Support Linux ABI and (optionally) virtual memory

1 files changed, 57 insertions, 51 deletions

diff --git a/pk/file.c b/pk/file.c
index 195bcdc..ecc5f28 100644
--- a/pk/file.c
+++ b/pk/file.c
@@ -6,66 +6,52 @@
 #include "pk.h"
 #include "frontend.h"
 #include "pcr.h"
+#include "vm.h"
 
 #define MAX_FDS 32
-file_t* fds[MAX_FDS];
+static file_t* fds[MAX_FDS];
 #define MAX_FILES 32
-file_t files[MAX_FILES] = {[0 ... MAX_FILES-1] = {-1,{0}}};
+static file_t files[MAX_FILES] = {[0 ... MAX_FILES-1] = {-1,{0}}};
 file_t *stdout, *stdin, *stderr;
 
-static void file_incref(file_t* f)
+void file_incref(file_t* f)
 {
-  atomic_add(&f->refcnt,1);
+  atomic_add(&f->refcnt, 1);
 }
 
 void file_decref(file_t* f)
 {
-  if(atomic_add(&f->refcnt,-1) == 2)
+  if (atomic_add(&f->refcnt, -1) == 2)
   {
-    if(f->kfd != -1)
-    {
-      frontend_syscall(SYS_close,f->kfd,0,0,0);
-      f->kfd = -1;
-    }
-    atomic_add(&f->refcnt,-1); // I think this could just be atomic_set(..,0)
+    int kfd = f->kfd;
+    mb();
+    atomic_set(&f->refcnt, 0);
+
+    frontend_syscall(SYS_close, kfd, 0, 0, 0);
   }
 }
 
 static file_t* file_get_free()
 {
-  for(int i = 0; i < MAX_FILES; i++)
-  {
-    if(atomic_read(&files[i].refcnt) == 0)
-    {
-      if(atomic_add(&files[i].refcnt,1) == 0)
-      {
-        atomic_add(&files[i].refcnt,1);
-        return &files[i];
-      }
-      file_decref(&files[i]);
-    }
-  }
+  for (file_t* f = files; f < files + MAX_FILES; f++)
+    if (atomic_read(&f->refcnt) == 0 && atomic_cas(&f->refcnt, 0, 2) == 0)
+      return f;
   return NULL;
 }
 
-static int fd_get_free()
+int file_dup(file_t* f)
 {
-  for(int i = 0; i < MAX_FDS; i++)
-    if(fds[i] == NULL)
+  for (int i = 0; i < MAX_FDS; i++)
+  {
+    if (fds[i] == NULL && __sync_bool_compare_and_swap(&fds[i], 0, f))
+    {
+      file_incref(f);
       return i;
+    }
+  }
   return -1;
 }
 
-int file_dup(file_t* f)
-{
-  int fd = fd_get_free();
-  if(fd == -1)
-    return -1;
-  file_incref(f);
-  fds[fd] = f;
-  return fd;
-}
-
 void file_init()
 {
   stdin = file_get_free();
@@ -84,16 +70,28 @@ void file_init()
 
 file_t* file_get(int fd)
 {
-  return fd < 0 || fd >= MAX_FDS ? NULL : fds[fd];
+  file_t* f;
+  if (fd < 0 || fd >= MAX_FDS || (f = fds[fd]) == NULL)
+    return 0;
+
+  long old_cnt;
+  do {
+    old_cnt = atomic_read(&f->refcnt);
+    if (old_cnt == 0)
+      return 0;
+  } while (atomic_cas(&f->refcnt, old_cnt, old_cnt+1) != old_cnt);
+
+  return f;
 }
 
-sysret_t file_open(const char* fn, size_t len, int flags, int mode)
+sysret_t file_open(const char* fn, int flags, int mode)
 {
   file_t* f = file_get_free();
   if(!f)
     return (sysret_t){-1,ENOMEM};
 
-  sysret_t ret = frontend_syscall(SYS_open,(long)fn,len,flags,mode);
+  size_t fn_size = strlen(fn)+1;
+  sysret_t ret = frontend_syscall(SYS_open, (long)fn, fn_size, flags, mode);
   if(ret.result != -1)
   {
     f->kfd = ret.result;
@@ -108,39 +106,47 @@ sysret_t file_open(const char* fn, size_t len, int flags, int mode)
 int fd_close(int fd)
 {
   file_t* f = file_get(fd);
-  if(!f)
+  if (!f)
+    return -1;
+  int success = __sync_bool_compare_and_swap(&fds[fd], f, 0);
+  file_decref(f);
+  if (!success)
     return -1;
-  fds[fd] = NULL;
   file_decref(f);
   return 0;
 }
 
-sysret_t file_read(file_t* f, char* buf, size_t size)
+sysret_t file_read(file_t* f, void* buf, size_t size)
 {
-  return frontend_syscall(SYS_read,f->kfd,(long)buf,size,0);
+  populate_mapping(buf, size, PROT_WRITE);
+  return frontend_syscall(SYS_read, f->kfd, (uintptr_t)buf, size, 0);
 }
 
-sysret_t file_pread(file_t* f, char* buf, size_t size, off_t offset)
+sysret_t file_pread(file_t* f, void* buf, size_t size, off_t offset)
 {
-  return frontend_syscall(SYS_pread,f->kfd,(long)buf,size,offset);
+  populate_mapping(buf, size, PROT_WRITE);
+  return frontend_syscall(SYS_pread, f->kfd, (uintptr_t)buf, size, offset);
 }
 
-sysret_t file_write(file_t* f, const char* buf, size_t size)
+sysret_t file_write(file_t* f, const void* buf, size_t size)
 {
-  return frontend_syscall(SYS_write,f->kfd,(long)buf,size,0);
+  populate_mapping(buf, size, PROT_READ);
+  return frontend_syscall(SYS_write, f->kfd, (uintptr_t)buf, size, 0);
 }
 
-sysret_t file_pwrite(file_t* f, const char* buf, size_t size, off_t offset)
+sysret_t file_pwrite(file_t* f, const void* buf, size_t size, off_t offset)
 {
-  return frontend_syscall(SYS_pwrite,f->kfd,(long)buf,size,offset);
+  populate_mapping(buf, size, PROT_READ);
+  return frontend_syscall(SYS_pwrite, f->kfd, (uintptr_t)buf, size, offset);
 }
 
 sysret_t file_stat(file_t* f, struct stat* s)
 {
-  return frontend_syscall(SYS_fstat,f->kfd,(long)s,0,0);
+  populate_mapping(s, sizeof(*s), PROT_WRITE);
+  return frontend_syscall(SYS_fstat, f->kfd, (uintptr_t)s, 0, 0);
 }
 
 sysret_t file_lseek(file_t* f, size_t ptr, int dir)
 {
-  return frontend_syscall(SYS_lseek,f->kfd,ptr,dir,0);
+  return frontend_syscall(SYS_lseek, f->kfd, ptr, dir, 0);
 }