Is the kernel stack a different structure to the user-mode stack that is used by applications we (programmers) write?
Can you explain the differences?
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Is the kernel stack a different structure to the user-mode stack that is used by applications we (programmers) write?
Can you explain the differences?
Conceptually, both are the same data structure: a stack.
The reason why there are two different stack per thread is because in user mode, code must not be allowed to mess up kernel memory. When switching to kernel mode, a different stack in memory only accessible in kernel mode is used for return addresses an so on.
If the user mode had access to the kernel stack, it could modify a jump address (for instance), then do a system call; when the kernel jumps to the previously modified address, your code is executed in kernel mode!
Also, security-related information/information about other processes (for synchronisation) might be on the kernel stack, so the user mode should not have read access to it either.