HiFive RevB startup.s location?

Cosmic · January 31, 2020, 11:07am

Hello,

I’m a new user to the HiFive board and I’m part of a team of students working on a project to port a racing drone OS called CleanFlight to the HiFive Revb board (for a proof of concept for Risk-V things). I’ve been using Freedom Studio to mess around with the board a bit and haven’t been able to locate the assembly language file or something similar to a Startup.s which should handle bringing the board up at power on and direct it to look to a specific place in memory for a user loaded program, setup the stack, the interrupt handler and other things.

Does anyone know where such a file is located, or if for some reason there is no equivalent on this board have an explanation as to why?

Thank you!

nick.knight · January 31, 2020, 7:54pm

Hi Cosmic,

Assuming you’re using the Freedom Metal library, the following two files have some relevant details:

github.com

sifive/freedom-metal/blob/v201908-branch/src/entry.S

/* Copyright 2018 SiFive, Inc */
/* SPDX-License-Identifier: Apache-2.0 */

/* This code executes before _start, which is contained inside the C library.
 * In embedded systems we want to ensure that _enter, which contains the first
 * code to be executed, can be loaded at a specific address.  To enable this
 * feature we provide the '.text.metal.init.enter' section, which is
 * defined to have the first address being where execution should start. */
.section .text.metal.init.enter
.global _enter
_enter:
    .cfi_startproc

    /* Inform the debugger that there is nowhere to backtrace past _enter. */
    .cfi_undefined ra

    /* The absolute first thing that must happen is configuring the global
     * pointer register, which must be done with relaxation disabled because
     * it's not valid to obtain the address of any symbol without GP
     * configured.  The C environment might go ahead and do this again, but

This file has been truncated. show original

github.com

sifive/freedom-metal/blob/v201908-branch/gloss/crt0.S

/* Copyright (c) 2017-2018  SiFive Inc. All rights reserved.

   This copyrighted material is made available to anyone wishing to use,
   modify, copy, or redistribute it subject to the terms and conditions
   of the FreeBSD License.   This program is distributed in the hope that
   it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
   including the implied warranties of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  A copy of this license is available at
   http://www.opensource.org/licenses.
*/

/* crt0.S: Entry point for RISC-V METAL programs. */

.section .text.libgloss.start
.global _start
.type   _start, @function

  /* _start is defined by the METAL to have been called with the following
   * arguments:
   *   a0: the hart ID of the currently executing hart.  Harts can start at

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Feel free to ask follow-up questions. Thanks for trying out the Freedom platform!

Best,
Nick Knight

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HiFive RevB startup.s location?

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