fw/services/process_management: allow unaligned relocation targets#1792
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The v4.24.0 loader hardening required every relocation target to be word aligned. Legacy SDK apps can have pointer slots at halfword offsets inside packed structs, e.g. 91 Dub v4.0 has seven such relocations per platform binary and was rejected on launch with "Invalid app relocation target[16]: 0x39da". A scan of the 400 most popular Rebble store apps found five affected (91 Dub v4.0, Timely, Rosewright A, Rosewright Chronograph, Directions); all of them worked before the hardening because Cortex-M supports unaligned LDR/STR. Drop the alignment requirement and access the slot bytewise via memcpy, mirroring the earlier fix for unaligned relocation table offsets. The bounds checks that actually prevent out of bounds writes in a privileged context are retained. Verified in QEMU (qemu_emery): 91 Dub v4.0 (basalt) and Rosewright A (emery) now load and render, and a current-SDK app still loads. Fixes FIRM-3562 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Signed-off-by: Joshua Jun <lets@throw.rocks>
gmarull
approved these changes
Jul 23, 2026
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The v4.24.0 loader hardening required every relocation target to be word aligned. Legacy SDK apps can have pointer slots at halfword offsets inside packed structs, e.g. 91 Dub v4.0 has seven such relocations per platform binary and was rejected on launch with "Invalid app relocation target[16]: 0x39da". A scan of the 400 most popular Rebble store apps found five affected (91 Dub v4.0, Timely, Rosewright A, Rosewright Chronograph, Directions); all of them worked before the hardening because Cortex-M supports unaligned LDR/STR.
Drop the alignment requirement and access the slot bytewise via memcpy, mirroring the earlier fix for unaligned relocation table offsets. The bounds checks that actually prevent out of bounds writes in a privileged context are retained. Verified in QEMU (qemu_emery): 91 Dub v4.0 (basalt) and Rosewright A (emery) now load and render, and a current-SDK app still loads.
Fixes FIRM-3562