ftrace_set_filter_ip(9)

✨ ftrace_set_filter_ip(9) ✨

okay so this is a page straight out of the Kernel API Manual (section 9, the kernel-functions girlies 🎀) and we're talking about ftrace_set_filter_ip — lowkey the function that lets you point at a function by address and say "yeah, that one, filter on that one bestie." 💅

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💖 NAME 💖

ftrace_set_filter_ip — set a function to filter on in ftrace, but by address 🦋

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🌸 SYNOPSIS 🌸

int ftrace_set_filter_ip (struct ftrace_ops *ops , unsigned long ip ,
       int remove , int reset );

like yes she takes four whole args, she's thorough, we respect her 😌

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🎀 ARGUMENTS 🎀

• ops — the ops you're setting the filter with. the main character of this whole situation 👑
• ip — the address you're adding to (or removing from) the filter, fr fr 📍
• remove — non zero = take the ip out of the filter. bye bestie 👋
• reset — non zero = reset all filters before applying this filter. clean slate energy ✨

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🦋 DESCRIPTION 🦋

So. Filters denote which functions should be enabled when tracing is enabled — that's the whole vibe, that's the assignment 💜

If ip is NULL, it fails to update the filter. like it just doesn't work, that's the rule, no cap 🙈

⚠️ okay this part matters: this can allocate memory, and that memory must be freed before ops can be freed — either by removing each filtered addr one by one, or by using ftrace_free_filter(ops). do not skip this step, i'm literally begging 😭💀

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⭐ SEE ALSO ⭐

Kernel file ./kernel/trace/ftrace.c — and here's the whole friend group, no one left out 🫶:

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), hash_sub(9), update_ftrace_direct_del(9), update_ftrace_direct_mod(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)

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and that's the page!! 🧚 this lil drop is sourced from ./kernel/trace and stamped October 2026 — go forth and filter responsibly, mwah 💖💅