From f3c8918b13a5226f53e7870d60436f812e5d9015 Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Sun, 28 Dec 2025 01:48:50 +0800
Subject: feat(user): add user-space build system and init process to test
 fork/wait

---
 src/kernel/initcode.S   |  8 ++++++++
 src/kernel/proc/proc.cc | 15 ++++++---------
 src/user/init.cc        | 34 ++++++++++++++++++++++++++++++++++
 src/user/user.ld        | 27 +++++++++++++++++++++++++++
 src/user/usys.S         | 31 +++++++++++++++++++++++++++++++
 5 files changed, 106 insertions(+), 9 deletions(-)
 create mode 100644 src/kernel/initcode.S
 create mode 100644 src/user/init.cc
 create mode 100644 src/user/user.ld
 create mode 100644 src/user/usys.S

(limited to 'src')

diff --git a/src/kernel/initcode.S b/src/kernel/initcode.S
new file mode 100644
index 0000000..8b56ce6
--- /dev/null
+++ b/src/kernel/initcode.S
@@ -0,0 +1,8 @@
+.section .rodata
+.global initcode_start
+.global initcode_end
+.align 4
+
+initcode_start:
+    .incbin "build/user/initcode"
+initcode_end:
diff --git a/src/kernel/proc/proc.cc b/src/kernel/proc/proc.cc
index 15a28b4..008f740 100644
--- a/src/kernel/proc/proc.cc
+++ b/src/kernel/proc/proc.cc
@@ -23,13 +23,8 @@ struct spinlock proc_lock;
 
 int nextpid = 1;
 
-
-uchar initcode[] = {
-    0x13, 0x05, 0x50, 0x05, // li a0, 85 ('U')
-    0x93, 0x08, 0x10, 0x00, // li a7, 1  (SYS_putc)
-    0x73, 0x00, 0x00, 0x00, // ecall
-    0x6f, 0xf0, 0x5f, 0xff  // j loop (-12)
-};
+extern char initcode_start[];
+extern char initcode_end[];
 
 struct Proc *myproc()
 {
@@ -277,7 +272,9 @@ namespace ProcManager
         }
 
         p->pagetable = VM::uvmcreate();
-        VM::uvminit(p->pagetable, initcode, sizeof(initcode));
+        
+        uint64 initcode_sz = initcode_end - initcode_start;
+        VM::uvminit(p->pagetable, (uchar *)initcode_start, initcode_sz);
         p->sz = PGSIZE;
 
         if (VM::mappages(p->pagetable, TRAPFRAME, PGSIZE,
@@ -402,6 +399,6 @@ namespace ProcManager
         }
     }
 
-    
+
 
 }
\ No newline at end of file
diff --git a/src/user/init.cc b/src/user/init.cc
new file mode 100644
index 0000000..3c42adf
--- /dev/null
+++ b/src/user/init.cc
@@ -0,0 +1,34 @@
+#include "user/user.h"
+
+int main();
+
+extern "C" void _start()
+{
+    exit(main());
+}
+
+int main()
+{
+    int pid = fork();
+
+    if (pid < 0)
+    {
+        write(1, "Fork failed\n", 12);
+        exit(1);
+    }
+
+    if (pid == 0)
+    {
+        write(1, "Hello from Child!\n", 18);
+        exit(0);
+    }
+    else
+    {
+        write(1, "Parent waiting...\n", 18);
+        wait(0);
+        write(1, "Parent: Child exited.\n", 22);
+    }
+
+    while (1);
+    return 0;
+}
\ No newline at end of file
diff --git a/src/user/user.ld b/src/user/user.ld
new file mode 100644
index 0000000..2111b14
--- /dev/null
+++ b/src/user/user.ld
@@ -0,0 +1,27 @@
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+SECTIONS
+{
+  . = 0x0;
+  
+  .text : {
+    *(.text.entry)
+    *(.text .text.*)
+  }
+
+  .rodata : {
+    . = ALIGN(16);
+    *(.rodata .rodata.*)
+  }
+
+  .data : {
+    . = ALIGN(16);
+    *(.data .data.*)
+  }
+
+  .bss : {
+    . = ALIGN(16);
+    *(.bss .bss.*)
+  }
+}
\ No newline at end of file
diff --git a/src/user/usys.S b/src/user/usys.S
new file mode 100644
index 0000000..e805d82
--- /dev/null
+++ b/src/user/usys.S
@@ -0,0 +1,31 @@
+#include "kernel/syscall.h"
+
+#define SYSCALL(name) \
+    .global name; \
+    name: \
+        li a7, SYS_ ## name; \
+        ecall; \
+        ret
+
+SYSCALL(fork)
+SYSCALL(exit)
+SYSCALL(wait)
+SYSCALL(pipe)
+SYSCALL(read)
+SYSCALL(write)
+SYSCALL(close)
+SYSCALL(kill)
+SYSCALL(exec)
+SYSCALL(open)
+SYSCALL(mknod)
+SYSCALL(unlink)
+SYSCALL(fstat)
+SYSCALL(link)
+SYSCALL(mkdir)
+SYSCALL(chdir)
+SYSCALL(dup)
+SYSCALL(getpid)
+SYSCALL(sbrk)
+SYSCALL(sleep)
+SYSCALL(uptime)
+SYSCALL(putc)
\ No newline at end of file
-- 
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