hardware support float point (FPU) in this project (STM32F769I-disco_Buildroot) in linux user application

[salara1960]

Good day to all.
This project does not support the FPU hardware module on the ARM.
But I'm trying to use FPU in a user level application written in c under uclinux, for this,
as in HAL stm32f769 : SCB->CPACR |= ((3UL << 102) | (3UL << 112) ); (set CP10 Full Access and set CP11 Full Access),
I wrote a function that I activate in the self-written Linux kernel driver.
This function looks like this:
static void vfp_enable(void *unused)
{
uint32_t ret = 0;

asm volatile("ldr   r1, =0xE000ED88 \n\t"    // CPACR is located at address 0xE000ED88
               "ldr   r0, [r1] \n\t"                             // Read CPACR
               "orr   r0, r0, #0xf << 20 \n\t"          // Set bits 20-23 to enable CP10 and CP11 coprocessors
               "str   r0, [r1] \n\t"                            // Write back the modified value to the CPACR
               "isb \n\t"
               : "=r" (ret) : : "cc");
if (ret == 0xF00000)
printk("[%s] FPU activate OK !\n", __func__);
else
printk("[%s] FPU activate Error !\n", __func__);

}
This function is needed to activate the hardware module of the FPU, since after a processor reset it is in an inactive state.
After kernel loaded i see next message from this function : [vfp_enable] FPU activate OK !
I compile a user-level test application (fpu) with the following options: CFLAGS += -Os -Wall -mtune=cortex-m7 -mthumb -mfpu=fpv5-d16 -mfloat-abi=hard.
uсlibс is built with support for hardware FPU module and toolchain also supports hardware FPU (arm-buildroot-uclinux-uclibcgnueabihf packet).
But after starting application I get exception with kernel panic :
Unhandled exception: IPSR = 00000004 LR = fffffffd
CPU: 0 PID: 55 Comm: fpu Not tainted 4.15.10 #3421
Hardware name: Generic DT based system
PC is at 0x0
LR is at 0xc03e044b
pc : [<00000000>] lr : [] psr: 00000000
sp : c03f3d48 ip : 2f5a5f49 fp : c03edfa4
r10: c03edfa8 r9 : 00000001 r8 : 00000000
r7 : 00000001 r6 : 00000000 r5 : c03f3efc r4 : 00000000
r3 : 0000004e r2 : c03f3f08 r1 : 00000000 r0 : 00000000
xPSR: 00000000
CPU: 0 PID: 55 Comm: fpu Not tainted 4.15.10 #3421
Hardware name: Generic DT based system
[] (unwind_backtrace) from [] (show_stack+0xb/0xc)
[] (show_stack) from [] (__invalid_entry+0x4b/0x4c)

Maybe someone already dealt with this problem and can share their experience?
Thank you in advance.
With my best regards.