Start working on memory-mapped files.

First of all, change sys$mmap to take a struct SC_mmap_params since our
sycsall calling convention can't handle more than 3 arguments.

This exposed a bug in Syscall::invoke() needing to use clobber lists.
It was a bit confusing to debug. :^)

LibC/entry.cpp

@@ -17,21 +17,17 @@ extern "C" void __malloc_init();
 
 extern "C" int _start()
 {
-    __malloc_init();
-
     errno = 0;
-
     memset(__default_streams, 0, sizeof(__default_streams));
-
     __default_streams[0].fd = 0;
     stdin = &__default_streams[0];
-
     __default_streams[1].fd = 1;
     stdout = &__default_streams[1];
-
     __default_streams[2].fd = 2;
     stderr = &__default_streams[2];
 
+    __malloc_init();
+
     StringImpl::initializeGlobals();
 
     int status = 254;

LibC/grp.cpp

@@ -31,7 +31,7 @@ void setgrent()
             perror("open /etc/group");
         }
         assert(__grdb_stream);
-        __grdb_entry = (struct group_with_strings*)mmap(nullptr, getpagesize());
+        __grdb_entry = (struct group_with_strings*)mmap(nullptr, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
         set_mmap_name(__grdb_entry, getpagesize(), "setgrent");
     }
 }

LibC/mman.cpp

@@ -1,12 +1,14 @@
-#include "mman.h"
-#include "errno.h"
+#include <mman.h>
+#include <errno.h>
+#include <stdio.h>
 #include <Kernel/Syscall.h>
 
 extern "C" {
 
-void* mmap(void* addr, size_t size)
+void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset)
 {
-    int rc = Syscall::invoke(Syscall::SC_mmap, (dword)addr, (dword)size);
+    Syscall::SC_mmap_params params { (dword)addr, size, prot, flags, fd, offset };
+    int rc = Syscall::invoke(Syscall::SC_mmap, (dword)&params);
     __RETURN_WITH_ERRNO(rc, (void*)rc, (void*)-1);
 }
 

LibC/mman.h

@@ -3,9 +3,20 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
+#define MAP_SHARED 0x01
+#define MAP_PRIVATE 0x02
+#define MAP_FIXED 0x10
+#define MAP_ANONYMOUS 0x20
+#define MAP_ANON MAP_ANONYMOUS
+
+#define PROT_READ 0x1
+#define PROT_WRITE 0x2
+#define PROT_EXEC 0x4
+#define PROT_NONE 0x0
+
 __BEGIN_DECLS
 
-void* mmap(void*, size_t);
+void* mmap(void* addr, size_t, int prot, int flags, int fd, off_t);
 int munmap(void*, size_t);
 int set_mmap_name(void*, size_t, const char*);
 

LibC/pwd.cpp

@@ -32,7 +32,7 @@ void setpwent()
             perror("open /etc/passwd");
         }
         assert(__pwdb_stream);
-        __pwdb_entry = (struct passwd_with_strings*)mmap(nullptr, getpagesize());
+        __pwdb_entry = (struct passwd_with_strings*)mmap(nullptr, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
         set_mmap_name(__pwdb_entry, getpagesize(), "setpwent");
     }
 }

LibC/stdlib.cpp

@@ -18,7 +18,7 @@ static byte* endptr = nullptr;
 
 void __malloc_init()
 {
-    nextptr = (byte*)mmap(nullptr, mallocBudget);
+    nextptr = (byte*)mmap(nullptr, mallocBudget, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
     endptr = nextptr + mallocBudget;
     int rc = set_mmap_name(nextptr, mallocBudget, "malloc");
     if (rc < 0)