[FS] Pipes

init/init.c

@@ -8,8 +8,27 @@ int main(int argc, char **argv)
   (void) argv;
 
 
-  FILE *fp = fopen("/dev/debug", "w");
+  int fd[2];
-  fprintf(fp, "Hello, filesystem!\n");
+  pipe(fd);
+
+  pid_t childpid = fork();
+
+  if(childpid)
+  {
+    printf("I am parent!\n");
+    close(fd[1]);
+    write(fd[0], "Hi, pipe!\n", 10);
+    close(fd[0]);
+  }
+  else
+  {
+    printf("I am child!\n");
+    close(fd[0]);
+    char buffer[255];
+    read(fd[1], buffer, 255);
+    printf("Received string: %s\n", buffer);
+    close(fd[1]);
+  }
 
 
   for(;;);

kernel/fs/pipe.c

@@ -0,0 +1,150 @@
+#include <vfs.h>
+#include <stdint.h>
+#include <sync.h>
+#include <mem.h>
+#include <debug.h>
+#include <scheduler.h>
+
+#define PIPE_SIZE 0x1000
+
+struct pipe_data
+{
+  uint8_t *buffer;
+  lock_t lock;
+  uint64_t size;
+  uint64_t readers;
+  uint64_t writers;
+  uint64_t read_pos;
+  uint64_t write_pos;
+  file_t *reader;
+  file_t *writer;
+};
+
+int pipe_open(file_t *file, uint64_t flags)
+{
+  (void) flags;
+  struct pipe_data *d = file->data;
+  spin_lock(&d->lock);
+  if(file == d->reader)
+    d->readers ++;
+  else
+    d->writers ++;
+  spin_unlock(&d->lock);
+  return 0;
+}
+
+int pipe_close(file_t *file)
+{
+  debug("Closing pipe\n");
+  struct pipe_data *d = file->data;
+  spin_lock(&d->lock);
+  if(file == d->reader)
+    d->readers --;
+  else
+    d->writers --;
+  if((!d->readers) && !(d->writers))
+  {
+    debug("Freeing pipe\n");
+    kfree(d);
+    kfree(file);
+  } else {
+    spin_unlock(&d->lock);
+  }
+  return 0;
+}
+
+size_t pipe_read(file_t *file, void *buffer, size_t nbyte, size_t offset)
+{
+  (void) offset;
+  struct pipe_data *d = file->data;
+  uint8_t *buf = buffer;
+
+  spin_lock(&d->lock);
+  while(d->read_pos >= d->write_pos)
+  {
+    spin_unlock(&d->lock);
+    schedule();
+    spin_lock(&d->lock);
+  }
+
+  uint64_t bytes = d->write_pos - d->read_pos;
+  if(bytes > nbyte) bytes = nbyte;
+
+  uint64_t buf_pos = d->read_pos % d->size;
+  uint64_t n = d->size - buf_pos;
+  if(n > bytes) n = bytes;
+
+  memcpy(buf, &d->buffer[buf_pos], n);
+  if(bytes-n)
+    memcpy(&buf[n], d->buffer, bytes-n);
+
+  d->read_pos += bytes;
+
+  spin_unlock(&d->lock);
+  return bytes;
+}
+
+size_t pipe_write(file_t *file, void *buffer, size_t nbyte, size_t offset)
+{
+  (void) offset;
+  struct pipe_data *d = file->data;
+  uint8_t *buf = buffer;
+  uint64_t written = 0;
+
+  spin_lock(&d->lock);
+  while(nbyte)
+  {
+    while(d->write_pos >= d->read_pos + d->size)
+    {
+      spin_unlock(&d->lock);
+      schedule();
+      spin_lock(&d->lock);
+    }
+
+    uint64_t bytes = d->size - (d->write_pos - d->read_pos);
+    if(bytes > nbyte) bytes = nbyte;
+
+    uint64_t buf_pos = d->write_pos % d->size;
+    uint64_t n = d->size - buf_pos;
+    if(n > bytes) n = bytes;
+
+    memcpy(&d->buffer[buf_pos], &buf[written], n);
+    if(bytes-n)
+      memcpy(d->buffer, &buf[written + n], bytes-n);
+
+    nbyte -= bytes;
+    d->write_pos += bytes;
+    written += bytes;
+  }
+
+  spin_unlock(&d->lock);
+  return written;
+}
+
+fs_driver_t pipe_writer = {
+  .open = pipe_open,
+  .close = pipe_close,
+  .write = pipe_write,
+};
+fs_driver_t pipe_reader = {
+  .open = pipe_open,
+  .close = pipe_close,
+  .read = pipe_read,
+};
+
+int pipe(file_t **r, file_t **w)
+{
+  *r = kcalloc(1, sizeof(file_t));
+  *w = kcalloc(1, sizeof(file_t));
+  struct pipe_data *data = (*r)->data = (*w)->data = kcalloc(1, sizeof(struct pipe_data));
+  (*r)->driver = &pipe_reader;
+  (*w)->driver = &pipe_writer;
+
+  data->buffer = kcalloc(1, PIPE_SIZE);
+  data->size = PIPE_SIZE;
+  spin_unlock(&data->lock);
+  data->reader = *r;
+  data->writer = *w;
+
+  return 0;
+}

