ftrace_func_mapper_find_ip(9)

💅 ftrace_func_mapper_find_ip — from the Kernel API Manual, bestie 🎀

okay so listen. we're in the Kernel API Manual today, and the star of the show is ftrace_func_mapper_find_ip(9). yes it's a long name. no we're not shortening it. it's iconic, it ate, periodt. ✨

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🌸 NAME 🌸

ftrace_func_mapper_find_ip — literally "find some data mapped to an ip". that's the whole vibe. you got an ip, you want the data, this function is your girl. 💖

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✨ SYNOPSIS ✨

void ** ftrace_func_mapper_find_ip (struct ftrace_func_mapper *mapper ,
unsigned long ip );

look at her. two args, one return, zero drama. 🦋

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🎀 ARGUMENTS 🎀

• mapper — the mapper that has the ip maps. she's the one holding all the receipts, okay? the whole map lives with her. 💅
• ip — the instruction pointer to find the data for. like, the actual key you're looking up. give her the ip and she'll go find her matching data. 🔍

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💜 RETURN 💜

so here's the tea ☕ — if it finds the data, you get the data mapped to ip. if not? NULL. that's it, that's the mood. 😭

but wait, there's a plot twist that's lowkey the best part: the return is actually the address of the mapper data pointer. not the data itself, the address of the pointer. and there's a reason for this:

The address is returned for use cases where the data is no bigger than a long, and the user can use the data pointer as its data instead of having to allocate more memory for the reference.

so if your data fits in a long, you don't gotta go allocate a whole extra chunk of memory just to hold a reference. use the pointer itself as the data. efficiency slay. 👑

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🦋 SEE ALSO 🦋

all her friends, fr fr. the Kernel file ./kernel/trace/ftrace.c and honestly the entire extended universe:

• 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_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)
• hash_sub(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, the whole group chat got tagged. 🫶

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and that's the page, bestie!! 🌈 this one comes from ./kernel/trace, dated October 2026, and it's filed under ftrace_func_mapper_find_ip(9) — go off, kernel docs, you ate that. 💀💖 mwah! 🍓🧚