exit_to_user_mode(9)

✨ exit_to_user_mode — the manual page, but make it a vibe ✨

okay bestie, this one's a kernel API manual page (exit_to_user_mode(9)), and it's literally the "last looks in the mirror before you go out" function for the kernel. Let's get into it 💅

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🌸 NAME 🌸

exit_to_user_mode — the fixup-state-when-you're-bouncing-back-to-user-mode situation 🫶

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🦋 SYNOPSIS 🦋

void exit_to_user_mode (void );

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🎀 ARGUMENTS 🎀

• void — no arguments. none. zero. it takes nothing and it's iconic for it ✨

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👑 DESCRIPTION 👑

so here's the tea: syscall/interrupt exit enables interrupts, but the kernel state is interrupts disabled when this gets invoked. and it also tells RCU about it, which is important, don't skip that part 🔥

The steps, in order:

1. Trace interrupts on state 👀
2. Invoke context tracking if enabled to adjust RCU state 🔄
3. Invoke architecture specific last minute exit code, e.g. speculation mitigations, etc.: arch_exit_to_user_mode 🧚
4. Tell lockdep that interrupts are enabled 🔓

You invoke this from architecture specific code when syscall_exit_to_user_mode is not suitable as the last step before returning to userspace.

🚨 okay this part is important, no cap: it must be invoked with interrupts disabled, and the caller must be non-instrumentable. Also the caller has to invoke syscall_exit_to_user_mode_work before this. it's giving strict instructions, so follow them fr fr 😭

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💖 SEE ALSO 💖

• Kernel file ./include/linux/irq-entry-common.h 🍓
• arch_enter_from_user_mode(9), arch_in_rcu_eqs(9), enter_from_user_mode(9), arch_exit_to_user_mode_work(9), arch_exit_to_user_mode_prepare(9), arch_exit_to_user_mode(9), arch_do_signal_or_restart(9), __exit_to_user_mode_prepare(9), syscall_exit_to_user_mode_prepare(9), irqentry_exit_to_user_mode_prepare(9), irqentry_enter_from_user_mode(9), irqentry_exit_to_user_mode(9), struct irqentry_state(9), irqentry_enter_from_kernel_mode(9), irqentry_exit_to_kernel_mode_preempt(9), irqentry_exit_to_kernel_mode_after_preempt(9), irqentry_exit_to_kernel_mode(9), irqentry_enter(9), irqentry_exit(9), irqentry_nmi_enter(9), irqentry_nmi_exit(9) — the whole friend group, honestly 💜

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that's the whole page, bestie 🌈 it's from ./include/linux, dated October 2026, and it's the exit_to_user_mode(9) manual page — mwah, go slay your syscalls 💋👑