insn_fetch_...ser_inatomic(9)

💅 insn_fetch_from_user_inatomic — Kernel API Manual energy 💅

okay so bestie, this page is insn_fetch_...ser_inatomic(9) from the Kernel API Manual, but the actual function we're swooning over is insn_fetch_from_user_inatomic. It's giving "copy instruction bytes from user-space memory while in atomic code" and honestly? iconic.

✨ NAME ✨

insn_fetch_from_user_inatomic — Copy instruction bytes from user-space memory while in atomic code.

🌸 SYNOPSIS 🌸

int insn_fetch_from_user_inatomic (struct pt_regs *regs , unsigned char
       buf[MAX_INSN_SIZE] );

🦋 ARGUMENTS 🦋

• regs — structure with register values as seen when entering kernel mode.
• buf — array to store the fetched instruction.

💖 DESCRIPTION 💖

Gets the linear address of the instruction and copies the instruction bytes to the buf. This function must be used in atomic context. No cap, that's the rule.

Then it's giving:

• number of instruction bytes copied.
• 0 if nothing was copied.
• -EINVAL if the linear address of the instruction could not be calculated.

🌈 SEE ALSO 🌈

Kernel file ./arch/x86/lib/insn-eval.c is the main character here, and it's linked up with:

• is_string_insn(9)
• insn_has_rep_prefix(9)
• get_seg_reg_override_idx(9)
• check_seg_overrides(9)
• resolve_default_seg(9)
• resolve_seg_reg(9)
• get_segment_selector(9)
• get_reg_offset_16(9)
• get_desc(9)
• insn_get_seg_base(9)
• get_seg_limit(9)
• insn_get_code_seg_params(9)
• insn_get_modrm_rm_off(9)
• insn_get_modrm_reg_off(9)
• insn_get_modrm_reg_ptr(9)
• get_seg_base_limit(9)
• get_eff_addr_reg(9)
• get_eff_addr_modrm(9)
• get_eff_addr_modrm_16(9)
• get_eff_addr_sib(9)
• get_addr_ref_16(9)
• get_addr_ref_32(9)
• get_addr_ref_64(9)
• insn_get_addr_ref(9)
• insn_fetch_from_user(9)
• insn_decode_from_regs(9)
• insn_decode_mmio(9)

Okay that's the whole page, bestie. This one's from ./arch/x86/lib, dated October 2026, and the footer label is insn_fetch_...ser_inatomic(9). Mwah 💋✨