feat(sys): add malloc

CMakeLists.txt

@@ -21,7 +21,8 @@ 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)
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/syscall.c
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/memory.c)
 target_include_directories(
   sys PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
              $<INSTALL_INTERFACE:include>)
@@ -29,8 +30,9 @@ target_include_directories(
 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)
+  nolibc
+  PRIVATE -fno-asynchronous-unwind-tables -fno-unwind-tables
+          -fno-stack-protector -ffunction-sections -fdata-sections -fno-builtin)
 target_link_options(
   nolibc
   PRIVATE

app/nolibc.c

@@ -1,6 +1,19 @@
+#include <c-libs/sys/memory.h>
 #include <c-libs/sys/syscall.h>
 
+void strcpy(char *dst, const char *src) {
+  int ix = 0;
+  do {
+    dst[ix] = src[ix];
+  } while (src[ix++]);
+}
+
 int main() {
-  write(0, "Hello World!\n", 13);
+  char *str = malloc(14);
+  strcpy(str, "Hello World!\n");
+
+  write(0, str, 13);
+
+  munmap(str, 14);
   return 0;
 }

include/c-libs/sys/memory.h

@@ -0,0 +1,17 @@
+#ifndef CLIBS_SYS_MEMORY_H
+#define CLIBS_SYS_MEMORY_H
+
+#include <c-libs/sys/syscall.h>
+#include <linux/mman.h>
+
+void *malloc(__u64 size);
+
+#endif
+
+#ifdef CLIBS_SYS_MEMORY_IMPL
+
+void *malloc(__u64 size) {
+  return mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1,
+              0);
+}
+#endif

include/c-libs/sys/syscall.h

@@ -1,14 +1,22 @@
 #ifndef CLIBS_SYS_SYSCALL_H
 #define CLIBS_SYS_SYSCALL_H
 
-#include <asm/types.h>
-#include <asm/unistd.h>
+#include <linux/types.h>
+#include <linux/unistd.h>
 
 void *syscall5(void *number, void *arg1, void *arg2, void *arg3, void *arg4,
                void *arg5);
 
+void *syscall6(void *number, void *arg1, void *arg2, void *arg3, void *arg4,
+               void *arg5, void *arg6);
+
 __s64 write(int fd, void const *data, __u64 nbytes);
 
+void *mmap(void *addr, __u64 len, __u64 prot, __u64 flags, __u64 fd,
+           __s64 offset);
+
+int munmap(void *addr, __u64 len);
+
 #endif
 
 #ifdef CLIBS_SYS_SYSCALL_IMPL
@@ -18,4 +26,17 @@ __s64 write(int fd, void const *data, __u64 nbytes) {
                          (void *)nbytes, 0, 0);
 }
 
+void *mmap(void *addr, __u64 len, __u64 prot, __u64 flags, __u64 fd,
+           __s64 offset) {
+  return syscall6((void *)__NR_mmap, (void *)addr, (void *)len, (void *)prot,
+                  (void *)flags, (void *)fd, (void *)offset);
+}
+
+int munmap(void *addr, __u64 len) {
+  long val = (long)syscall5((void *)__NR_munmap, addr, (void *)len, (void *)0,
+                            (void *)0, (void *)0);
+
+  return (int)val;
+}
+
 #endif

src/sys/memory.c

@@ -0,0 +1,2 @@
+#define CLIBS_SYS_MEMORY_IMPL
+#include <c-libs/sys/memory.h>

src/sys/syscall.s

@@ -1,4 +1,4 @@
-.global syscall5
+.global syscall5, syscall6
 
 syscall5:
     mov    %rdi, %rax /* %rax (syscall number)  = func param 1 (%rdi)    */
@@ -9,5 +9,16 @@ syscall5:
     mov    %r9,  %r8  /* %r8  (syscall param 5) = func param 6 (%r9)     */
     syscall           /* Enter a syscall (return value in %rax)          */
     ret               /* Return value is already in %rax, we can return. */
+
+syscall6:
+    mov    %rdi,    %rax /* %rax (syscall number)  = func param 1 (%rdi)    */
+    mov    %rsi,    %rdi /* %rdi (syscall param 1) = func param 2 (%rsi)    */
+    mov    %rdx,    %rsi /* %rsi (syscall param 2) = func param 3 (%rdx)    */
+    mov    %rcx,    %rdx /* %rdx (syscall param 3) = func param 4 (%rcx)    */
+    mov    %r8,     %r10 /* %r10 (syscall param 4) = func param 5 (%r8)     */
+    mov    %r9,     %r8  /* %r8  (syscall param 5) = func param 6 (%r9)     */
+    mov    8(%rsp), %r9  /* %r9 (syscall param 6) = stack-value             */
+    syscall              /* Enter a syscall (return value in %rax)          */
+    ret                  /* Return value is already in %rax, we can return. */
     
 .section .note.GNU-stack,"",@progbits