hash_sub(9)

🦋 hash_sub(9) — the kernel API manual, but make it make sense

okay so bestie, welcome to hash_sub(9) — yes that's the hash_sub man page from the Kernel API Manual, and yes we're gonna get through it together 💅

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✨ NAME ✨

hash_sub — substracts @b from @a and returns the result 🎀

that's it. that's the whole name section. she's short, she's sweet, she's an icon.

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🌸 SYNOPSIS 🌸

struct ftrace_hash * hash_sub (struct ftrace_hash *a , struct ftrace_hash *b );

literally just look at her. two struct ftrace_hash pointers walk in, one struct ftrace_hash pointer (hopefully) walks out. main character energy fr fr 🫶

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💖 ARGUMENTS 💖

• a — a struct ftrace_hash object. the one being subtracted from, iykyk 👑
• b — a struct ftrace_hash object. the one doing the subtracting 🌈

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🔥 DESCRIPTION 🔥

so what actually happens? it returns a struct ftrace_hash object on success, and NULL on error. that's the whole vibe check — success gets you a shiny hash object, error gets you NULL and honestly? same. 😭

no cap, that's every single thing this page tells us about behavior. don't come for me, I'm just the messenger 💀

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⭐ SEE ALSO ⭐

okay this is the part where the page pops OFF — look at this lineup, it's giving guest list at the most exclusive function ever 🎀

lives in the kernel file ./kernel/trace/ftrace.c, and hangs out with:

• ftrace_lookup_ip(9)
• ftrace_free_filter(9)
• ftrace_hash_move(9)
• ftrace_location_range(9)
• ftrace_location(9)
• ftrace_text_reserved(9)
• ftrace_bug(9)
• ftrace_update_record(9)
• ftrace_test_record(9)
• ftrace_get_addr_new(9)
• ftrace_get_addr_curr(9)
• ftrace_rec_iter_start(9)
• ftrace_rec_iter_next(9)
• ftrace_rec_iter_record(9)
• ftrace_run_stop_machine(9)
• arch_ftrace_update_code(9)
• ftrace_startup_subops(9)
• ftrace_shutdown_subops(9)
• ftrace_regex_open(9)
• allocate_ftrace_func_mapper(9)
• ftrace_func_mapper_find_ip(9)
• ftrace_func_mapper_add_ip(9)
• ftrace_func_mapper_remove_ip(9)
• free_ftrace_func_mapper(9)
• register_ftrace_direct(9)
• unregister_ftrace_direct(9)
• modify_ftrace_direct_nolock(9)
• modify_ftrace_direct(9)
• hash_add(9)
• update_ftrace_direct_add(9)
• update_ftrace_direct_del(9)
• update_ftrace_direct_mod(9)
• ftrace_set_filter_ip(9)
• ftrace_set_filter_ips(9)
• ftrace_ops_set_global_filter(9)
• ftrace_set_filter(9)
• ftrace_set_notrace(9)
• ftrace_set_global_filter(9)
• ftrace_set_global_notrace(9)
• ftrace_ops_get_func(9)
• ftrace_kill(9)
• ftrace_is_dead(9)
• register_ftrace_function(9)
• unregister_ftrace_function(9)
• ftrace_lookup_symbols(9)

like?? forty-something cross-references?? she said "I know everybody and everybody knows me" 💅✨

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friendly reminder bestie: I did not invent a single one of these, they're all straight off the page — go read the actual ones if you need the real tea 🍓

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🧚 cute lil sign-off 🧚

and that's the whole page, bestie! sourced from ./kernel/trace, dated October 2026, and filed under hash_sub(9) — go forth and subtract hashes responsibly 💜🦋