csum_and_copy_to_user(9)

💅 csum_and_copy_to_user — like, the Kernel API Manual page, bestie

okay so this is csum_and_copy_to_user(9) from the Kernel API Manual, and honestly? it's giving "short but mighty." tiny little function, does two whole jobs at once. we love a multitasker. ✨

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🎀 SYNOPSIS

__wsum csum_and_copy_to_user (const void *src , void __user *dst , int len );

look at her. three args, returns a __wsum, no notes. 🫶

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🌸 ARGUMENTS

• src — the source address. where the bytes are coming from, bestie. the origin story. 🌈
• dst — the destination address, and it's user space — capital-U User, so be on your best behaviour. 👑
• len — number of bytes to be copied. that's it, that's the length. int, not negotiable. 📏

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🦋 DESCRIPTION

so basically this returns an 32bit unfolded checksum of the buffer 💖 — copy and checksum in one go, iconique behaviour, no cap.

and a lil' alignment note: src and dst are best aligned to 64bits. that's not a drill, that's just good manners. alignment slay. 💅

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🔥 SEE ALSO

• Kernel file ./arch/x86/lib/csum-wrappers_64.c — go read the source, iykyk 📖
• csum_and_copy_from_user(9) — the other direction, her sister function 🧚
• csum_partial_copy_nocheck(9) — the "no check" girlie, she's got her own vibe 🌸

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fr fr check out that file path, it's literally right there in the arch dir. the receipts are public. 💀

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and that's the whole page, bestie — nothing more to it, she's a short queen. 😭 taken from ./arch/x86/lib, dated October 2026, and that's the vibe check, periodt. 🎀✨🫶