PR_SET_MM_START_STACK(2const)

💖 PR_SET_MM_START_STACK 💖

okay bestie, so this is a page from the Linux man-pages (section 2const, the constant-definition girlies) and it's all about one very specific little knob you can twist in the kernel. buckle up 🎀

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🌸 NAME 🌸

PR_SET_MM_START_STACK — modify kernel memory map descriptor fields ✨

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🫶 LIBRARY 🫶

Standard C library (libc, -lc) 💅

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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_START_STACK, unsigned long addr, 0L, 0L);

so yes, this is not its own function, it's a sub-operation of prctl(2) — you pass PR_SET_MM as the first arg (that's the "we're editing the memory map descriptors" mode 🧚) and PR_SET_MM_START_STACK as the second arg to say which field you're touching. the last three args are literally addr, 0L, 0L. no cap.

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👑 DESCRIPTION 👑

Set the start address of the stack. 📍

and bestie, heads up: the corresponding memory area must be readable and writable. like, that's the vibe check it has to pass. if it can't be read and written, we have a problem 😭

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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. 💀

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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). so, too big for this architecture's address space, and it said no 🙈
• EINVAL — The permissions of the corresponding memory area are not as required. i.e. it wasn't readable and writable like we just talked about. the memory area did NOT serve 💀

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🦋 STANDARDS 🦋

Linux. 🐧 (that's the whole entry, she's lowkey iconic like that)

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⭐ HISTORY ⭐

Linux 3.3. yes she's been around since 3.3, a true elder of the mmap-adjacent ecosystem 👑

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🎀 SEE ALSO 🎀

• prctl(2)
• PR_SET_MM(2const)

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and that's the whole page, bestie!! 💜 this was PR_SET_MM_START_STACK(2const) from the Linux man-pages, version 6.20, dated 2026-02-08 — written down, loved, and explained with maximum enthusiasm. go forth and set your stack start address (readable + writable, always). mwah 💅🌸🫶