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1 comment:

• File src/soc/mediatek/mt8192/spm.c:

  • Patch Set #35, Line 453:

    if (read32(&mtk_spm->md32pcm_dma0_src) != ptr ||
    	    read32(&mtk_spm->md32pcm_dma0_dst) != pmem_start ||
    	    read32(&mtk_spm->md32pcm_dma0_wppt) != pmem_words ||
    	    read32(&mtk_spm->md32pcm_dma0_wpto) != dmem_start ||
    	    read32(&mtk_spm->md32pcm_dma0_count) != total_words ||
    	    read32(&mtk_spm->md32pcm_dma0_con) != MD32PCM_DMA0_CON_VAL) {
    

    1. Slave mode won't be used in Chromebook. I save it for completing the mode selection. […]

    If compared to "checking consistency", I'd rather always kick IM to refetch our trusted data.

    Otherwise, I can imaging an exploit like

     -> boot into developer mode
     -> load a new malicious SPM firmware 
     -> reboot to normal (secure mode)
     -> firmware sees SPM regs already in good shape and didn't reload
     -> running malicious SPM in normal mode

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