insn_get_modrm_reg_off(9)

insn_get_modrm_reg_off(9) 💅

okay so bestie, welcome to this Kernel API Manual page — it’s literally all about insn_get_modrm_reg_off, and it’s shorter than ur attention span on a good day. let’s get into it ✨

🌸 NAME 🌸

insn_get_modrm_reg_off — obtain the register in the reg part of the ModRM byte. periodt 💖

🎀 SYNOPSIS 🎀

int insn_get_modrm_reg_off (struct insn *insn , struct pt_regs *regs );

that signature? iconic. no cap.

🦋 ARGUMENTS 🦋

• insn — the instruction containing the ModRM byte. yes bestie, that one.
• regs — the register values as seen when entering kernel mode. exactly like the manual says, don’t @ me.

🌈 DESCRIPTION 🌈

so the function gets you the register indicated by the reg part of the ModRM byte. that register is obtained as an offset from the base of pt_regs. that’s the vibe check: reg part in, offset out, slay 💅

👑 SEE ALSO 👑

kernel file ./arch/x86/lib/insn-eval.c is where the friend group lives — here’s the whole crew, fr fr:

• 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_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_fetch_from_user_inatomic(9)
• insn_decode_from_regs(9)
• insn_decode_mmio(9)

mwah 💋 — this has been your Kernel API Manual moment, source/version ./arch/x86/lib, dated October 2026. catch u in the kernel, bestie 🫶✨