kernel/include/syscall.h

@@ -46,6 +46,7 @@ SYSCALL_DECL(read);
 SYSCALL_DECL(write);
 SYSCALL_DECL(isatty);
 SYSCALL_DECL(seek);
+SYSCALL_DECL(pipe);
 
 SYSCALL_DECL(brk);
 

kernel/include/vfs.h

@@ -59,3 +59,4 @@ void fs_umount(const char *path);
 file_t *fs_namef(const char *path);
 
 file_t debug_file;
+int pipe(file_t **reader, file_t **writer);

kernel/syscall/sys_fs.c

@@ -78,3 +78,59 @@ SYSCALL_DEF(seek)
 
   return p->fp[fd].pos;
 }
+
+SYSCALL_DEF(pipe)
+{
+  SYSCALL_INIT(int *, fd);
+  process_t *p = get_current_process();
+  file_t *r, *w;
+  pipe(&r, &w);
+
+  fd[0] = -1;
+  fd[1] = -1;
+
+  int i;
+  for(i = 0; i < PROC_NUMFP; i++)
+  {
+    if(!p->fp[i].file)
+    {
+      p->fp[i].file = fs_get(w);
+      fs_open(w,0);
+      fd[0] = i;
+      break;
+    }
+  }
+  if(i == PROC_NUMFP)
+    goto pipe_fail;
+  for(i = 0; i < PROC_NUMFP; i++)
+  {
+    if(!p->fp[i].file)
+    {
+      p->fp[i].file = fs_get(r);
+      fs_open(r,0);
+      fd[1] = i;
+      break;
+    }
+  }
+  if(i == PROC_NUMFP)
+    goto pipe_fail;
+
+  return 0;
+
+pipe_fail:
+  if(r)
+    kfree(r);
+  if(w)
+    kfree(w);
+  if(fd[0] != -1)
+  {
+    fs_put(p->fp[fd[0]].file);
+    p->fp[fd[0]].file = 0;
+  }
+  if(fd[1] != -1)
+  {
+    fs_put(p->fp[fd[1]].file);
+    p->fp[fd[1]].file = 0;
+  }
+  return -1;
+}

kernel/syscall/syscall.c

@@ -62,6 +62,7 @@ void syscall_init()
     SYSCALL_REGISTER(write, SYS_WRITE);
     SYSCALL_REGISTER(isatty, SYS_ISATTY);
     SYSCALL_REGISTER(seek, SYS_SEEK);
+    SYSCALL_REGISTER(pipe, SYS_PIPE);
 
     SYSCALL_REGISTER(brk, SYS_BRK);
 

libc/file_io.c

@@ -69,3 +69,9 @@ SYSCALL_DEF(ioctl)
   kernel_debug("==> IOCTL - unsupported request:%lx\n", request);
   return -1;
 }
+
+SYSCALL_DEF(pipe)
+{
+  SYSCALL_INIT(int *, fd);
+  return kernel_syscall(SYS_PIPE, fd);
+}

libc/syscall_num.h

@@ -14,3 +14,5 @@
 #define SYS_FORK  0x008
 #define SYS_EXIT  0x009
 #define SYS_WAIT  0x00A
+
+#define SYS_PIPE 0x00B