Copy function from user space to kernel and execute

Question

First of all, I do it for pleasure, so do not judge me.

What I did was pass the function pointer from user space to the kernel, copy the body of the function using copy_from_user to a static array in the kernel, and start jumping in that array to execute.

in the core:

static char handler_text[PAGE_SIZE] __page_aligned_data;
copy_from_user((void *)handler_text , (const void __user *)my_handler , PAGE_SIZE);
((void (*)())(handler_text))();

in user space, what this function does is very simple, as shown below.

void my_handler(){
volatile unsigned long * p = (volatile unsigned long *)0xF0000c10;
*p = 0x0000000;
}

10000938 <my_handler>: 
10000938:   3d 20 f0 00     lis     r9,-4096 
1000093c:   39 40 00 00     li      r10,0 
10000940:   61 29 0c 10     ori     r9,r9,3088 
10000944:   91 49 00 00     stw     r10,0(r9) 
10000948:   4e 80 00 20     blr 
1000094c:   00 01 88 08     .long 0x18808

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Instruction dump:
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 <3d20f000> 39400000 61290c10 91490000

. -?

Answer 1

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UPDATE:

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Answer 2

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flush_dcache_icache_page(virt_to_page((unsigned long)(handler_text)));

copy_from_user((void *)handler_text , (const void __user *)my_handler , PAGE_SIZE);

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