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authorThomas Gleixner <tglx@linutronix.de>2018-04-29 15:20:11 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-05-03 13:55:50 +0200
commitb617cfc858161140d69cc0b5cc211996b557a1c7 (patch)
tree64803e15cb79a0d535504ea9b873b7846f614c58 /kernel
parent28a2775217b17208811fa43a9e96bd1fdf417b86 (diff)
prctl: Add speculation control prctls
Add two new prctls to control aspects of speculation related vulnerabilites and their mitigations to provide finer grained control over performance impacting mitigations. PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature which is selected with arg2 of prctl(2). The return value uses bit 0-2 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 If all bits are 0 the CPU is not affected by the speculation misfeature. 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. PR_SET_SPECULATION_CTRL allows to control the speculation misfeature, which is selected by arg2 of prctl(2) per task. arg3 is used to hand in the control value, i.e. either PR_SPEC_ENABLE or PR_SPEC_DISABLE. The common return values are: EINVAL prctl is not implemented by the architecture or the unused prctl() arguments are not 0 ENODEV arg2 is selecting a not supported speculation misfeature PR_SET_SPECULATION_CTRL has these additional return values: ERANGE arg3 is incorrect, i.e. it's not either PR_SPEC_ENABLE or PR_SPEC_DISABLE ENXIO prctl control of the selected speculation misfeature is disabled The first supported controlable speculation misfeature is PR_SPEC_STORE_BYPASS. Add the define so this can be shared between architectures. Based on an initial patch from Tim Chen and mostly rewritten. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sys.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index ad692183dfe9..b76dee23bdc9 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -61,6 +61,8 @@
#include <linux/uidgid.h>
#include <linux/cred.h>
+#include <linux/nospec.h>
+
#include <linux/kmsg_dump.h>
/* Move somewhere else to avoid recompiling? */
#include <generated/utsrelease.h>
@@ -2242,6 +2244,16 @@ static int propagate_has_child_subreaper(struct task_struct *p, void *data)
return 1;
}
+int __weak arch_prctl_spec_ctrl_get(unsigned long which)
+{
+ return -EINVAL;
+}
+
+int __weak arch_prctl_spec_ctrl_set(unsigned long which, unsigned long ctrl)
+{
+ return -EINVAL;
+}
+
SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
unsigned long, arg4, unsigned long, arg5)
{
@@ -2450,6 +2462,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_SVE_GET_VL:
error = SVE_GET_VL();
break;
+ case PR_GET_SPECULATION_CTRL:
+ if (arg3 || arg4 || arg5)
+ return -EINVAL;
+ error = arch_prctl_spec_ctrl_get(arg2);
+ break;
+ case PR_SET_SPECULATION_CTRL:
+ if (arg4 || arg5)
+ return -EINVAL;
+ error = arch_prctl_spec_ctrl_set(arg2, arg3);
+ break;
default:
error = -EINVAL;
break;