Interface---DRAFT---24 April 2001}. A draft of a revised version of
@bibref{SysV-ABI} which was never completed.
+@bibdfn{SUSv3}
+The Open Group, @uref{http://www.unix.org/single_unix_specification/,
+, Single UNIX Specification V3}, 2001.
+
@node Operating System Design References
@section Operating System Design References
We have also provided @command{pwd}, which is not so straightforward.
The @command{shell} program implements @command{cd} internally.
-The @code{pintos} @option{put} and @option{get} commands should now
+The @code{pintos} @option{extract} and @option{append} commands should now
accept full path names, assuming that the directories used in the
paths have already been created. This should not require any significant
extra effort on your part.
@option{-g} for @option{-p}.
Incidentally, these commands work by passing special commands
-@command{put} and @command{get} on the kernel's command line and copying
+@command{extract} and @command{append} on the kernel's command line and copying
to and from a special simulated ``scratch'' disk. If you're very
curious, you can look at the @command{pintos} script as well as
@file{filesys/fsutil.c} to learn the implementation details.
lib_SRC += lib/stdio.c # I/O library.
lib_SRC += lib/stdlib.c # Utility functions.
lib_SRC += lib/string.c # String functions.
-lib_SRC += lib/arithmetic.c
+lib_SRC += lib/arithmetic.c # 64-bit arithmetic for GCC.
+lib_SRC += lib/ustar.c # Unix standard tar format utilities.
# Kernel-specific library code.
lib/kernel_SRC = lib/kernel/debug.c # Debug helpers.
lib_SRC += lib/stdio.c # I/O library.
lib_SRC += lib/stdlib.c # Utility functions.
lib_SRC += lib/string.c # String functions.
-lib_SRC += lib/arithmetic.c
+lib_SRC += lib/arithmetic.c # 64-bit arithmetic for GCC.
+lib_SRC += lib/ustar.c # Unix standard tar format utilities.
# User level only library code.
lib/user_SRC = lib/user/debug.c # Debug helpers.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <ustar.h>
#include "filesys/directory.h"
#include "filesys/file.h"
#include "filesys/filesys.h"
PANIC ("%s: delete failed\n", file_name);
}
-/* Copies from the "scratch" disk, hdc or hd1:0 to file ARGV[1]
- in the file system.
-
- The current sector on the scratch disk must begin with the
- string "PUT\0" followed by a 32-bit little-endian integer
- indicating the file size in bytes. Subsequent sectors hold
- the file content.
-
- The first call to this function will read starting at the
- beginning of the scratch disk. Later calls advance across the
- disk. This disk position is independent of that used for
- fsutil_get(), so all `put's should precede all `get's. */
+/* Extracts a ustar-format tar archive from the scratch disk, hdc
+ or hd1:0, into the Pintos file system. */
void
-fsutil_put (char **argv)
+fsutil_extract (char **argv UNUSED)
{
static disk_sector_t sector = 0;
- const char *file_name = argv[1];
struct disk *src;
- struct file *dst;
- off_t size;
- void *buffer;
+ void *header, *data;
- printf ("Putting '%s' into the file system...\n", file_name);
+ /* Allocate buffers. */
+ header = malloc (DISK_SECTOR_SIZE);
+ data = malloc (DISK_SECTOR_SIZE);
+ if (header == NULL || data == NULL)
+ PANIC ("couldn't allocate buffers");
- /* Allocate buffer. */
- buffer = malloc (DISK_SECTOR_SIZE);
- if (buffer == NULL)
- PANIC ("couldn't allocate buffer");
-
- /* Open source disk and read file size. */
+ /* Open source disk. */
src = disk_get (1, 0);
if (src == NULL)
- PANIC ("couldn't open source disk (hdc or hd1:0)");
-
- /* Read file size. */
- disk_read (src, sector++, buffer);
- if (memcmp (buffer, "PUT", 4))
- PANIC ("%s: missing PUT signature on scratch disk", file_name);
- size = ((int32_t *) buffer)[1];
- if (size < 0)
- PANIC ("%s: invalid file size %d", file_name, size);
-
- /* Create destination file. */
- if (!filesys_create (file_name, size))
- PANIC ("%s: create failed", file_name);
