calculate end-of-stack value from chip configs (#12)

build.zig

@@ -16,7 +16,7 @@ pub fn build(b: *std.build.Builder) !void {
 
     const BuildConfig = struct { name: []const u8, backing: Backing, supports_uart: bool = true };
     const all_backings = [_]BuildConfig{
-        //BuildConfig{ .name = "boards.arduino_nano", .backing = Backing{ .board = pkgs.boards.arduino_nano } },
+        //BuildConfig{ .name = "boards.arduino_nano", .backing = Backing{ .board = boards.arduino_nano } },
         BuildConfig{ .name = "boards.mbed_lpc1768", .backing = Backing{ .board = boards.mbed_lpc1768 } },
         //BuildConfig{ .name = "chips.atmega328p", .backing = Backing{ .chip = pkgs.chips.atmega328p } },
         BuildConfig{ .name = "chips.lpc1768", .backing = Backing{ .chip = chips.lpc1768 } },

src/main.zig

@@ -63,6 +63,18 @@ pub fn addEmbeddedExecutable(
     };
 
     {
+        // TODO: let the user override which ram section to use the stack on,
+        // for now just using the first ram section in the memory region list
+        const first_ram = blk: {
+            for (chip.memory_regions) |region| {
+                if (region.kind == .ram)
+                    break :blk region;
+            } else {
+                std.log.err("no ram memory region found for setting the end-of-stack address", .{});
+                return error.NoRam;
+            }
+        };
+
         std.fs.cwd().makeDir(std.fs.path.dirname(config_file_name).?) catch {};
         var config_file = try std.fs.cwd().createFile(config_file_name, .{});
         defer config_file.close();
@@ -74,6 +86,7 @@ pub fn addEmbeddedExecutable(
 
         try writer.print("pub const chip_name = .@\"{}\";\n", .{std.fmt.fmtSliceEscapeUpper(chip.name)});
         try writer.print("pub const cpu_name = .@\"{}\";\n", .{std.fmt.fmtSliceEscapeUpper(chip.cpu.name)});
+        try writer.print("pub const end_of_stack = 0x{X:0>8};\n\n", .{first_ram.offset + first_ram.length});
     }
 
     const microzig_pkg = Pkg{
@@ -81,6 +94,11 @@ pub fn addEmbeddedExecutable(
         .path = .{ .path = root_path ++ "core/microzig.zig" },
     };
 
+    const config_pkg = Pkg{
+        .name = "microzig-config",
+        .path = .{ .path = config_file_name },
+    };
+
     const chip_pkg = Pkg{
         .name = "chip",
         .path = .{ .path = chip.path },
@@ -90,16 +108,11 @@ pub fn addEmbeddedExecutable(
             Pkg{
                 .name = "cpu",
                 .path = .{ .path = chip.cpu.path },
-                .dependencies = &[_]Pkg{ microzig_pkg, pkgs.mmio },
+                .dependencies = &[_]Pkg{ microzig_pkg, pkgs.mmio, config_pkg },
             },
         },
     };
 
-    const config_pkg = Pkg{
-        .name = "microzig-config",
-        .path = .{ .path = config_file_name },
-    };
-
     const exe = builder.addExecutable(name, root_path ++ "core/start.zig");
 
     // might not be true for all machines (Pi Pico), but

src/modules/cpus/cortex-m3/cortex-m3.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const config = @import("microzig-config");
 
 pub fn sei() void {
     asm volatile ("cpsie i");
@@ -56,8 +57,7 @@ pub const startup_logic = struct {
     };
 
     export const vectors linksection("microzig_flash_start") = VectorTable{
-        // TODO: How to compute/get the initial stack pointer?
-        .initial_stack_pointer = 0x1000_7FFC, // HACK: hardcoded, do not keep!
+        .initial_stack_pointer = config.end_of_stack,
         .reset = _start,
     };
 

src/modules/cpus/cortex-m4/cortex-m4.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const config = @import("microzig-config");
 
 pub fn sei() void {
     asm volatile ("cpsie i");
@@ -56,8 +57,7 @@ pub const startup_logic = struct {
     };
 
     export const vectors linksection("microzig_flash_start") = VectorTable{
-        // TODO: How to compute/get the initial stack pointer?
-        .initial_stack_pointer = 0x2000_A000, // HACK: hardcoded, do not keep!
+        .initial_stack_pointer = config.end_of_stack,
         .reset = _start,
     };