adds other files necessary to build smp library

port/threadx_smp/src/tx_thread_smp_protect.S

@@ -0,0 +1,50 @@
+#include "tx_port.h"
+
+    .section .text
+    .align  2
+
+    .global _tx_thread_smp_protect
+    .type   _tx_thread_smp_protect, @function
+_tx_thread_smp_protect:
+
+    /* Disable interrupts so we don't get preempted.  */
+    csrr    a0, mstatus                               // Pickup current interrupt posture
+    csrci   mstatus, 0x08                             // Lockout interrupts
+
+    /* Pickup the hart ID.  */
+    csrr    t2, mhartid                               // Pickup the current hart ID
+
+    /* Build address to protection structure.  */
+    la      t1, _tx_thread_smp_protection
+
+    /* If this hart already owns protection, just nest the count.  */
+    LWU     t3, 4(t1)                                 // Pickup owning hart
+    beq     t3, t2, _owned                            // Already owned by this hart
+
+    /* Try to get the protection.  */
+    LWU     t4, 0(t1)                                 // Pickup protection flag
+    beqz    t4, _get_protection                       // If clear, try to claim it
+
+    /* Protection is busy. Restore interrupts and retry.  */
+    csrw    mstatus, a0                               // Restore interrupts
+    j       _tx_thread_smp_protect                    // Restart the protection attempt
+
+_get_protection:
+    li      t4, 1                                     // Build lock value
+    amoswap.w.aq t5, t4, (t1)                         // Attempt to get protection
+    bnez    t5, _protection_busy                      // If old value != 0, retry
+
+_got_protection:
+    fence   rw, rw                                    // Ensure lock acquisition is visible
+    sw      t2, 4(t1)                                 // Save owning hart
+
+_owned:
+    LWU     t5, 8(t1)                                 // Pickup ownership count
+    addi    t5, t5, 1                                 // Increment ownership count
+    sw      t5, 8(t1)                                 // Store ownership count
+    fence   rw, rw                                    // Publish owner/count before return
+    ret
+
+_protection_busy:
+    csrw    mstatus, a0                               // Restore interrupts
+    j       _tx_thread_smp_protect                    // Restart the protection attempt