No, you have to do PSP before you drop your privileges

Author: thejpster

cortex-m/src/asm.rs

@@ -193,14 +193,14 @@ pub unsafe fn semihosting_syscall(nr: u32, arg: u32) -> u32 {
 ///   program - stack overflows are obviously UB. If your processor supports
 ///   it, you may wish to set the `PSPLIM` register to guard against this.
 #[cfg(cortex_m)]
-#[inline(always)]
+//#[inline(always)]
 pub unsafe fn enter_unprivileged_psp(psp: *const u32, entry: extern "C" fn() -> !) -> ! {
     unsafe {
         core::arch::asm!(
+            "msr     PSP, {psp}",
             "mrs     {tmp}, CONTROL",
             "orrs    {tmp}, {flags}",
             "msr     CONTROL, {tmp}",
-            "msr     PSP, {psp}",
             "isb",
             "bx      {ent}",
             tmp = in(reg) 0,