saves one REX
byte when the operands can be encoded using Mod-R/M alone. The lower 8
bits of registers %rax, %rbx, %rcx, and %rdx can be accessed without using
a REX prefix via %al, %bl, %cl, and %dl, respectively. Other registers,
(e.g., %rsi, %rdi, %rbp, %rsp) require a REX prefix to use their 8-bit
equivalents (%sil, %dil, %bpl, %spl).
The current code checks if the source for BPF_STX BPF_B is BPF_REG_1
or BPF_REG_2 (which map to %rdi and %rsi), in which case it emits the
required REX prefix. However, it misses the case when the source is
BPF_REG_FP (mapped to %rbp).
The result is that BPF_STX BPF_B with BPF_REG_FP as the source operand
will read from register %ch instead of the correct %bpl. This patch fixes
the problem by fixing and refactoring the check on which registers need
the extra REX byte. Since no BPF registers map to %rsp, there is no need
to handle %spl.
Fixes:
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|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| 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.