field. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> --- 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 () -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