- dst = filesys_open (file_name);
- if (dst == NULL)
- PANIC ("%s: open failed", file_name);
+ PANIC ("couldn't open scratch disk (hdc or hd1:0)");
- /* Do copy. */
- while (size > 0)
+ printf ("Extracting ustar archive from scratch disk into file system...\n");
+
+ for (;;)
{
- int chunk_size = size > DISK_SECTOR_SIZE ? DISK_SECTOR_SIZE : size;
- disk_read (src, sector++, buffer);
- if (file_write (dst, buffer, chunk_size) != chunk_size)
- PANIC ("%s: write failed with %"PROTd" bytes unwritten",
- file_name, size);
- size -= chunk_size;
+ const char *file_name;
+ const char *error;
+ enum ustar_type type;
+ int size;
+
+ /* Read and parse ustar header. */
+ disk_read (src, sector++, header);
+ error = ustar_parse_header (header, &file_name, &type, &size);
+ if (error != NULL)
+ PANIC ("bad ustar header in sector %"PRDSNu" (%s)", sector - 1, error);
+
+ if (type == USTAR_EOF)
+ {
+ /* End of archive. */
+ break;
+ }
+ else if (type == USTAR_DIRECTORY)
+ printf ("ignoring directory %s\n", file_name);
+ else if (type == USTAR_REGULAR)
+ {
+ struct file *dst;
+
+ printf ("Putting '%s' into the file system...\n", file_name);
+
+ /* Create destination file. */
+ if (!filesys_create (file_name, size))
+ PANIC ("%s: create failed", file_name);
+ dst = filesys_open (file_name);
+ if (dst == NULL)
+ PANIC ("%s: open failed", file_name);
+
+ /* Do copy. */
+ while (size > 0)
+ {
+ int chunk_size = (size > DISK_SECTOR_SIZE
+ ? DISK_SECTOR_SIZE
+ : size);
+ disk_read (src, sector++, data);
+ if (file_write (dst, data, chunk_size) != chunk_size)
+ PANIC ("%s: write failed with %d bytes unwritten",
+ file_name, size);
+ size -= chunk_size;
+ }
+
+ /* Finish up. */
+ file_close (dst);
+ }
}
- /* Finish up. */
- file_close (dst);
- free (buffer);
+ /* Erase the ustar header from the start of the disk, so that
+ the extraction operation is idempotent. We erase two blocks
+ because two blocks of zeros are the ustar end-of-archive
+ marker. */
+ printf ("Erasing ustar archive...\n");
+ memset (header, 0, DISK_SECTOR_SIZE);
+ disk_write (src, 0, header);
+ disk_write (src, 1, header);
+
+ free (data);
+ free (header);
}
-/* Copies file FILE_NAME from the file system to the scratch disk.
-
- The current sector on the scratch disk will receive "GET\0"
- followed by the file's size in bytes as a 32-bit,
- little-endian integer. Subsequent sectors receive the file's
- data.
+/* Copies file FILE_NAME from the file system to the scratch
+ disk, in ustar format.
The first call to this function will write starting at the
beginning of the scratch disk. Later calls advance across the
- disk. This disk position is independent of that used for
- fsutil_put(), so all `put's should precede all `get's. */
+ disk. This position is independent of that used for
+ fsutil_extract(), so `extract' should precede all
+ `append's. */
void
-fsutil_get (char **argv)
+fsutil_append (char **argv)
{
static disk_sector_t sector = 0;
struct disk *dst;
off_t size;
- printf ("Getting '%s' from the file system...\n", file_name);
+ printf ("Appending '%s' to ustar archive on scratch disk...\n", file_name);
/* Allocate buffer. */
buffer = malloc (DISK_SECTOR_SIZE);
if (dst == NULL)
PANIC ("couldn't open target disk (hdc or hd1:0)");
- /* Write size to sector 0. */
- memset (buffer, 0, DISK_SECTOR_SIZE);
- memcpy (buffer, "GET", 4);
- ((int32_t *) buffer)[1] = size;
+ /* Write ustar header to first sector. */
+ if (!ustar_make_header (file_name, USTAR_REGULAR, size, buffer))
+ PANIC ("%s: name too long for ustar format", file_name);
disk_write (dst, sector++, buffer);
-
+
/* Do copy. */
while (size > 0)
{
size -= chunk_size;
}
+ /* Write ustar end-of-archive marker, which is two consecutive
+ sectors full of zeros. Don't advance our position past
+ them, though, in case we have more files to append. */
+ memset (buffer, 0, DISK_SECTOR_SIZE);
+ disk_write (dst, sector, buffer);
