From 3e9637a893e4462937abca5e5e1ae83c390dac00 Mon Sep 17 00:00:00 2001
From: Felipe Neves <felipe.neves@espressif.com>
Date: Tue, 31 Mar 2020 13:58:02 -0300
Subject: [PATCH] test/shared_stack_printf: improved printf with shared stack
 function test

---
 .../newlib/test/test_shared_stack_printf.c    | 34 ++++++++++++++++---
 .../xtensa/expression_with_stack_xtensa_asm.S | 20 +++++++----
 docs/en/api-reference/system/index.rst        |  2 +-
 3 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/components/newlib/test/test_shared_stack_printf.c b/components/newlib/test/test_shared_stack_printf.c
index 81997a5a9a..f81d27d78d 100644
--- a/components/newlib/test/test_shared_stack_printf.c
+++ b/components/newlib/test/test_shared_stack_printf.c
@@ -8,25 +8,49 @@
 #include "test_utils.h"
 #include "esp_expression_with_stack.h"
 
-//makes sure this is not the task stack...
+#define SHARED_STACK_SIZE 8192
+
+static StackType_t *shared_stack_sp = NULL; 
+
+void external_stack_function(void)
+{
+    printf("Executing this printf from external stack! sp=%p\n", get_sp());
+    shared_stack_sp = (StackType_t *)get_sp();
+}
+
 void another_external_stack_function(void) 
 {
     //We can even use Freertos resources inside of this context.
     vTaskDelay(100);
-    printf("Executing this another printf inside a function with external stack");
+    printf("Done!, sp=%p\n", get_sp());
+    shared_stack_sp = (StackType_t *)get_sp();
 }
 
 TEST_CASE("test printf using shared buffer stack", "[newlib]")
 {
-    portSTACK_TYPE *shared_stack = malloc(8192 * sizeof(portSTACK_TYPE));
+    portSTACK_TYPE *shared_stack = malloc(SHARED_STACK_SIZE);
 
     TEST_ASSERT(shared_stack != NULL);
 
     SemaphoreHandle_t printf_lock = xSemaphoreCreateMutex();
     TEST_ASSERT_NOT_NULL(printf_lock);
 
-    ESP_EXECUTE_EXPRESSION_WITH_STACK(printf_lock, shared_stack,8192,printf("Executing this printf from external stack! \n"));
-    ESP_EXECUTE_EXPRESSION_WITH_STACK(printf_lock, shared_stack,8192,another_external_stack_function()); 
+    esp_execute_shared_stack_function(printf_lock, 
+                                    shared_stack,
+                                    SHARED_STACK_SIZE,
+                                    external_stack_function);
+    
+    TEST_ASSERT(((shared_stack_sp >= shared_stack_sp) && 
+                (shared_stack_sp < (shared_stack + SHARED_STACK_SIZE))));
+    
+    esp_execute_shared_stack_function(printf_lock, 
+                                    shared_stack,
+                                    SHARED_STACK_SIZE,
+                                    another_external_stack_function); 
+    
+    TEST_ASSERT(((shared_stack_sp >= shared_stack_sp) && 
+                (shared_stack_sp < (shared_stack + SHARED_STACK_SIZE))));
+
     vSemaphoreDelete(printf_lock);   
     free(shared_stack);
 }
diff --git a/components/xtensa/expression_with_stack_xtensa_asm.S b/components/xtensa/expression_with_stack_xtensa_asm.S
index b01cc5280d..acd7496f91 100644
--- a/components/xtensa/expression_with_stack_xtensa_asm.S
+++ b/components/xtensa/expression_with_stack_xtensa_asm.S
@@ -45,12 +45,20 @@ esp_switch_stack_enter:
 esp_switch_stack_exit:
 
     #ifndef __XTENSA_CALL0_ABI__
-    entry   sp, 0x10
-
-    l32i a4, a2, 0  /* recover the original task stack */
-    mov a1, a4      /* put it on sp register again */
-    retw
-
+    movi    a0, 0                   /* no need to rotate window, it will be destroyed anyway */
+    movi    a6, shared_stack        
+    l32i    sp, a6, 0               /* load shared stack pointer */
+    movi    a12, shared_stack_callback
+    l32i    a12, a12, 0
+    callx4  a12                     /* call user function */
+    movi    a6, shared_stack_function_done
+    movi    a7, 1       
+    s32i    a7, a6, 0               /* hint the function was finished */
+    movi    a6, shared_stack_env    
+    movi    a7, 0
+    movi    a12, longjmp     
+    callx4  a12                 /* jump to last clean state previously saved */
+    ret
     #else 
     #error "this code is written for Window ABI"
     #endif
diff --git a/docs/en/api-reference/system/index.rst b/docs/en/api-reference/system/index.rst
index 5cd0db3b62..7fd3ea5f16 100644
--- a/docs/en/api-reference/system/index.rst
+++ b/docs/en/api-reference/system/index.rst
@@ -19,7 +19,7 @@ System API
     High Resolution Timer <esp_timer>
     :esp32: Himem (large external SPI RAM) API <himem>
     :esp32: Inter-Processor Call <ipc>
-    Call function with external stack <esp_expression_with_stack>
+    Call function with external stack <esp_function_with_shared_stack>
     Interrupt Allocation <intr_alloc>
     Logging <log>
     Miscellaneous System APIs <system>