Operating Systems - System Call - Mechanism & Modes (User vs Kernel)
Which of the following statements about user mode and kernel mode is INCORRECT?
Which of the following statements about user mode and kernel mode is INCORRECT?
medium🐞 Bug Identification Q14 of Q15
Step-by-Step Solution
Step 1: Review privilege separation
User mode is restricted; kernel mode has full privileges.Step 2: Validate each statement
User mode code cannot directly access kernel memory for protection reasons. is true; user mode cannot access kernel memory. Kernel mode has unrestricted access to all hardware and memory. is true; kernel mode has full access. Mode switches are triggered by traps or interrupts to ensure controlled privilege escalation. is true; traps/interrupts cause mode switches.Step 3: Identify incorrect statement
System calls execute entirely in user mode without switching to kernel mode. is false; system calls require switching to kernel mode to execute privileged operations.Final Answer:
Option D -> Option DQuick Check:
System calls always involve mode switch to kernel [OK]
Quick Trick: System calls require kernel mode execution
Common Mistakes:
MISTAKES- Believing system calls run entirely in user mode
- Confusing hardware interrupts with system calls
- Assuming user mode can access kernel memory
Trap Explanation:
PITFALL- Option C is tempting because user code initiates system calls, but the privileged code runs in kernel mode. Other options correctly describe privilege separation.
Interviewer Note:
CONTEXT- Checks candidate's ability to spot subtle misconceptions about privilege levels and system call execution.
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