csum_and_copy_from_user(9)

🦋 csum_and_copy_from_user(9) 🦋

okay so bestie, welcome to the Kernel API Manual corner where we make kernel functions make sense. This one is literally about copying from user space and checksumming at the same time — main character energy fr fr. 💖

✨ NAME ✨

csum_and_copy_from_user — copy and checksum from user space. 🫶

💅 SYNOPSIS 💅

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

🎀 ARGUMENTS 🎀

• src — source address (user space) 🌸
• dst — destination address 🎀
• len — number of bytes to be copied. 🍓

🌸 DESCRIPTION 🌸

Okay so here's the vibe: it returns an 32bit unfolded checksum of the buffer. ✨

And the tea is that src and dst are best aligned to 64bits. 💅

🔥 SEE ALSO 🔥

• Kernel file ./arch/x86/lib/csum-wrappers_64.c — yes, that exact path, iykyk. 🦋
• csum_and_copy_to_user(9) 👑
• csum_partial_copy_nocheck(9) ⭐

mwah 💋 — this page is signed off from ./arch/x86/lib, dated October 2026, and it's giving "kernel API but make it cute." 🌈💖