scc/libs/mcode/include/x86/scc_x86_patch.h

#ifndef __SCC_X86_PATCH_H__
#define __SCC_X86_PATCH_H__
#include "scc_x86_encode.h"

// x86-64 重定位类型（由底层 patch 函数处理）
typedef enum {
    SCC_X86_PATCH_NONE,
    SCC_X86_PATCH_PC32,   // 32 位 PC 相对偏移（CALL/JMP/Jcc）
    SCC_X86_PATCH_ABS64,  // 64 位绝对地址（MOV reg, imm64）
    SCC_X86_PATCH_ABS32,  // 32 位绝对地址（MOV reg, imm32）
    SCC_X86_PATCH_DISP8,  // 8 位内存位移（[RIP+disp8] 或 [base+disp8]）
    SCC_X86_PATCH_DISP32, // 32 位内存位移（[RIP+disp32]）
} scc_x86_patch_type_t;

static inline void patch_bytes(scc_mcode_t *mcode, usize offset,
                               const void *data, usize size) {
    u8 *buf = (u8 *)scc_mcode_unsafe_data(mcode);
    usize total = scc_mcode_size(mcode);
    if (offset + size > total) {
        Panic("patch offset out of range: offset=%zu size=%zu total=%zu",
              offset, size, total);
    }
    scc_memcpy(buf + offset, data, size);
}

static inline int scc_x86_patch_disp(scc_mcode_t *mcode, usize offset,
                                     scc_x86_disp_t disp) {
    if (!mcode || disp.displacement_bits == 0)
        return -1;
    usize bytes = disp.displacement_bits / 8;
    if (bytes == 0) {
        bytes = 4; // RELBR 32
    }
    if (bytes != 1 && bytes != 2 && bytes != 4 && bytes != 8) {
        Panic("invalid displacement bits: %u", disp.displacement_bits);
    }
    // 将 displacement 截断到对应宽度（小端写入）
    i64 val = disp.displacement;
    switch (bytes) {
    case 1: {
        u8 v = (u8)val;
        patch_bytes(mcode, offset, &v, 1);
        break;
    }
    case 2: {
        u16 v = (u16)val;
        patch_bytes(mcode, offset, &v, 2);
        break;
    }
    case 4: {
        u32 v = (u32)val;
        patch_bytes(mcode, offset, &v, 4);
        break;
    }
    case 8:
        patch_bytes(mcode, offset, &val, 8);
        break;
    }
    return 0;
}

static inline int scc_x86_patch_brdisp(scc_mcode_t *mcode, usize offset,
                                       scc_x86_operand_value_t disp) {
    if (disp.kind != SCC_X86_OPR_RELBR && disp.kind != SCC_X86_OPR_RELOC) {
        Panic("patch_brdisp called with non-branch operand kind %d", disp.kind);
    }
    i32 brdisp;
    if (disp.kind == SCC_X86_OPR_RELBR)
        brdisp = disp.brdisp;
    else
        brdisp = (i32)disp.reloc.imm; // 从重定位占位中获取值（上层会先填好）
    patch_bytes(mcode, offset, &brdisp, 4);
    return 0;
}

static inline int scc_x86_patch_imm0(scc_mcode_t *mcode, usize offset,
                                     scc_x86_operand_value_t imm0) {
    // 注意：原声明未提供大小参数，我们假定调用者保证了正确的宽度。
    // 此处默认写入 8 字节（最常用）。若需要其他宽度，请使用扩展版本。
    if (imm0.kind != SCC_X86_OPR_IMM && imm0.kind != SCC_X86_OPR_RELOC) {
        Panic("patch_imm0 called with non-immediate operand kind %d",
              imm0.kind);
    }
    u64 val;
    if (imm0.kind == SCC_X86_OPR_IMM)
        val = imm0.imm0;
    else
        val = (u64)imm0.reloc.imm; // 从重定位占位中获取
    patch_bytes(mcode, offset, &val, 8);
    return 0;
}

/* ---------- 扩展：带大小的立即数 patch（推荐上层使用） ---------- */
static inline int scc_x86_patch_imm0_ex(scc_mcode_t *mcode, usize offset,
                                        u64 value, usize size) {
    if (size != 1 && size != 2 && size != 4 && size != 8)
        return -1;
    switch (size) {
    case 1: {
        u8 v = (u8)value;
        patch_bytes(mcode, offset, &v, 1);
        break;
    }
    case 2: {
        u16 v = (u16)value;
        patch_bytes(mcode, offset, &v, 2);
        break;
    }
    case 4: {
        u32 v = (u32)value;
        patch_bytes(mcode, offset, &v, 4);
        break;
    }
    case 8:
        patch_bytes(mcode, offset, &value, 8);
        break;
    }
    return 0;
}

static inline void scc_x86_patch(scc_mcode_t *mcode,
                                 scc_x86_patch_type_t patch_type, u64 offset,
                                 i64 value) {
    switch (patch_type) {
    case SCC_X86_PATCH_PC32:
        scc_x86_patch_brdisp(mcode, offset - 4,
                             scc_x86_op_relbr(value - offset));
        break;
    default:
        TODO();
        break;
    }
}

#endif /* __SCC_X86_PATCH_H__ */