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Convert assembly to inline assembly
- See the output in .lst file (with C functions) somehow this does not work very accurately when using .asm files (we cannot see prologue and epilogue sequences for functions written in assembly) - Can see register values with debugging - .asm file can be used to debug step by step (We can set breakpoints in the .asm file)
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2 files changed

+63
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‎Systick_Scheduler/application/CMakeLists.txt

Lines changed: 7 additions & 1 deletion
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@@ -1,6 +1,12 @@
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target_sources(${USER_PROJECT_TARGET} PRIVATE
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osKernel.c
3-
osKernel.S
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# NOTE, if the assembly file below is used, use INLINE_ASSEMBLY=0
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# osKernel.S
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)
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target_compile_definitions(${USER_PROJECT_TARGET} PRIVATE
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# INLINE_ASSEMBLY=0
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INLINE_ASSEMBLY=1
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)
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target_include_directories(${USER_PROJECT_TARGET} PRIVATE
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.

‎Systick_Scheduler/application/osKernel.c

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Original file line numberDiff line numberDiff line change
@@ -88,4 +88,60 @@ static void osKernelStackInit(int thread_number) {
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// xPSR, PC, LR, r12, r3, r2, r1, r0
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// r11, r10, r9, r8, r7, r6, r5, r4
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TCB_STACK[thread_number][STACKSIZE - 1] = 0x01000000;
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// Thread 0 - 100 onwards
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// Thread 1 - 200 onwards
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// Thread 2 - 300 onwards
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// We can see these values when debugging (register view)
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uint32_t tn = thread_number * 100 + 100;
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TCB_STACK[thread_number][STACKSIZE - 4] = tn + 4;
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TCB_STACK[thread_number][STACKSIZE - 5] = tn + 5;
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TCB_STACK[thread_number][STACKSIZE - 6] = tn + 6;
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TCB_STACK[thread_number][STACKSIZE - 7] = tn + 7;
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TCB_STACK[thread_number][STACKSIZE - 8] = tn + 8; // r0
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TCB_STACK[thread_number][STACKSIZE - 9] = tn + 9; // r11
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TCB_STACK[thread_number][STACKSIZE - 10] = tn + 10;
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TCB_STACK[thread_number][STACKSIZE - 11] = tn + 11;
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TCB_STACK[thread_number][STACKSIZE - 12] = tn + 12;
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TCB_STACK[thread_number][STACKSIZE - 13] = tn + 13;
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TCB_STACK[thread_number][STACKSIZE - 14] = tn + 14;
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TCB_STACK[thread_number][STACKSIZE - 15] = tn + 15;
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TCB_STACK[thread_number][STACKSIZE - 16] = tn + 16; // r4
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}
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#if INLINE_ASSEMBLY
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// NOTE, Do not use the __attribute__((naked)) flag for both these functions
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// We want the function to pop their register values and exit (BX LR)
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void SysTick_Handler() {
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__disable_irq();
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__ASM volatile("PUSH {R4-R11}\n"
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"LDR R0,=currentPt\n"
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"LDR R1,[R0]\n"
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"STR SP,[R1]\n"
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"LDR R1, [R1, #4]\n"
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"STR R1, [R0]\n"
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"LDR SP, [R1]\n"
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"POP {R4-R11}\n");
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__enable_irq();
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// NOTE, On exit this function POPs R0-R3 and R12 register
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}
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void osSchedulerLaunch() {
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__ASM volatile("LDR R0,=currentPt\n"
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"LDR R2,[R0]\n"
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"LDR SP,[R2]\n"
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"POP {R4-R11}\n"
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"POP {R0-R3}\n"
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"POP {R12}\n"
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"ADD SP,SP,#4\n"
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"POP {LR}\n"
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"ADD SP,SP,#4\n");
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__enable_irq();
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// NOTE, here we manually pop the registers to initially load the values from
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// the thread stack
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}
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#endif

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