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On Mediatek devices, the same preloader.bin is in mmcblk0boot0 and mmcblk0boot1, why does it need to be in both partitions?

Dinesh Gami
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  • This is not always the case: https://android.stackexchange.com/a/218346/218526. But if the second boot area partition had no use, OEM might have used it for bootloader backup. Did you hash both partitions and they are 100% identical? – Irfan Latif Sep 10 '20 at 18:15
  • On the link you mentioned, where does it explain by why the preloader needs to be in both partitions? Yes the preloader.bin found in both partitions are identical. – Dinesh Gami Sep 10 '20 at 18:40
  • The link explains that both partitions are not identical. Search the role of idme print command on MTK devices. – Irfan Latif Sep 10 '20 at 18:51
  • Btw bootloader partitions have a backup copy usually e.g. aboot and sbl on Qualcomm devices. This is to make sure if updating bootloader fails for some reason (or the partition geta corrupted for some other reason, though not very likely), device shouldn't be bricked. So a duplicate bootloader partition isn't strange, and nothing to worry about. – Irfan Latif Sep 11 '20 at 19:00

1 Answers1

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Both the preloader BIN files in the mmcblk0boot0 and mmcblk0boot1 partitions are identical. The reason for this is in case the mmcblk0boot0 becomes corrupt, the device is still able to boot up.

Andrew T.
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Jitesh Kumar
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  • You missed my statement: "OEM might have used it for bootloader backup". So I already agreed with what you are saying. But I'm dead sure that not all MTK devices have preloader (or bootloader) on both boot area partitions. I have physically analyzed more than one devices where raw mmcblk0boot1 partition contained device specific information like MAC address, serial number etc. idme print dumps that information to human readable form. – Irfan Latif Sep 11 '20 at 16:42
  • When you were analyzing the mmcblk0boot1 partition , did you use sp flash tool to make a dump of that partition? – Jitesh Kumar Sep 11 '20 at 18:07
  • Why would one need a special tool just to create partition dump? Why not simply dd? // Btw I checked hash of both partitions, ran strings on both, watched strace idme print running which paths it read, studied somewhat how /proc/idme/ works. So I have no doubt at all in what I'm saying. – Irfan Latif Sep 11 '20 at 18:13
  • Very unlikely (0.000001% chance) the preloader files between mmcblk0boot0 and mmcblk0boot1 are not identical. Which mediatek device did you test on? – Jitesh Kumar Sep 11 '20 at 18:26
  • May I ask why 0.000001%? Is this a standard? // The one I tested when writing the answer linked in first comment was Amazon KFFOWI (Ford) tablet. – Irfan Latif Sep 11 '20 at 18:38