From 25bec21f20208a9369656a337cf5325e7b3a5a8d Mon Sep 17 00:00:00 2001
From: taitep <taitep@taitep.se>
Date: Sun, 4 Jan 2026 18:51:23 +0100
Subject: Initial commit

---
 src/crt0.S | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 src/crt0.S

(limited to 'src/crt0.S')

diff --git a/src/crt0.S b/src/crt0.S
new file mode 100644
index 0000000..97228c1
--- /dev/null
+++ b/src/crt0.S
@@ -0,0 +1,70 @@
+# vim: filetype=asm:
+/* Copyright (c) 2017  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.
+
+   Modified in 2026 by taitep to run bare metal on the TRVE emulator,
+*/
+
+#include "newlib.h"
+
+#=========================================================================
+# crt0.S : Entry point for RISC-V user programs
+#=========================================================================
+
+  .text
+  .global _start, _exit, _heap_end
+  .type   _start, @function
+_start:
+  # Initialize the stack pointer
+  la sp, _stack_top
+
+  # Initialize global pointer
+.option push
+.option norelax
+1:auipc gp, %pcrel_hi(__global_pointer$)
+  addi  gp, gp, %pcrel_lo(1b)
+.option pop
+
+  # Clear the bss segment
+  la      a0, _bss_start
+  la      a2, _bss_end
+  sub     a2, a2, a0
+  li      a1, 0
+  call    memset
+
+  # Clear the sbss segment
+  la      a0, _sbss_start
+  la      a2, _sbss_end
+  sub     a2, a2, a0
+  li      a1, 0
+  call    memset
+
+#ifdef _LITE_EXIT
+  # Make reference to atexit weak to avoid unconditionally pulling in
+  # support code.  Refer to comments in __atexit.c for more details.
+  .weak   atexit
+  la      a0, atexit
+  beqz    a0, .Lweak_atexit
+  .weak   __libc_fini_array
+#endif
+
+  la      a0, __libc_fini_array   # Register global termination functions
+  call    atexit                  #  to be called upon exit
+#ifdef _LITE_EXIT
+.Lweak_atexit:
+#endif
+  call    __libc_init_array       # Run global initialization functions
+
+  call    main
+  call    exit
+_exit: j _exit
+  .size  _start, .-_start
+_heap_end:
+  .dword _heap_start
-- 
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