call_usermodehelper_exec(9)

💜 call_usermodehelper_exec(9) 💜

okay so bestie, welcome to the Kernel API Manual — yes we're in kernel land today, and yes you're gonna slay it, i promise 🫶

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✨ NAME ✨

call_usermodehelper_exec — start a usermode application 🔥

like literally, it kicks off a user-space program from inside the kernel. main character energy fr.

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🌸 SYNOPSIS 🌸

int call_usermodehelper_exec (struct subprocess_info *sub_info , int wait );

that's the whole vibe. one function, two args, zero drama (until the helper doesn't run, but we'll get there 🙈).

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🎀 ARGUMENTS 🎀

• sub_info — all the info about the subprocess, like its little profile card 📋
• wait — whether to wait for the application to finish and return status. when it's UMH_NO_WAIT you don't wait at all — but heads up bestie, you get no useful error back when the program couldn't be exec'ed 😭. the upside? that's what makes it safe to call from interrupt context ⚡

no cap, if you need to know whether the exec actually worked, UMH_NO_WAIT is not the vibe.

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💅 DESCRIPTION 💅

It runs a user-space application. periodt.

The application is started asynchronously if wait is not set, and it runs as a child of system workqueues 🧚 — ie. it runs with full root capabilities and optimized affinity 👑. like, it's not just a helper, it's a whole ceo.

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⭐ NOTE ⭐

okay this part is important so listen up 🙈:

a successful return value does not guarantee the helper was called at all.

You also can't rely on sub_info->{init,cleanup} being called even for UMH_WAIT_* wait modes, because STATIC_USERMODEHELPER_PATH="" turns all helpers into a successful no-op 💀

so like. success just means "sure bestie" not "it definitely happened". vibe check accordingly.

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🌈 SEE ALSO 🌈

• Kernel file ./kernel/umh.c 📁
• __usermodehelper_set_disable_depth(9)
• __usermodehelper_disable(9)
• call_usermodehelper_setup(9)
• call_usermodehelper(9)

the whole friend group honestly 🫶

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and that's the page!! source/version is ./kernel, dated October 2026, and the page is call_usermodehelper_exec(9) — mwah, go run some helpers bestie 💖✨🍓