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Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Lots of easy overlapping changes in the confict resolutions here. Signed-off-by: David S. Miller <davem@davemloft.net>
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Original file line number | Diff line number | Diff line change |
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=================== | ||
Speculation Control | ||
=================== | ||
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||
Quite some CPUs have speculation-related misfeatures which are in | ||
fact vulnerabilities causing data leaks in various forms even across | ||
privilege domains. | ||
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||
The kernel provides mitigation for such vulnerabilities in various | ||
forms. Some of these mitigations are compile-time configurable and some | ||
can be supplied on the kernel command line. | ||
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||
There is also a class of mitigations which are very expensive, but they can | ||
be restricted to a certain set of processes or tasks in controlled | ||
environments. The mechanism to control these mitigations is via | ||
:manpage:`prctl(2)`. | ||
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||
There are two prctl options which are related to this: | ||
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* PR_GET_SPECULATION_CTRL | ||
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* PR_SET_SPECULATION_CTRL | ||
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PR_GET_SPECULATION_CTRL | ||
----------------------- | ||
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PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature | ||
which is selected with arg2 of prctl(2). The return value uses bits 0-3 with | ||
the following meaning: | ||
|
||
==== ===================== =================================================== | ||
Bit Define Description | ||
==== ===================== =================================================== | ||
0 PR_SPEC_PRCTL Mitigation can be controlled per task by | ||
PR_SET_SPECULATION_CTRL. | ||
1 PR_SPEC_ENABLE The speculation feature is enabled, mitigation is | ||
disabled. | ||
2 PR_SPEC_DISABLE The speculation feature is disabled, mitigation is | ||
enabled. | ||
3 PR_SPEC_FORCE_DISABLE Same as PR_SPEC_DISABLE, but cannot be undone. A | ||
subsequent prctl(..., PR_SPEC_ENABLE) will fail. | ||
==== ===================== =================================================== | ||
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If all bits are 0 the CPU is not affected by the speculation misfeature. | ||
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If PR_SPEC_PRCTL is set, then the per-task control of the mitigation is | ||
available. If not set, prctl(PR_SET_SPECULATION_CTRL) for the speculation | ||
misfeature will fail. | ||
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PR_SET_SPECULATION_CTRL | ||
----------------------- | ||
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PR_SET_SPECULATION_CTRL allows to control the speculation misfeature, which | ||
is selected by arg2 of :manpage:`prctl(2)` per task. arg3 is used to hand | ||
in the control value, i.e. either PR_SPEC_ENABLE or PR_SPEC_DISABLE or | ||
PR_SPEC_FORCE_DISABLE. | ||
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Common error codes | ||
------------------ | ||
======= ================================================================= | ||
Value Meaning | ||
======= ================================================================= | ||
EINVAL The prctl is not implemented by the architecture or unused | ||
prctl(2) arguments are not 0. | ||
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ENODEV arg2 is selecting a not supported speculation misfeature. | ||
======= ================================================================= | ||
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PR_SET_SPECULATION_CTRL error codes | ||
----------------------------------- | ||
======= ================================================================= | ||
Value Meaning | ||
======= ================================================================= | ||
0 Success | ||
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ERANGE arg3 is incorrect, i.e. it's neither PR_SPEC_ENABLE nor | ||
PR_SPEC_DISABLE nor PR_SPEC_FORCE_DISABLE. | ||
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ENXIO Control of the selected speculation misfeature is not possible. | ||
See PR_GET_SPECULATION_CTRL. | ||
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EPERM Speculation was disabled with PR_SPEC_FORCE_DISABLE and caller | ||
tried to enable it again. | ||
======= ================================================================= | ||
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Speculation misfeature controls | ||
------------------------------- | ||
- PR_SPEC_STORE_BYPASS: Speculative Store Bypass | ||
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Invocations: | ||
* prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, 0, 0, 0); | ||
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE, 0, 0); | ||
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE, 0, 0); | ||
* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_FORCE_DISABLE, 0, 0); |
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