firmware: use C versions of memcpy and memmove for ARM Cortex-M

commit 2f2b90535ae22c07ebaa19cc2f61cf9f0b0ee97f
Author: Aidan MacDonald <[email protected]>
Date:   Thu Jan 8 14:59:34 2026 +0000

    firmware: use C versions of memcpy and memmove for ARM Cortex-M
    
    The ARM assembly versions of memcpy and memmove try to
    directly modify the PC based on the number of bytes to
    be copied as an "optimization"; but this only works if
    instructions are guaranteed to be 4 bytes wide.
    
    This trick is completely broken on Cortex-M, since an
    instruction can be 2-4 bytes wide: for example a memcpy
    of 4 bytes ends up storing 32 bytes worth of garbage to
    the target address!
    
    Use the C memcpy/memmove implementations for Cortex-M
    instead; fixing the ASM version is more trouble than
    it's worth.
    
    Change-Id: I695587fd585ec25ef276f2dbc61e2290b7015e13

diff --git a/firmware/asm/SOURCES b/firmware/asm/SOURCES
index 5aa9b1c0f7..dc8d7b5dfc 100644
--- a/firmware/asm/SOURCES
+++ b/firmware/asm/SOURCES
@@ -1,5 +1,7 @@
 #if defined(CPU_ARM)
+#if defined(CPU_ARM_CLASSIC)
 arm/ffs.S
+#endif
 arm/memset16.S
 #elif defined(CPU_MIPS)
 mips/ffs.S
@@ -13,11 +15,17 @@ memset16.c
 #endif
 
 #if (CONFIG_PLATFORM & PLATFORM_NATIVE) || defined(HAVE_ROCKBOX_C_LIBRARY)
-#if defined(CPU_ARM)
+#if defined(CPU_ARM_CLASSIC)
 arm/memcpy.S
 arm/memmove.S
 arm/memset.S
 strlen.c
+#elif defined(CPU_ARM_MICRO)
+memcpy.c
+mempcpy.c
+memmove.c
+arm/memset.S
+strlen.c
 #elif defined(CPU_MIPS)
 mips/memcpy.S
 memmove.c
-- 
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