USTORE(9)

✨ USTORE — storing data in userspace, but make it safe 💅

okay so bestie, welcome to USTORE(9) from the Kernel Developer's Manual 🎀 this is one of those pages you're gonna want to bookmark, because if you're writing kernel code and you need to poke a single little value into userspace memory, this whole family of functions is literally your girl. no cap.

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🌸 NAME 🌸

ustore, ustore_8, ustore_16, ustore_32, ustore_64, ustore_char, ustore_short, ustore_int, ustore_long, ustore_ptr — store data in user-space 💖

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🦋 SYNOPSIS 🦋

first things first, you gotta pull in the header:

#include <sys/systm.h>

and then here's the whole squad, all of them returning int:

int
ustore_8(const uint8_t *uaddr, uint8_t val);

int
ustore_16(const uint16_t *uaddr, uint16_t val);

int
ustore_32(const uint32_t *uaddr, uint32_t val);

int
ustore_64(const uint64_t *uaddr, uint64_t val);

int
ustore_char(const unsigned char *uaddr, unsigned char val);

int
ustore_short(const unsigned short *uaddr, unsigned short val);

int
ustore_int(const unsigned int *uaddr, unsigned int val);

int
ustore_long(const unsigned long *uaddr, unsigned long val);

int
ustore_ptr(const void **uaddr, void *val);

like, pick your size, pick your vibe, they're all right there ✨

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💜 DESCRIPTION 💜

okay so the ustore functions are the way you store a value into single memory cells in user-space. that's the whole thing. in every single one of these, the value val gets stored in the user-space memory location that uaddr points at 🫶

and here's a lil detail you do not wanna miss: ustore_64 is only available on systems employing the ‘LP64’ memory model. how do you check if you're on one of those? test for the presence of the _LP64 C preprocessor macro, bestie. iykyk 🔥

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🎀 RETURN VALUES 🎀

the ustore functions return 0 on success and an error number on failure. that's it, that's the vibe check 💅

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🌈 SEE ALSO 🌈

• copy(9)
• ufetch(9)

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💀 fr fr, don't skip the _LP64 check if you're reaching for ustore_64 — it's not available on every system, and that's just facts.

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and that's the whole page, bestie! 👑 this one's from the Debian folks, dated March 18, 2019 — iconic, honestly. go forth and store your data safely, you main character 🧚💖