doc/topics/sdk/boot/uboot-code-relocate.html

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                        <div class=" wh_topic_content body "><main role="main"><article class="- topic/topic concept/concept topic concept" role="article" aria-labelledby="ariaid-title1"><span class="edit-link" style="font-size:12px; opacity:0.6; text-align:right; vertical-align:middle"><a target="_blank" href="http://172.16.35.88/tasks/jdssno1uvvbf2mltu9kb9v3if05d5gopuakboe8hlud18rma/edit/F:/aicdita/aicdita-cn/topics/sdk/boot/uboot-code-relocate.dita">Edit online</a></span><h1 class="- topic/title title topictitle1" id="ariaid-title1">代码重定位</h1><div class="date inPage">4 Dec 2024</div><div style="color: gray;">
                    Read time: 1 minute(s)
                </div><div class="- topic/body concept/conbody body conbody"><div class="- topic/p p" data-ofbid="d276142e22__20250121171748">通常内核的代码段放在 DRAM 的开始位置，U-Boot 的代码位置放到 DRAM 的末端。 但是由于不同项目所用的 DRAM 大小不一致，为了方便，将 U-Boot
            的链接地址也定义在 DRAM 比较前面的固定位置。在加载 U-Boot 初始化完 DRAM 之后，U-Boot 读取当前平台的 DRAM 大小， 然后在加载 Kernel
            之前将自身代码段和数据段等信息重定位到 DRAM 的末端继续运行， 将 DRAM 的前端空间让给
            Kernel。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_e2z_gl3_pzb__codeblock_pdf_jmr_c1c" data-ofbid="concept_e2z_gl3_pzb__codeblock_pdf_jmr_c1c">_start <em class="hl-comment">// arch/riscv/cpu/start.S</em>
|-&gt; save_boot_params <em class="hl-comment">// arch/riscv/mach-artinchip/lowlevel_init.S</em>
|-&gt; ...
|-&gt; board_init_f(); <em class="hl-comment">// common/board_f.c</em>
    |-&gt; setup_reloc(); <em class="hl-comment">// common/board_f.c</em>
    |-&gt; jump_to_copy(); <em class="hl-comment">// common/board_f.c</em>
        |-&gt; relocate_code(); <em class="hl-comment">// arch/riscv/cpu/start.S</em>
            |       <em class="hl-comment">// RISCV 上的实现，relocate 之后，函数不返回，直接跳转到 board_init_r 执行</em>
            |-&gt; invalidate_icache_all()
            |-&gt; flush_dcache_all()
            |-&gt; board_init_r();</pre></div><div class="- topic/p p" data-ofbid="d276142e26__20250121171748">重定位的具体位置 <code class="+ topic/ph pr-d/codeph ph codeph">gd-&gt;relocaddr</code> 的计算可查看 <span class="+ topic/ph sw-d/filepath ph filepath">common/board_f.c</span>
            ：<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_e2z_gl3_pzb__codeblock_khx_jmr_c1c" data-ofbid="concept_e2z_gl3_pzb__codeblock_khx_jmr_c1c"><strong class="hl-keyword">static</strong> <strong class="hl-keyword">const</strong> init_fnc_t init_sequence_f[] = {
    ...
    setup_dest_addr,
    reserve_round_<span class="hl-number">4</span>k,
    reserve_mmu,
    reserve_video,
    reserve_trace,
    reserve_uboot,
    ...
    setup_reloc,
    NULL,
};</pre></div><p class="- topic/p p" data-ofbid="d276142e36__20250121171748">最终 <code class="+ topic/ph pr-d/codeph ph codeph">gd-&gt;reloc_off</code> 的计算，在 <span class="+ topic/ph sw-d/filepath ph filepath">setup_reloc</span> 中完成。</p><div class="- topic/note note note note_note" id="concept_e2z_gl3_pzb__note_nzy_tbh_bzb" data-ofbid="concept_e2z_gl3_pzb__note_nzy_tbh_bzb"><span class="note__title">注：</span> 
            <p class="- topic/p p" data-ofbid="d276142e46__20250121171748">如果 CONFIG_SYS_TEXT_BASE == relocation address，则不需要做重定位的工作， 可以节省启动时间。这个需要根据当前项目的 DRAM
                大小进行计算 CONFIG_SYS_TEXT_BASE 的值。</p>
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