ksize(9)

💅 ksize(9) — like, the kernel API manual bestie 🎀

okay so this is ksize, page 9 of the Kernel API Manual, and no cap it's a tiny little function with a big ol' personality. let's get into it ✨

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🌸 NAME 🌸

ksize — Report full size of underlying allocation 💖

like literally it tells you how much memory is actually chillin' behind that pointer. iconic.

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🦋 SYNOPSIS 🦋

size_t ksize (const void *objp );

that's it. that's the whole vibe check. one argument, one size_t back. slay 💅

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✨ ARGUMENTS ✨

• objp — pointer to the object 🫶 like, the thing you wanna measure. the main character of this whole operation, fr fr.

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🔥 DESCRIPTION 🔥

okay so listen 👑 — this one should only be used internally to query the true size of allocations. that's the whole assignment. that's what it does.

it is not meant to be a way to discover the usable size of an allocation after the fact. so don't be out here using it like a little detective 🕵️‍♀️ — instead, use kmalloc_size_roundup. periodt.

🚨 and this part matters, bestie: using memory beyond the originally requested allocation size may trigger KASAN, UBSAN_BOUNDS, and/or FORTIFY_SOURCE. like do not do that. the vibes will be rancid and the tools will absolutely come for you 💀

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🎀 RETURN 🎀

size of the actual memory used by objp in bytes 💖 that's the number. that's the whole tea. ⭐

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🌈 SEE ALSO 🌈

the friend group 🫶 go say hi:

• Kernel file ./mm/slub.c enum slab_flags(9)
• kmem_cache_alloc_node(9)
• kmem_cache_free(9)
• kfree(9)
• kvfree(9)
• kvfree_atomic(9)
• kvfree_sensitive(9)
• kmem_cache_alloc_bulk(9)

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and that's the page!! 🌸 source is ./mm, dated October 2026, ksize(9) — ily, go free your memory responsibly 🧚‍♀️💜