STRUCT KLP_FUNC(9)

✨ struct klp_func — function structure for live patching ✨

okay bestie, welcome to the struct klp_func(9) page 💅 this is the kernel API manual, and this little struct is literally the main character of live patching. no cap, it's giving legend behaviour.

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🌸 SYNOPSIS 🌸

struct klp_func {
    const char *old_name;
    void *new_func;
    unsigned long old_sympos;
    void *old_func;
    struct kobject kobj;
    struct list_head node;
    struct list_head stack_node;
    unsigned long old_size, new_size;
    bool nop;
    bool patched;
    bool transition;
 };

copy it exactly, don't be weird about the spacing 💖

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🎀 Members 🎀

• old_name — the name of the function that's getting patched, like the name tag at the party 🫶
• new_func — pointer to the patched function code, aka the glow-up version
• old_sympos — a hint telling you which symbol position the old function can be found in (optional, so no pressure) 🔍
• old_func — pointer to the function actually being patched
• kobj — kobject for sysfs resources, its whole little sysfs situation
• node — list node for klp_object func_list
• stack_node — list node for klp_ops func_stack list
• old_size — size of the old function
• new_size — size of the new function
• nop — temporary patch to use the original code again; dyn. allocated (dynamic, not the nop instruction, don't @ me) 🙈
• patched — the func has been added to the klp_ops list
• transition — the func is currently being applied or reverted

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💜 Description 💜

so the patched and transition variables are the vibe check for the func's patching state ✨ when patching, a func is always in one of these four states, no in-betweens, periodt:

• patched=0 transition=0: unpatched
• patched=0 transition=1: unpatched, temporary starting state
• patched=1 transition=1: patched, may be visible to some tasks
• patched=1 transition=0: patched, visible to all tasks

and when unpatching, it goes in the reverse order, like a rewind 🌀:

• patched=1 transition=0: patched, visible to all tasks
• patched=1 transition=1: patched, may be visible to some tasks
• patched=0 transition=1: unpatched, temporary ending state
• patched=0 transition=0: unpatched

fr fr memorize those two orders — the starting-and-ending temporary states are lowkey the whole point of transition, iykyk 💀

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🌈 SEE ALSO 🌈

• Kernel file ./include/linux/livepatch.h
• struct klp_object(9)
• struct klp_state(9)
• struct klp_patch(9)

go read the whole squad, they're all iconic 👑

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that's the page bestie!! 🎀🦋 from ./include/linux, dated October 2026 — mwah, slay, go patch something 💖✨