bpf_copy_from_user_task_str(9)

💅 bpf_copy_from_user_task_str — Kernel API Manual, bestie edition 🎀

okay so this is the bpf_copy_from_user_task_str(9) page, and honestly? it's giving "small function, big responsibility" energy. stick with me and you'll get it ✨

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🌸 NAME 🌸

bpf_copy_from_user_task_str — literally just copy a string out of a task's address space, no cap 🫶

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✨ SYNOPSIS ✨

__bpf_kfunc int bpf_copy_from_user_task_str (void *dst , u32 dst__sz ,
       const void __user *unsafe_ptr__ign , struct task_struct *tsk , u64 flags
       );

look at her, five whole parameters, standing there being iconic 💅

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🦋 ARGUMENTS 🦋

• dst — the destination address, and it lives in kernel space babe. this buffer has to be at least dst__sz bytes long, so no funny business with tiny buffers, ok? 🙈
• dst__sz — the max number of bytes to copy, and yes that count includes the trailing NUL. inclusive queen 🎀
• unsafe_ptr__ign — the source address, sitting all the way over in the task's address space. the name has unsafe in it so you already know 🫶
• tsk — the task whose address space is getting borrowed for this little operation 👑
• flags — and the only supported flag is BPF_F_PAD_ZEROS. that's it. that's the whole menu, periodt 💀

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💖 DESCRIPTION 💖

so what she actually does: copies a NUL-terminated string from a task's address space into the dst__sz buffer. super straightforward, main character behavior 🌟

if the user string is too long, she still makes sure there's a zero terminator inside the dst__sz buffer — the one exception is when the buffer size is 0. zero-size buffer, zero promises, that's the deal 😭

and if the BPF_F_PAD_ZEROS flag is set? two very specific moods:

• on success: memset the tail of dst__sz to 0 💖
• on failure: memset all of dst__sz to 0 💀

she's thorough like that 🧚

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🌈 RETURN 🌈

• success → the number of copied bytes, and yes it includes the NUL terminator ⭐
• failure → a negative error code 😭

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🔥 SEE ALSO 🔥

she runs with a whole squad — ngl this list is long and every single one of them made it:

Kernel file ./kernel/bpf/helpers.c, plus:

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_strcmp(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)

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ok that's the whole page bestie, go forth and copy those strings responsibly 💜

mwah 💋 — this one came from ./kernel/bpf, dated October 2026, and she's filed under bpf_copy_from_user_task_str(9) in case you need to find her again 🎀