From ff3e779f22001dc98c12ce2a1a9e08142bfd244f Mon Sep 17 00:00:00 2001
From: Wesley Moore <wes@wezm.net>
Date: Sun, 9 Feb 2025 21:36:54 +1000
Subject: [PATCH] Fix segfault with the help of gdb via Nix
---
Makefile | 2 ++
calc.s | 4 ++++
cmain.c | 5 +++++
shell.nix | 12 ++++++++++++
4 files changed, 23 insertions(+)
create mode 100644 cmain.c
create mode 100644 shell.nix
diff --git a/Makefile b/Makefile
index 7517058..52cec4c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,7 @@
+CC=riscv64-unknown-elf-gcc
AS=riscv64-unknown-elf-as
ASFLAGS=-g -mabi=ilp32e -march=rv32ec
+CFLAGS=$(ASFLAGS)
LD=riscv64-unknown-elf-ld
all: calc.elf
diff --git a/calc.s b/calc.s
index e9cbcb4..f8c2dbd 100644
--- a/calc.s
+++ b/calc.s
@@ -108,7 +108,11 @@ regdump_loop:
la a0, buf # load address of buf into a0 as dest
li a2, 2 # copy 2 bytes
+ addi sp, sp, -4 # allocate stack space
+ sw ra, 0(sp) # save contents of ra
jal memcpy
+ lw ra, 0(sp) # save contents of ra
+ addi sp, sp, 4 # deallocate stack space
# append ': \n'
li t0, ':
sb t0, 0(a0)
diff --git a/cmain.c b/cmain.c
new file mode 100644
index 0000000..253e204
--- /dev/null
+++ b/cmain.c
@@ -0,0 +1,5 @@
+extern void regdump(void);
+
+void cmain(void) {
+ regdump();
+}
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 0000000..739359c
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,12 @@
+let
+ nixpkgs = fetchTarball "https://github.com/NixOS/nixpkgs/tarball/release-24.11";
+ pkgs = (import nixpkgs {}).pkgsCross.riscv32-embedded;
+in
+
+# callPackage is needed due to https://github.com/NixOS/nixpkgs/pull/126844
+pkgs.pkgsStatic.callPackage ({ mkShell, zlib, pkg-config, file, gdb }: mkShell {
+ # these tools run on the build platform, but are configured to target the host platform
+ nativeBuildInputs = [ pkg-config file gdb ];
+ # libraries needed for the host platform
+ buildInputs = [ zlib ];
+}) {}