riscv-python/start_newlib.S at main · ccattuto/riscv-python · GitHub

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    .section .init
    .globl _start

_start:
    .option push
    .option norelax
    la sp, __stack_top          # initialize the stack pointer
    la gp, __global_pointer$    # initialize the global pointer
    .option pop

    # save a0 and a1: they are used to pass arguments to main()
    mv s0, a0
    mv s1, a1

    # initialize .bss
    la   t0, __bss_start
    la   t1, __bss_end
z_bss:
    sw   zero, 0(t0)
    addi t0, t0, 4
    blt  t0, t1, z_bss

    # initialize .sbss
    la   t0, __sbss_start
    la   t1, __sbss_end
z_sbss:
    sw   zero, 0(t0)
    addi t0, t0, 4
    blt  t0, t1, z_sbss

    # initialize Newlib
    call __libc_init_array

    # restore a0 and a1
    mv a0, s0
    mv a1, s1

    call main

halt:
    mv a0, a0           # main's return value already in a0
    li a7, 93           # syscall ID for exit (newlib/Linux-style)
    ecall
# unreachable
1:
    j 1b