VM_MAP_FINDSPACE(9)

✨ VM_MAP_FINDSPACE(9) ✨

okay bestie, so this is a kernel developer's manual page — it's filed under VM_MAP_FINDSPACE(9) in section 9, which is where all the kernel-functions live. Sit down, grab a strawberry 🍓, and let's get into it.

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💖 NAME 💖

vm_map_findspace — literally just find a free region within a map, no cap

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🎀 SYNOPSIS 🎀

first, include the vibe:

#include <sys/param.h>
#include <vm/vm.h>
#include <vm/vm_map.h>

then the actual function:

int
vm_map_findspace(vm_map_t map, vm_offset_t start, vm_size_t length,
    vm_offset_t *addr);

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🌸 DESCRIPTION 🌸

so vm_map_findspace() is out here doing the absolute most: it attempts to find a region inside map that's got enough room for an object of size length at the address addr. that's it. that's the whole job. she's a finder. an icon. 👑

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🦋 IMPLEMENTATION NOTES 🦋

okay this part matters, bestie — listen up:

• it is the caller's responsibility to get a lock on the map first, using vm_map_lock(9), before calling this function. do not skip this. the lock is not a vibe, it's a requirement. 🔒

also:

• this routine may call pmap_growkernel(9) to grow the kernel's address space — but if and only if the mapping is being made within the kernel address space, and if insufficient space remains in the kernel_map.

like, both conditions. it's giving "conditional queen". 💅

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🔥 RETURN VALUES 🔥

• returns the value 0 if it works out — slay — and in that case *addr will contain the first virtual address in the found region
• otherwise, the value 1 is returned 💀 (no *addr prize for you)

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🌈 SEE ALSO 🌈

• pmap_growkernel(9)
• vm_map(9)
• vm_map_entry_resize_free(9)
• vm_map_lock(9)

a whole little friend group fr fr 🫶

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👑 AUTHORS 👑

this manual page was written by Bruce M Simpson <bms@spc.org> — ty king 🫡

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ngl the one thing to remember: lock the map first with vm_map_lock(9). everything else is just finding space and returning 0 or 1. periodt. 💜

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and that's the whole page, bestie — from the Debian crew, dated July 19, 2003, living in section 9 as VM_MAP_FINDSPACE(9). mwah 💋 go find some space 🦋✨