You can build project 2 on top of your project 1 submission or you can
start with a fresh copy. No code from project 1 is required for this
-assignment. The ``alarm clock'' functionality may be useful in later
-projects, but it is not strictly required.
+assignment. The ``alarm clock'' functionality may be useful in
+projects 3 and 4, but it is not strictly required.
@menu
* Project 2 Background::
user programs on top of the operating system, this is no longer true.
This project deals with consequences of the change.
-We allow more than one user program to run at a time. User
-programs are written and compiled to work under the illusion that they
-have the entire machine. This means that when you load and
-run multiple processes at a time, you must manage memory, scheduling,
-and other state correctly to maintain this illusion.
+We allow more than one process to run at a time. Each process has one
+thread (multithreaded processes are not supported). User programs are
+written under the illusion that they have the entire machine. This
+means that when you load and run multiple processes at a time, you must
+manage memory, scheduling, and other state correctly to maintain this
+illusion.
In the previous project, we compiled our test code directly into your
kernel, so we had to require certain specific function interfaces within
@deftypefn {System Call} bool create (const char *@var{file}, unsigned @var{initial_size})
Creates a new file called @var{file} initially @var{initial_size} bytes
in size. Returns true if successful, false otherwise.
+
+Consider implementing this function in terms of @func{filesys_create}.
@end deftypefn
@deftypefn {System Call} bool remove (const char *@var{file})
Deletes the file called @var{file}. Returns true if successful, false
otherwise.
+
+Consider implementing this function in terms of @func{filesys_remove}.
@end deftypefn
@deftypefn {System Call} int open (const char *@var{file})
is standard input (@code{stdin}), fd 1 is standard output
(@code{stdout}). These special file descriptors are valid as system
call arguments only as explicitly described below.
+
+Consider implementing this function in terms of @func{filesys_open}.
@end deftypefn
@deftypefn {System Call} int filesize (int @var{fd})
Returns the size, in bytes, of the file open as @var{fd}.
+
+Consider implementing this function in terms of @func{file_length}.
@end deftypefn
@deftypefn {System Call} int read (int @var{fd}, void *@var{buffer}, unsigned @var{size})
file), or -1 if the file could not be read (due to a condition other
than end of file). Fd 0 reads from the keyboard using
@func{kbd_getc}.
+
+Consider implementing this function in terms of @func{file_read}.
@end deftypefn
@deftypefn {System Call} int write (int @var{fd}, const void *@var{buffer}, unsigned @var{size})
Returns the number of bytes actually written, or -1 if the file could
not be written.
+Writing past end-of-file would normally extend the file, but file growth
+is not implemented by the basic file system. The expected behavior is
+to write as many bytes as possible up to end-of-file and return the
+actual number written, or -1 if no bytes could be written at all.
+
Fd 1 writes to the console. Your code to write to the console should
write all of @var{buffer} in one call to @func{putbuf}, at least as
long as @var{size} is not bigger than a few hundred bytes. Otherwise,
lines of text output by different processes may end up interleaved on
the console, confusing both human readers and our grading scripts.
+
+Consider implementing this function in terms of @func{file_write}.
@end deftypefn
@deftypefn {System Call} void seek (int @var{fd}, unsigned @var{position})
file will return an error.) These semantics are implemented in the
file system and do not require any special effort in system call
implementation.
+
+Consider implementing this function in terms of @func{file_seek}.
@end deftypefn
@deftypefn {System Call} unsigned tell (int @var{fd})
Returns the position of the next byte to be read or written in open
file @var{fd}, expressed in bytes from the beginning of the file.
+
+Consider implementing this function in terms of @func{file_tell}.
@end deftypefn
@deftypefn {System Call} void close (int @var{fd})
Closes file descriptor @var{fd}.
+
+Consider implementing this function in terms of @func{file_close}.
@end deftypefn
The file defines other syscalls. Ignore them for now. You will
the system call number is in the 32-bit word at the caller's stack
pointer, the first argument is in the 32-bit word at the next higher
address, and so on. The caller's stack pointer is accessible to
-@func{syscall_handler} as the @samp{esp} member of the @code{struct
-intr_frame} passed to it.
+@func{syscall_handler} as the @samp{esp} member of the
+@struct{intr_frame} passed to it. (@struct{intr_frame} is on the kernel
+stack.)
The 80@var{x}86 convention for function return values is to place them
in the @code{EAX} register. System calls that return a value can do
projects / pintos-anon / blobdiff