System call invoked when writing into a heap memory

Question

I know for malloc sbrk is the system call invoked ,Similarly What is the system cal invoked when i write to a malloed memory(heap memory)

int main

{

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Answer 1

"operating system doesn't see every write that occurs: a write to memory corresponds simply to a STORE assembly instruction, not a system call. It is the hardware that takes care of the STORE and the necessary address translation. The only time the OS will see a memory write is when the address translation in the page tables fails, causing a trap to the OS. "

Please read the below link for details

http://pages.cs.wisc.edu/~dusseau/Classes/CS537-F04/Questions/sol12.html