prctl SME flags for gnu arm64.

Author: devnexen

libc-test/build.rs

@@ -3583,6 +3583,8 @@ fn test_linux(target: &str) {
 
             // present in recent kernels only
             "PR_PAC_SET_ENABLED_KEYS" | "PR_PAC_GET_ENABLED_KEYS" => true,
+            // present in recent kernels only
+            "PR_SME_SET_VL" | "PR_SME_GET_VL" | "PR_SME_VL_LEN_MAX" | "PR_SME_SET_VL_INHERIT" | "PR_SEM_SET_VL_ONE_EXEC" => true,
 
             // Added in Linux 5.14
             "FUTEX_LOCK_PI2" => true,

src/unix/linux_like/linux/gnu/b64/aarch64/mod.rs

@@ -590,6 +590,13 @@ pub const PR_PAC_APDAKEY: ::c_ulong = 1 << 2;
 pub const PR_PAC_APDBKEY: ::c_ulong = 1 << 3;
 pub const PR_PAC_APGAKEY: ::c_ulong = 1 << 4;
 
+pub const PR_SME_SET_VL: ::c_int = 63;
+pub const PR_SME_GET_VL: ::c_int = 64;
+pub const PR_SME_VL_LEN_MAX: ::c_int = 0xffff;
+
+pub const PR_SME_SET_VL_INHERIT: ::c_ulong = 1 << 17;
+pub const PR_SME_SET_VL_ONE_EXEC: ::c_ulong = 1 << 18;
+
 // Syscall table
 pub const SYS_io_setup: ::c_long = 0;
 pub const SYS_io_destroy: ::c_long = 1;