How do i set up instruction & data memory address when using "riscv32-unknown-elf-gcc"?

Question

I designed RISCV32IM processor, and I used "riscv32-unknown-elf-gcc" to generate code for testing.

However, the PC(instruction memory address) value and data memory address of the generated code had arbitrary values. I used this command:

riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c

Can I know if I can set the instruction and data memory address I want?

Thanks.

Thank you for answer.

I designed only HW, and this is my first time using the SW tool chain. Even if my question is rudimentary, please understand.

The figure is the result of the "-v" option. enter image description here

I can't modify the script file because I use riscv tool chain in DOCKER environment. So, I tried to copy the script file (elf32lriscv.x), modify it. I modified it to 0x10000 ==> 0x00000. The file name of the copied script is "test5.x".

And it was executed as follows. What am I doing wrong?

enter image description here

Answer 1

The riscv compiler is using the default linker script to place text and date section... .

If you add -v option to your command line riscv32-unknown-elf-gcc -v -march=rv32im -mabi=ilp32 -nostartfiles test.c, you will see the linker script used by collect 2 ( normally it will be -melf32lriscv . you can find the linker script in ${path_to_toolchain}/riscv32-unknown-elf/lib/ldscripts/ (the default one is .x).

You can also use riscv32-unknown-elf-ld --verbose like explained by @Frant. However , you need to be careful if the toolchain was compiled with enable multilib and you compile for rv64 but the default is rv32 or vice versa. It is not the case probably, but to be sure you can specify the arch with -A elf32riscv for an rv32.

To Set the addresses you can create your own linker script or copy and modify the default one. You can only modify the executable start like explained by @Frant or make more modification and place whatever you want where you want.

Once your own linker script ready you can pass it to the linker with -Wl,-T,${own_linker_script }. you command will be riscv32-unknown-elf-gcc -march=rv32im -mabi=ilp32 -nostartfiles test.c -Wl,-T,${own_linker_script }