PR_SET_MM_BRK(2const)

💅 PR_SET_MM_BRK — okay bestie, let's talk brk 💅

so this is a page from the Linux man-pages collection — section 2const — and it's literally about how you, a totally normal process, can reach into the kernel and move your own memory map descriptor fields around. iconic behaviour, no cap.

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✨ NAME ✨

PR_SET_MM_BRK — modify kernel memory map descriptor fields 🫶

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📚 LIBRARY 📚

Standard C library (libc, -lc) — yeah, you gotta link it, obviously.

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🎀 SYNOPSIS 🎀

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>

int prctl(PR_SET_MM, PR_SET_MM_BRK, unsigned long addr, 0L, 0L);

look at that. PR_SET_MM as the first arg, PR_SET_MM_BRK as the second, your addr, and then two whole 0Ls just vibing at the end. they're placeholders, bestie, don't worry about them 💀

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🌸 DESCRIPTION 🌸

So. This sets the current brk(2) value. That's the move. That's the whole thing. 💖

And the way that the address has to behave? the requirements for the address are the same as for the PR_SET_MM_START_BRK option. same rules, different field — go read that page if you want the full tea on what addresses are acceptable 🧚

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⭐ RETURN VALUE ⭐

• On success, 0 is returned. slay ✨
• On error, -1 is returned, and errno is set to indicate the error. (so check your errno, that's the whole point of it)

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😭 ERRORS 😭

• EINVAL — addr is greater than TASK_SIZE (the limit on the size of the user address space for this architecture). yes, there's a ceiling. you cannot just keep going up forever, bestie, this is not your situationship 🚩
• EINVAL — addr is less than or equal to the end of the data segment, or specifies a value that would cause the RLIMIT_DATA resource limit to be exceeded. so it's either too low-key-low or it's gonna blow through your data limit. either way: nope 💀

fr fr, both of these are EINVAL. don't go looking for a different errno, there isn't one.

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👑 STANDARDS 👑

Linux. that's it, that's the standard. iykyk 🐧

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🌈 HISTORY 🌈

Linux 3.3. a classic. a vintage. an era 🎀

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🔥 SEE ALSO 🔥

• prctl(2)
• PR_SET_MM(2const)
• PR_SET_MM_START_BRK(2const)

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and that's the whole page, bestie!! this absolute banger of a man page is from Linux man-pages 6.20, dated 2026-02-08, and honestly it ate 💅✨ go move some memory map fields, you main character 🦋💖