xrstors(9)

💖 NAME 💖

Okay so welcome to xrstors(9) from the Kernel API Manual, bestie — this little icon is here to restore selected components from a kernel xstate buffer. Slay.

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✨ SYNOPSIS ✨

void xrstors (struct xregs_state *xstate , u64 mask );

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🎀 ARGUMENTS 🎀

• xstate — pointer to the buffer. It's literally the buffer, bestie.
• mask — feature mask to select the components to restore. It's the "which components are we bringing back?" picker.

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🧚 DESCRIPTION 🧚

The xstate buffer must be 64 byte aligned and correctly initialized — otherwise XRSTORS from that buffer can #GP. No cap, that's the warning, and it is not a cute look.

Proper usage is to restore the state which was saved with xsaves into xstate. Like, that's the intended pairing: xsaves tucks it away, xrstors brings it back. 💅

The feature mask must be a subset of the independent features. Periodt — that's the rule.

⚠️ reminder: 64 byte aligned + correctly initialized, or XRSTORS from that buffer can #GP. Keep it correct, keep it iconic. 🫶

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👀 SEE ALSO 👀

• kernel file ./arch/x86/kernel/fpu/xstate.c
• check_xtile_data_against_struct(9)
• __copy_xstate_to_uabi_buf(9)
• copy_xstate_to_uabi_buf(9)
• copy_uabi_to_xstate(9)
• xsaves(9)
• fpstate_realloc(9)
• fpu_xstate_prctl(9)

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🦋 cute lil sign-off: this page comes from ./arch/x86/kernel/fpu, dated October 2026, and it's the xrstors(9) page — mwah 💋