Merge pull request #2 from kendryte/patch/use_global_pointer

Use "__global_pointer$" instead of "_gp"

lds/kendryte.ld

@@ -143,7 +143,7 @@ SECTIONS
      we can shorten the on-disk segment size.  */
   .sdata :
   {
-    _gp = . + 0x800;
+    __global_pointer$ = . + 0x800;
     *(.srodata.cst16) *(.srodata.cst8) *(.srodata.cst4) *(.srodata.cst2) *(.srodata .srodata.*)
     *(.sdata .sdata.* .gnu.linkonce.s.*)
   } > ram : DATA

lib/bsp/crt.S

@@ -112,7 +112,10 @@ _start:
 
 1:
 
-  la gp, _gp
+.option push
+.option norelax
+  la gp, __global_pointer$
+.option pop
   la  tp, _end + 63
   and tp, tp, -64
   csrr a0, mhartid

lib/freertos/portable/port.c

@@ -140,6 +140,9 @@ int vPortSetInterruptMask(void)
  */
 StackType_t* pxPortInitialiseStack(StackType_t* pxTopOfStack, TaskFunction_t pxCode, void* pvParameters)
 {
+    UBaseType_t gp;
+    __asm volatile("mv %0, gp" : "=r"(gp));
+
     /* Simulate the stack frame as it would be created by a context switch
 	interrupt. */
     pxTopOfStack--;
@@ -147,7 +150,9 @@ StackType_t* pxPortInitialiseStack(StackType_t* pxTopOfStack, TaskFunction_t pxC
     pxTopOfStack -= 22;
     *pxTopOfStack = (portSTACK_TYPE)pvParameters; /* Register a0 */
     pxTopOfStack -= 6;
-    pxTopOfStack -= 2;
+    pxTopOfStack--;
+    *pxTopOfStack = gp;
+    pxTopOfStack--;
     *pxTopOfStack = (StackType_t)(pxTopOfStack - 1);
     pxTopOfStack--;
     *pxTopOfStack = (portSTACK_TYPE)prvTaskExitError; /* Register ra */