Hello Konrad,
On 05/22/2018 01:21 AM, Konrad Rzeszutek Wilk wrote:
field.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Thanks. I've applied this patch, and done quite a bit of editing
Could you take a look in the Git repo, to check that I did not
make any bad edit, please?
Thanks,
Michael
---
v8: New patch
v9: s/EUCLEAN/EINVAL/
Also add section in PR_SET_SPECULATION_CTRL about arg[4,5] being zero.
v12.1:
s/bits 0-2/bits 0-3/
Add PR_SPEC_FORCE_DISABLE and its EPERM return value.
---
man2/prctl.2 | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 143 insertions(+)
diff --git a/man2/prctl.2 b/man2/prctl.2
index 54764d881..87135a0b3 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -1008,6 +1008,102 @@ the "securebits" flags of the calling thread.
See
.BR capabilities (7).
.TP
+.BR PR_GET_SPECULATION_CTRL
+Returns the state of the speculation misfeature which is selected with
+the value of
+.IR arg2 ,
+which must be
+.B PR_SPEC_STORE_BYPASS.
+Otherwise the call fails with the error
+.BR ENODEV .
+The return value uses bit 0-3 with the following meaning:
+.RS
+.TP
+.BR PR_SPEC_PRCTL
+Mitigation can be controlled per task by
+.B PR_SET_SPECULATION_CTRL
+.TP
+.BR PR_SPEC_ENABLE
+The speculation feature is enabled, mitigation is disabled.
+.TP
+.BR PR_SPEC_DISABLE
+The speculation feature is disabled, mitigation is enabled
+.TP
+.BR PR_SPEC_FORCE_DISABLE
+Same as
+.B PR_SPEC_DISABLE
+but cannot be undone.
+.RE
+.IP
+If all bits are
+.B 0
+then the CPU is not affected by the speculation misfeature.
+.IP
+If
+.B PR_SPEC_PRCTL
+is set, then the per task control of the mitigation is available. If not set,
+.B prctl()
+for the speculation misfeature will fail.
+In the above operation
+.I arg3
+,
+.I arg4,
+and
+.I arg5
+must be specified as 0, otherwise the call fails with the error
+.BR EINVAL.
+.TP
+.BR PR_SET_SPECULATION_CTRL
+Sets the state of the speculation misfeature which is selected with
+the value of
+.IR arg2 ,
+which must be
+.B PR_SPEC_STORE_BYPASS.
+Otherwise the call fails with the error
+.BR ENODEV .
+This control is per task. The
+.IR arg3
+is used to hand in the control value, which can be either:
+.RS
+.TP
+.BR PR_SPEC_ENABLE
+The speculation feature is enabled, mitigation is disabled.
+.TP
+.BR PR_SPEC_DISABLE
+The speculation feature is disabled, mitigation is enabled
+.TP
+.BR PR_SPEC_FORCE_DISABLE
+Same as
+.B PR_SPEC_DISABLE
+but cannot be undone. A subsequent
+.B
+prctl(..., PR_SPEC_ENABLE)
+will fail with
+.BR EPERM.
+.RE
+.IP
+Any other value in
+.IR arg3
+will result in the call failure with the error
+.BR ERANGE .
+Also
+.I arg4,
+and
+.I arg5
+must be specified as 0, otherwise the call fails with ethe rror
+.BR EINVAL.
+.IP
+Furtheremore this speculation feature can also be controlled by the boot-time
+parameter of
+.B
+spec_store_bypass_disable=
+Which could enforce a read-only policy which will result in the call failure
+with the error
+.BR ENXIO .
+Consult the
+.B PR_GET_SPECULATION_CTRL
+for details on the possible enumerations.
+.TP
.BR PR_SET_THP_DISABLE " (since Linux 3.15)"
.\" commit a0715cc22601e8830ace98366c0c2bd8da52af52
Set the state of the "THP disable" flag for the calling thread.
@@ -1501,6 +1597,12 @@ and
.IR arg3
does not specify a valid capability.
.TP
+.B ENODEV
+.I option
+was
+.BR PR_SET_SPECULATION_CTRL
+the kernel or CPU does not support the requested speculation misfeature.
+.TP
.B ENXIO
.I option
was
@@ -1510,6 +1612,15 @@ or
and the kernel or the CPU does not support MPX management.
Check that the kernel and processor have MPX support.
.TP
+.B ENXIO
+.I option
+was
+.BR PR_SET_SPECULATION_CTRL
+implies that the control of the selected speculation misfeature is not possible.
+See
+.BR PR_GET_SPECULATION_CTRL
+for the bit fields to determine which option is available.
+.TP
.B EOPNOTSUPP
.I option
is
@@ -1533,6 +1644,14 @@ or tried to set a flag whose corresponding locked flag was set
.B EPERM
.I option
is
+.BR PR_SET_SPECULATION_CTRL
+wherein the speculation was disabled with
+.B PR_SPEC_FORCE_DISABLE
+and caller tried to enable it again.
+.TP
+.B EPERM
+.I option
+is
.BR PR_SET_KEEPCAPS ,
and the caller's
.B SECBIT_KEEP_CAPS_LOCKED
@@ -1570,6 +1689,30 @@ is not present in the process's permitted and inheritable capability sets,
or the
.B PR_CAP_AMBIENT_LOWER
securebit has been set.
+.TP
+.B ERANGE
+.I option
+was
+.BR PR_SET_SPECULATION_CTRL
+and
+.IR arg3
+is incorrect - neither
+.B PR_SPEC_ENABLE
+nor
+.B PR_SPEC_DISABLE
+nor
+.B PR_SPEC_FORCE_DISABLE
+was choosen
+.TP
+.B EINVAL
+.I option
+was
+.BR PR_GET_SPECULATION_CTRL
+or
+.BR PR_SET_SPECULATION_CTRL
+and unused arguments to
+.B prctl()
+are not 0.
.SH VERSIONS
The
.BR prctl ()
--
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