prctl.2: Add PR_SPEC_INDIRECT_BRANCH for SPECULATION_CTRL prctls

Add the PR_SPEC_INDIRECT_BRANCH "misfeature" added in Linux 4.20
for PR_SET_SPECULATION_CTRL and PR_GET_SPECULATION_CTRL.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/prctl.2 b/man2/prctl.2
index 605194fc7ce4d16890f78cc1dee34b536343e3c2..4223d5a9bf9e0908cc2dc5261364941b1a03d813 100644 (file)
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -1213,11 +1213,20 @@ arguments must be specified as 0; otherwise the call fails with the error
 .\" commit 356e4bfff2c5489e016fdb925adbf12a1e3950ee
 Sets the state of the speculation misfeature specified in
 .IR arg2 .
-Currently, the only permitted value for this argument is
+Currently, this argument must be one of:
+.RS
+.TP
 .B PR_SPEC_STORE_BYPASS
-(otherwise the call fails with the error
+speculative store bypass control, or
+.\" commit 9137bb27e60e554dab694eafa4cca241fa3a694f
+.TP
+.BR PR_SPEC_INDIRECT_BRANCH " (since Linux 4.20)"
+indirect branch speculation control.
+.RE
+.IP
+(Otherwise the call fails with the error
 .BR ENODEV ).
-This setting is a per-thread attribute.
+These settings are per-thread attributes.
 The
 .IR arg3
 argument is used to hand in the control value,
@@ -1235,13 +1244,16 @@ Same as
 .BR PR_SPEC_DISABLE ,
 but cannot be undone.
 A subsequent
-.B
-prctl(..., PR_SPEC_ENABLE)
+.BR prctl (\c
+.IR arg2 ,
+.BR PR_SPEC_ENABLE )
+with the same value for
+.I arg2
 will fail with the error
 .BR EPERM .
 .RE
 .IP
-Any other value in
+Any unsupported value in
 .IR arg3
 will result in the call failing with the error
 .BR ERANGE .