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fe83f5eae4
The commit in Fixes started adding INT3 after RETs as a mitigation
against straight-line speculation.
The fastop SETcc implementation in kvm's insn emulator uses macro magic
to generate all possible SETcc functions and to jump to them when
emulating the respective instruction.
However, it hardcodes the size and alignment of those functions to 4: a
three-byte SETcc insn and a single-byte RET. BUT, with SLS, there's an
INT3 that gets slapped after the RET, which brings the whole scheme out
of alignment:
15: 0f 90 c0 seto %al
18: c3 ret
19: cc int3
1a: 0f 1f 00 nopl (%rax)
1d: 0f 91 c0 setno %al
20: c3 ret
21: cc int3
22: 0f 1f 00 nopl (%rax)
25: 0f 92 c0 setb %al
28: c3 ret
29: cc int3
and this explodes like this:
int3: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 2435 Comm: qemu-system-x86 Not tainted 5.17.0-rc8-sls #1
Hardware name: Dell Inc. Precision WorkStation T3400 /0TP412, BIOS A14 04/30/2012
RIP: 0010:setc+0x5/0x8 [kvm]
Code: 00 00 0f 1f 00 0f b6 05 43 24 06 00 c3 cc 0f 1f 80 00 00 00 00 0f 90 c0 c3 cc 0f \
1f 00 0f 91 c0 c3 cc 0f 1f 00 0f 92 c0 c3 cc <0f> 1f 00 0f 93 c0 c3 cc 0f 1f 00 \
0f 94 c0 c3 cc 0f 1f 00 0f 95 c0
Call Trace:
<TASK>
? x86_emulate_insn [kvm]
? x86_emulate_instruction [kvm]
? vmx_handle_exit [kvm_intel]
? kvm_arch_vcpu_ioctl_run [kvm]
? kvm_vcpu_ioctl [kvm]
? __x64_sys_ioctl
? do_syscall_64
? entry_SYSCALL_64_after_hwframe
</TASK>
Raise the alignment value when SLS is enabled and use a macro for that
instead of hard-coding naked numbers.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.