SWAPCONTEXT(2)

💖 SWAPCONTEXT(2) 💖

okay bestie, welcome to the Linux 2.6 Programmer's Guide section of the man pages — today we're doing swapcontext(2) and honestly? it's giving "quiet little syscall that's lowkey carrying your whole coroutine situation." ✨

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✨ NAME ✨

swapcontext — swap out old context with new context 🦋

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🎀 SYNOPSIS 🎀

int sys_swapcontext (struct ucontext *old_ctx, struct ucontext *new_ctx,
                     int r5, int r6, int r7, int r8,
                     struct pt_regs *regs);

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💅 DESCRIPTION 💅

so here's the vibe: swapcontext swaps out the context old_ctx with the new context new_ctx. that's it, that's the whole job, she's a one-trick pony and she EATS 💅

now about those little int parameters — r5, r6, r7, r8 — they have no place in the system call functionality. like, they're literally just there. not doing anything. main character energy with zero lines, honestly. 🙈

and then there's regs, which indicates the current user register values from the user stack. she's the one actually holding information, periodt. ⭐

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🌈 RETURN VALUE 🌈

swapcontext returns 0 on success 🎉 — icon behaviour, no notes.

otherwise? she returns one of the errors listed down in the Errors section. so yeah, if you get a nonzero return, go read the next section, bestie, it's right there for you. 😭

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💀 ERRORS 💀

• -EFAULT — swapcontext could not verify that the memory area pointed to by old_ctx or new_ctx was accessible for the operation. basically the kernel looked at your pointer and went "girl, that's not yours." 🫶
• -SIGSEGV — a fault occurred when the context was being copied into the kernel's image of the user's registers. this should only occur in an out-of-memory situation. > ⚠️ heads up: OOM territory, that's the only time this should be showing up, so if you're seeing it and you're not out of memory, that's a whole different conversation.

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🦋 SEE ALSO 🦋

• getcontext(2)
• sigaction(2)
• sigaltstack(2)
• sigprocmask(2)

go read those next, they're the rest of the squad 💜

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👑 AUTHOR 👑

Niki Rahimi — thank you for your service, legend 🫡💖

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and that's the whole page, bestie!! this one's from the Linux 2.6 days, dated 2004-March-12 🌸 so yeah she's an elder but she's still iconic and we respect her. mwah, go swap some contexts responsibly 💅✨🎀