Big problems using DSB, ISB, DMB and SMC mnemonics with armv7 A8 TI Sitara am335x

/*
 *  test.c - Demonstrating the Secure Monitor Calls (SMCs) in am335x TI armv7 A8 architecture.
 */
#include <stdio.h>

static inline void asm_enable_L2_ECC(void) {
	unsigned int reg_value;

	printf("Start\n");
	__asm ("dsb");					// data synchronization barrier operation
	__asm ("isb");					// instruction synchronization barrier operation
	__asm ("dmb");					// data memory barrier operation
	printf("End\n");
}

void main (void) {
	asm_enable_L2_ECC();
}

root@beaglebone:~/projects/LKM/cp15_smc# ./test
Start
End
root@beaglebone:~/projects/LKM/cp15_smc#

/*
 *  cp15_smc.c - Demonstrating the Secure Monitor Calls (SMCs) in am335x TI armv7 A8 architecture.
 */
#include <linux/module.h>	/* Needed by all modules */
#include <linux/kernel.h>	/* Needed for KERN_INFO */
#include <linux/init.h>		/* Needed for the macros */

MODULE_LICENSE("GPL");						///< The license type -- this affects available functionality
MODULE_DESCRIPTION("An armv7 A8 L2 ECC enabling  driver");	///< The description -- see modinfo
MODULE_VERSION("0.01");						///< A version number to inform users

static inline void asm_enable_L2_ECC(void) {
	unsigned int reg_value;

	__asm ("mrc p15, 0, %0, c0, c2, 4" : "=r"(reg_value) );
	printk(KERN_INFO "Instruction Set Attributes Register 4: 0x%08x\n", reg_value);
	if (0x000f0000 & reg_value) {
		printk(KERN_INFO "The processor does support DMB, DSB and ISB instructions\n");
	}
	else {
		printk(KERN_INFO "The processor does NOT support DMB, DSB and ISB instructions\n");
		return;
	}

	__asm ("stmfd	sp!, {r0 - r4}");		// save contextof R0-R4,which secure monitor call may use
	__asm ("mrc	p15, #1, %0, c9, c0, #2" : "=r"(reg_value) );
	printk(KERN_INFO "L2 Cache Auxiliary Control Register 4: 0x%08x\n", reg_value);
	__asm ("mrc	p15, #1, r0, c9, c0, #2");	// Read L2 Cache Auxiliary Control Register into R0
	__asm ("mov	r1, #0");			// Clear R1
	__asm ("eor	r1, r1, r1");			// xor R1, R1 - clear R1
	__asm ("ldr	r1, =#0x10200000");		// enable mask for ECC (set bits 21 and 28 to enable ECC)
//	__asm ("movt	r1, #0x1020");			// enable mask for ECC (set bits 21 and 28 to enable ECC)
	__asm ("orr	r0, r0, r1");			// OR with original register value
	__asm ("ldr	r12, =#0x00000102");		// setup service ID in R12
//	__asm ("movw	r12, #0x0102");			// setup service ID in R12
	__asm ("mcr	p15, #0, r1, c7, c5, #6");	// invalidate entire branch predictor array

	__asm ("dsb");					// data synchronization barrier operation
	__asm ("isb");					// instruction synchronization barrier operation
	__asm ("dmb");					// data memory barrier operation
//	__asm ("smc	#1");				// secure monitor call SMC (previously SMI)

	__asm ("ldmfd	sp!, {r0 - r4}");		// after returning from SMC, restore R0-R4
//	__asm ("mov	pc, lr");			// return: does NOT work as expected, produces kernel panic!
	__asm ("mrc	p15, #1, %0, c9, c0, #2" : "=r"(reg_value) );
	printk(KERN_INFO "L2 Cache Auxiliary Control Register 4: 0x%08x\n", reg_value);

	return;
}

static int __init cp15_smc_init(void) {
	printk(KERN_INFO "cp15_SMC init\n");
	asm_enable_L2_ECC();
	return 0;
}

static void __exit cp15_smc_exit(void) {
	asm_enable_L2_ECC();
	printk(KERN_INFO "cp15_SMC exit\n");
}

module_init(cp15_smc_init);
module_exit(cp15_smc_exit);

root@beaglebone:~/projects/LKM/cp15_smc# make all
make -C /lib/modules/5.0.15-jumpnow/build M=/home/root/projects/LKM/cp15_smc modules
make[1]: Entering directory '/lib/modules/5.0.15-jumpnow/build'
CC [M] /home/root/projects/LKM/cp15_smc/cp15_smc.o
/tmp/ccrM1hRS.s: Assembler messages:
/tmp/ccrM1hRS.s:118: Error: selected processor does not support `dsb' in ARM mode
/tmp/ccrM1hRS.s:122: Error: selected processor does not support `isb' in ARM mode
/tmp/ccrM1hRS.s:126: Error: selected processor does not support `dmb' in ARM mode
/tmp/ccrM1hRS.s:266: Error: selected processor does not support `dsb' in ARM mode
/tmp/ccrM1hRS.s:270: Error: selected processor does not support `isb' in ARM mode
/tmp/ccrM1hRS.s:274: Error: selected processor does not support `dmb' in ARM mode
make[2]: *** [scripts/Makefile.build:283: /home/root/projects/LKM/cp15_smc/cp15_smc.o] Error 1
make[1]: *** [Makefile:1577: _module_/home/root/projects/LKM/cp15_smc] Error 2
make[1]: Leaving directory '/lib/modules/5.0.15-jumpnow/build'
make: *** [Makefile:4: all] Error 2

root@beaglebone:~/projects/LKM/cp15_smc# gcc --version
gcc (GCC) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.