feat(sys): add malloc

CMakeLists.txt

@@ -17,11 +17,22 @@ 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
+  ${CMAKE_CURRENT_SOURCE_DIR}/src/sys/memory.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)
+  nolibc
+  PRIVATE -fno-asynchronous-unwind-tables -fno-unwind-tables
+          -fno-stack-protector -ffunction-sections -fdata-sections -fno-builtin)
 target_link_options(
   nolibc
   PRIVATE
@@ -50,7 +61,7 @@ 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}

app/entry.s

@@ -1,29 +0,0 @@
-.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
-
-syscall5:
-    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)     */
-    syscall           /* Enter a syscall (return value in %rax)          */
-    ret               /* Return value is already in %rax, we can return. */
-    
-.section .note.GNU-stack,"",@progbits

app/nolibc.c

@@ -1,18 +1,19 @@
-void *syscall5(void *number, void *arg1, void *arg2, void *arg3, void *arg4,
-               void *arg5);
+#include <c-libs/sys/memory.h>
+#include <c-libs/sys/syscall.h>
 
-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 */
-  );
+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

@@ -0,0 +1,42 @@
+#ifndef CLIBS_SYS_SYSCALL_H
+#define CLIBS_SYS_SYSCALL_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
+
+__s64 write(int fd, void const *data, __u64 nbytes) {
+  return (__s64)syscall5((void *)__NR_write, (void *)(__u64)fd, (void *)data,
+                         (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/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

src/sys/memory.c

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

src/sys/syscall.c

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

src/sys/syscall.s

@@ -0,0 +1,24 @@
+.global syscall5, syscall6
+
+syscall5:
+    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)     */
+    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