arm64/sve: Add prctl controls for userspace vector length management
This patch adds two arm64-specific prctls, to permit userspace to
control its vector length:
* PR_SVE_SET_VL: set the thread's SVE vector length and vector
length inheritance mode.
* PR_SVE_GET_VL: get the same information.
Although these prctls resemble instruction set features in the SVE
architecture, they provide additional control: the vector length
inheritance mode is Linux-specific and nothing to do with the
architecture, and the architecture does not permit EL0 to set its
own vector length directly. Both can be used in portable tools
without requiring the use of SVE instructions.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alex Bennée <alex.bennee@linaro.org>
[will: Fixed up prctl constants to avoid clash with PDEATHSIG]
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/kernel/sys.c b/kernel/sys.c
index 9aebc29..c541916 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -110,6 +110,12 @@
#ifndef SET_FP_MODE
# define SET_FP_MODE(a,b) (-EINVAL)
#endif
+#ifndef SVE_SET_VL
+# define SVE_SET_VL(a) (-EINVAL)
+#endif
+#ifndef SVE_GET_VL
+# define SVE_GET_VL() (-EINVAL)
+#endif
/*
* this is where the system-wide overflow UID and GID are defined, for
@@ -2385,6 +2391,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_GET_FP_MODE:
error = GET_FP_MODE(me);
break;
+ case PR_SVE_SET_VL:
+ error = SVE_SET_VL(arg2);
+ break;
+ case PR_SVE_GET_VL:
+ error = SVE_GET_VL();
+ break;
default:
error = -EINVAL;
break;