Hi, I have written (copied from here https://github.com/bztsrc/raspi3-tutorial/tree/master/0F_executionlevel) a small bare metal program to switch exception level from EL2 to EL1 in Raspberry Pi 3B. The program is linked to load at the address 0x80000. The stripped version of the ELF is directly loaded through the "config.txt" file (without U-Boot) and it works. It is able to access the mini UART and print a message from EL1.
Now I have modified the same program to load at the address (0x1000000) by modifying the linker (link.ld) file. Stripped it using objcopy. started the board with U-Boot. From U-boot prompt loaded the binary to the address 0x1000000 (using tftpboot). Then initiated the execution using go 0x1000000.
This ends up in a board reset with the following error.
U-Boot> go 0x1000000 ## Starting application at 0x01000000 ... "Synchronous Abort" handler, esr 0x86000004, far 0x13af5d330 elr: 00000000ffc92330 lr : 00000000ffc92330 (reloc) elr: 000000013af5d330 lr : 000000013af5d330 x0 : 0000000003000022 x1 : 0000000000000001 x2 : 0000000001000084 x3 : 0000000001000000 x4 : 0000000000000000 x5 : 0000000000001680 x6 : 0000000000000010 x7 : 0000000000000008 x8 : 0000000000000001 x9 : 0000000000000010 x10: 0000000000000004 x11: 000000003e96cea0 x12: 0000000000000001 x13: 000000003e96cea0 x14: 0000000000000000 x15: 0000000000000004 x16: 0000000000000000 x17: 0000000000000000 x18: 000000003af46d60 x19: 000000003af3e9c0 x20: 000000003b365f20 x21: 000000003af3eaa0 x22: 0000000000000000 x23: 000000000000000a x24: 0000000000000000 x25: 000000003af5d310 x26: 0000000000000000 x27: 0000000000000000 x28: 000000003af5d400 x29: 0000000000000060
Code: "Synchronous Abort" handler, esr 0x96000004, far 0x13af5d320 elr: 0000000000082b10 lr : 0000000000082af0 (reloc) elr: 000000003b34db10 lr : 000000003b34daf0 x0 : 000000003b3c05c5 x1 : 000000003ebe9a00 x2 : 0000000000000040 x3 : 000000000000003f x4 : 0000000000000000 x5 : 0000000000001680 x6 : 0000000000000010 x7 : 0000000000000008 x8 : 0000000000000001 x9 : 0000000000000010 x10: 0000000000000004 x11: 000000003eb2ea40 x12: 0000000000000001 x13: 000000003eb2ea40 x14: 0000000000000000 x15: 0000000000000004 x16: 0000000000000000 x17: 0000000000000000 x18: 000000003af46d60 x19: 000000013af5d320 x20: 000000003b3c5000 x21: 00000000fffffffc x22: 000000003b3c6dd5 x23: 000000003b3c05c5 x24: 0000000000000000 x25: 000000003af5d310 x26: 0000000000000000 x27: 0000000000000000 x28: 000000003af5d400 x29: 000000003af3e7f0
Code: d1004273 913756d6 aa0003f7 12800075 (b9400261) Resetting CPU ...
I built U-Boot with default configuration for raspberry-pi3 and arm64. My program crashed on both of them. This error log is from BCM2835-arm64 U-Boot build.
Is there any specific requirement for U-Boot which should be met by the bare metal program? I have been struggling with this for quite some time. Any help/hint is (to some documentation at lleast) greatly appreciated.
Thanks a lot, Little