Oneplus phone update introduces hardware anti-rollback: Difference between revisions
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When the device powers on, the Primary Boot Loader (PBL) in the processor's ROM loads and verifies the eXtensible Boot Loader (XBL). The PBL reads the current anti-rollback version from the Qfprom fuses and compares it against the firmware's embedded version number. If the firmware version is lower than the fuse value, boot is rejected. When newer firmware successfully boots, the bootloader issues commands through Qualcomm's TrustZone to blow additional fuses, permanently recording the new minimum version.<ref name="xda-warning" /> | When the device powers on, the Primary Boot Loader (PBL) in the processor's ROM loads and verifies the eXtensible Boot Loader (XBL). The PBL reads the current anti-rollback version from the Qfprom fuses and compares it against the firmware's embedded version number. If the firmware version is lower than the fuse value, boot is rejected. When newer firmware successfully boots, the bootloader issues commands through Qualcomm's TrustZone to blow additional fuses, permanently recording the new minimum version.<ref name="xda-warning" /> | ||
EDL (Emergency Download Mode), historically the last-resort recovery option using USB interface 9008, cannot bypass this | EDL (Emergency Download Mode), historically the last-resort recovery option using USB interface 9008, cannot bypass this restriction. While EDL operates from the Primary Boot Loader ROM and allows direct storage writes, the eFuses remain in the processor silicon. EDL's Firehose programmers must be OEM-signed and contain their own anti-rollback versions; previously functional unbrick tools now fail because the fuse has been blown.<ref name="xda-warning" /> | ||
As explained on the XDA thread, the term "Fuse Blown" refers to the Qfprom eFuses (Electronic Fuses) inside the Snapdragon chipset being electrically switched from "0" to "1", effectively preventing older software from running, rather than a physical fuse burnout.<ref name="xda-warning" /> | As explained on the XDA thread, the term "Fuse Blown" refers to the Qfprom eFuses (Electronic Fuses) inside the Snapdragon chipset being electrically switched from "0" to "1", effectively preventing older software from running, rather than a physical fuse burnout.<ref name="xda-warning" /> | ||
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==Comparison with other manufacturers== | ==Comparison with other manufacturers== | ||
Anti-rollback | Anti-rollback mechanism exists across the smartphone industry, but implementations vary in their impact on users. | ||
[[Samsung Knox]] implements fuse-based security that trips permanently when non-OEM firmware is flashed, disabling Samsung Pay and Secure Folder. Android Authority noted that the new OnePlus implementation is functionally identical to Samsung's model, where eFuses serve as irreversible warrants of system integrity, punishing modification with permanent hardware states.<ref name="android-authority" /> | [[Samsung Knox]] implements fuse-based security that trips permanently when non-OEM firmware is flashed, disabling Samsung Pay and Secure Folder. Android Authority noted that the new OnePlus implementation is functionally identical to Samsung's model, where eFuses serve as irreversible warrants of system integrity, punishing modification with permanent hardware states.<ref name="android-authority" /> | ||