Fix ARMv4T#177
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Some ARMv4T processors (like the ARM7TDMI) don't have a CP15. Therefore we must not set the SCTLR.TE bit on startup, because an MCR to that CP15 register will fail. This patch mixes the SCTLR.TE config with the FPU setup, and does the right thing according to pre-ARMv7 vs ARMv7, and whether there is an FPU or not. This was only caught by testing on a real ARM7TDMI - our ARMv4 testing thus far was done on QEMU emulating an ARM926. With this fix I can boot Rust code on an NXP LPC2138 microcontroller.
adamgreig
approved these changes
Jun 9, 2026
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Some ARMv4T processors (like the ARM7TDMI) don't have a CP15. Therefore we must not set the SCTLR.TE bit on startup, because an MCR to that CP15 register will fail.
This patch mixes the SCTLR.TE config with the FPU setup, and does the right thing according to pre-ARMv7 vs ARMv7, and whether there is an FPU or not.
This was only caught by testing on a real ARM7TDMI - our ARMv4 testing thus far was done on QEMU emulating an ARM926. With this fix I can boot Rust code on an NXP LPC2138 microcontroller.