From 4cacdeb01233a82d47b54c94b1dda10ec48e63e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20R=C3=B6ger?= <jonas.roeger@tu-dortmund.de>
Date: Mon, 20 Apr 2026 23:50:04 +0200
Subject: [PATCH] feat(sys): add sys lib

---
 CMakeLists.txt                   | 15 ++++++++++++---
 app/nolibc.c                     | 14 +-------------
 include/c-libs/sys/syscall.h     | 21 +++++++++++++++++++++
 src/sys/entry.s                  | 20 ++++++++++++++++++++
 src/sys/syscall.c                |  2 ++
 app/entry.s => src/sys/syscall.s | 18 +-----------------
 6 files changed, 57 insertions(+), 33 deletions(-)
 create mode 100644 include/c-libs/sys/syscall.h
 create mode 100644 src/sys/entry.s
 create mode 100644 src/sys/syscall.c
 rename app/entry.s => src/sys/syscall.s (70%)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f827595..01afdc6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,8 +17,17 @@ target_link_libraries(strings PRIVATE c-libs)
 add_executable(rc ${CMAKE_CURRENT_SOURCE_DIR}/app/rc.c)
 target_link_libraries(rc PRIVATE c-libs)
 
-add_executable(nolibc ${CMAKE_CURRENT_SOURCE_DIR}/app/nolibc.c
-                      ${CMAKE_CURRENT_SOURCE_DIR}/app/entry.s)
+add_library(
+  sys STATIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/entry.s
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/syscall.s
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/syscall.c)
+target_include_directories(
+  sys PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+             $<INSTALL_INTERFACE:include>)
+
+add_executable(nolibc ${CMAKE_CURRENT_SOURCE_DIR}/app/nolibc.c)
+target_link_libraries(nolibc PRIVATE sys)
 target_compile_options(
   nolibc PRIVATE -fno-asynchronous-unwind-tables -fno-unwind-tables
                  -fno-stack-protector -ffunction-sections -fdata-sections)
@@ -50,7 +59,7 @@ include(CMakePackageConfigHelpers)
 include(GNUInstallDirs)
 
 install(
-  TARGETS c-libs
+  TARGETS c-libs sys
   EXPORT c-libs
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
diff --git a/app/nolibc.c b/app/nolibc.c
index 3636b91..5085c71 100644
--- a/app/nolibc.c
+++ b/app/nolibc.c
@@ -1,16 +1,4 @@
-void *syscall5(void *number, void *arg1, void *arg2, void *arg3, void *arg4,
-               void *arg5);
-
-typedef unsigned long int size_t;
-typedef long int ssize_t;
-
-static ssize_t write(int fd, void const *data, size_t nbytes) {
-  return (ssize_t)syscall5((void *)1, /* SYS_write, call number 1 */
-                           (void *)(size_t)fd, (void *)data, (void *)nbytes,
-                           0, /* Ignored */
-                           0  /* Ignored */
-  );
-}
+#include <c-libs/sys/syscall.h>
 
 int main() {
   write(0, "Hello World!\n", 13);
diff --git a/include/c-libs/sys/syscall.h b/include/c-libs/sys/syscall.h
new file mode 100644
index 0000000..d1e02bf
--- /dev/null
+++ b/include/c-libs/sys/syscall.h
@@ -0,0 +1,21 @@
+#ifndef CLIBS_SYS_SYSCALL_H
+#define CLIBS_SYS_SYSCALL_H
+
+#include <asm/types.h>
+#include <asm/unistd.h>
+
+void *syscall5(void *number, void *arg1, void *arg2, void *arg3, void *arg4,
+               void *arg5);
+
+__s64 write(int fd, void const *data, __u64 nbytes);
+
+#endif
+
+#ifdef CLIBS_SYS_SYSCALL_IMPL
+
+__s64 write(int fd, void const *data, __u64 nbytes) {
+  return (__s64)syscall5((void *)__NR_write, (void *)(__u64)fd, (void *)data,
+                         (void *)nbytes, 0, 0);
+}
+
+#endif
diff --git a/src/sys/entry.s b/src/sys/entry.s
new file mode 100644
index 0000000..c0c7a4e
--- /dev/null
+++ b/src/sys/entry.s
@@ -0,0 +1,20 @@
+.global _start
+
+
+_start: 
+    /* Load argc -> rdi, argv[0] -> rsi */
+    xor %rbp, %rbp
+    pop %rdi
+    mov %rsp, %rsi
+
+    /* align stack pointer to 16-bits */
+    and $0xFFFFFFFFFFFFFFF0, %rsp
+    
+    call main
+
+    /* Exit with ret val of main */
+    mov %rax, %rdi
+    mov $0x3C, %rax
+    syscall
+
+.section .note.GNU-stack,"",@progbits
diff --git a/src/sys/syscall.c b/src/sys/syscall.c
new file mode 100644
index 0000000..a469f5b
--- /dev/null
+++ b/src/sys/syscall.c
@@ -0,0 +1,2 @@
+#define CLIBS_SYS_SYSCALL_IMPL
+#include <c-libs/sys/syscall.h>
diff --git a/app/entry.s b/src/sys/syscall.s
similarity index 70%
rename from app/entry.s
rename to src/sys/syscall.s
index ed1e48a..48da149 100644
--- a/app/entry.s
+++ b/src/sys/syscall.s
@@ -1,20 +1,4 @@
-.global _start, syscall5
-
-
-_start: 
-    /* Load argc -> rdi, argv[0] -> rsi */
-    xor %rbp, %rbp
-    pop %rdi
-    mov %rsp, %rsi
-
-    and $0xFFFFFFFFFFFFFFF0, %rsp
-    
-    call main
-
-    /* Exit with ret val of main */
-    mov %rax, %rdi
-    mov $0x3C, %rax
-    syscall
+.global syscall5
 
 syscall5:
     mov    %rdi, %rax /* %rax (syscall number)  = func param 1 (%rdi)    */