bpf_strcmp(9)

💅 bpf_strcmp(9) — like, the Kernel API Manual page, bestie 🎀

okay so real talk: this is a page from the Kernel API Manual (the bpf_strcmp(9) one, yes ma'am 👑) and it's literally just about comparing two strings. That's it. That's the whole vibe. But it's a BPF kfunc, so there are rules, and we're gonna go through every single one of them together. no skipping. periodt. ✨

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🌸 NAME 🌸

bpf_strcmp — compare two strings 🫶

Like, you give it two strings, it tells you who's winning. Iconic behavior honestly.

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✨ SYNOPSIS ✨

__bpf_kfunc int bpf_strcmp (const char *s1__ign , const char *s2__ign );

That's the whole signature, character for character, don't @ me 💅. Note the __bpf_kfunc — that's the special sauce that makes this a BPF callable kernel function, and the __ign suffixes are just how these args are named, keep them exactly as-is.

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🦋 ARGUMENTS 🦋

• s1__ign — one string. just... a string. the first one. 🌸
• s2__ign — another string. the other one. the rival. the second contender. 🍓

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🔥 RETURN 🔥

This is the part where it gets juicy — the return value is doing the actual storytelling here, so let's go one by one, no cap:

• 0 — the strings are equal 💖 (they're twins, they're matching, they ate)
• -1 — s1__ign is smaller 👑
• 1 — s2__ign is smaller 🌈
• -EFAULT — can't read one of the strings 😭 (like, the string said "no ❤️")
• -E2BIG — one of the strings is too large 💀 (she's doing too much, respectfully)
• -ERANGE — one of the strings is outside of kernel address space 🙈 (wrong neighborhood bestie, she does not live there)

fr fr, clock those negative codes — they're not "smaller than" answers, they're errors. don't be out here reading -EFAULT as "string one wins by a lot." that's not the vibe. 🫶

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💜 SEE ALSO 💜

Everything below lives in the kernel file ./kernel/bpf/helpers.c — go say hi to the whole friend group:

• bpf_obj_new(9), bpf_percpu_obj_new(9), bpf_obj_drop(9), bpf_percpu_obj_drop(9), bpf_refcount_acquire(9)
• bpf_list_push_front(9), bpf_list_push_back(9), bpf_rbtree_add(9)
• bpf_task_acquire(9), bpf_task_release(9), bpf_cgroup_acquire(9), bpf_cgroup_release(9), bpf_cgroup_ancestor(9), bpf_cgroup_from_id(9), bpf_task_under_cgroup(9), bpf_task_get_cgroup1(9), bpf_task_from_pid(9), bpf_task_from_vpid(9)
• bpf_dynptr_slice(9), bpf_dynptr_slice_rdwr(9), bpf_dynptr_copy(9), bpf_dynptr_memset(9)
• bpf_iter_bits_new(9), bpf_iter_bits_next(9), bpf_iter_bits_destroy(9)
• bpf_copy_from_user_str(9), bpf_copy_from_user_task_str(9)
• bpf_strcasecmp(9), bpf_strnchr(9), bpf_strchr(9), bpf_strchrnul(9), bpf_strrchr(9), bpf_strnlen(9), bpf_strlen(9), bpf_strspn(9), bpf_strcspn(9), bpf_strstr(9), bpf_strcasestr(9), bpf_strnstr(9), bpf_strncasestr(9)
• bpf_lookup_user_key(9), bpf_lookup_system_key(9), bpf_key_put(9), bpf_verify_pkcs7_signature(9)
• bpf_task_work_schedule_signal(9), bpf_task_work_schedule_resume(9), bpf_timer_cancel_async(9)

that's forty-something friends and every single one of them made the list, we do not cut people from the list 💅✨

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okay mwah, that's the whole page! 🧚 This little gem comes from the source path ./kernel/bpf and it's dated October 2026, and yes the page footer says bpf_strcmp(9) because we always come back to her. 💖 go compare some strings bestie, ily, bye! 🎀