+ disk_write (dst, sector, buffer + 1);
+
/* Finish up. */
file_close (src);
free (buffer);
void fsutil_ls (char **argv);
void fsutil_cat (char **argv);
void fsutil_rm (char **argv);
-void fsutil_put (char **argv);
-void fsutil_get (char **argv);
+void fsutil_extract (char **argv);
+void fsutil_append (char **argv);
#endif /* filesys/fsutil.h */
--- /dev/null
+#ifndef __LIB_PACKED_H
+#define __LIB_PACKED_H
+
+/* The "packed" attribute, when applied to a structure, prevents
+ GCC from inserting padding bytes between or after structure
+ members. It must be specified at the time of the structure's
+ definition, normally just after the closing brace. */
+#define PACKED __attribute__ ((packed))
+
+#endif /* lib/packed.h */
--- /dev/null
+#include <ustar.h>
+#include <limits.h>
+#include <packed.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Header for ustar-format tar archive. See the documentation of
+ the "pax" utility in [SUSv3] for the the "ustar" format
+ specification. */
+struct ustar_header
+ {
+ char name[100]; /* File name. Null-terminated if room. */
+ char mode[8]; /* Permissions as octal string. */
+ char uid[8]; /* User ID as octal string. */
+ char gid[8]; /* Group ID as octal string. */
+ char size[12]; /* File size in bytes as octal string. */
+ char mtime[12]; /* Modification time in seconds
+ from Jan 1, 1970, as octal string. */
+ char chksum[8]; /* Sum of octets in header as octal string. */
+ char typeflag; /* An enum ustar_type value. */
+ char linkname[100]; /* Name of link target.
+ Null-terminated if room. */
+ char magic[6]; /* "ustar\0" */
+ char version[2]; /* "00" */
+ char uname[32]; /* User name, always null-terminated. */
+ char gname[32]; /* Group name, always null-terminated. */
+ char devmajor[8]; /* Device major number as octal string. */
+ char devminor[8]; /* Device minor number as octal string. */
+ char prefix[155]; /* Prefix to file name.
+ Null-terminated if room. */
+ char padding[12]; /* Pad to 512 bytes. */
+ }
+PACKED;
+
+/* Returns the checksum for the given ustar format HEADER. */
+static unsigned int
+calculate_chksum (const struct ustar_header *h)
+{
+ const uint8_t *header = (const uint8_t *) h;
+ unsigned int chksum;
+ size_t i;
+
+ chksum = 0;
+ for (i = 0; i < USTAR_HEADER_SIZE; i++)
+ {
+ /* The ustar checksum is calculated as if the chksum field
+ were all spaces. */
+ const size_t chksum_start = offsetof (struct ustar_header, chksum);
+ const size_t chksum_end = chksum_start + sizeof h->chksum;
+ bool in_chksum_field = i >= chksum_start && i < chksum_end;
+ chksum += in_chksum_field ? ' ' : header[i];
+ }
+ return chksum;
+}
+
+/* Drop possibly dangerous prefixes from FILE_NAME and return the
+ stripped name. An archive with file names that start with "/"
+ or "../" could cause a naive tar extractor to write to
+ arbitrary parts of the file system, not just the destination
+ directory. We don't want to create such archives or be such a
+ naive extractor.
+
+ The return value can be a suffix of FILE_NAME or a string
+ literal. */
+static const char *
+strip_antisocial_prefixes (const char *file_name)
+{
+ while (*file_name == '/'
+ || !memcmp (file_name, "./", 2)
+ || !memcmp (file_name, "../", 3))
+ file_name = strchr (file_name, '/') + 1;
+ return *file_name == '\0' || !strcmp (file_name, "..") ? "." : file_name;
+}
+
+/* Composes HEADER as a USTAR_HEADER_SIZE (512)-byte archive
+ header in ustar format for a SIZE-byte file named FILE_NAME of
+ the given TYPE. The caller is responsible for writing the
+ header to a file or device.
+
+ If successful, returns true. On failure (due to an
+ excessively long file name), returns false. */
+bool
+ustar_make_header (const char *file_name, enum ustar_type type,
+ int size, char header[USTAR_HEADER_SIZE])
+{
+ struct ustar_header *h = (struct ustar_header *) header;
+
+ ASSERT (sizeof (struct ustar_header) == USTAR_HEADER_SIZE);
+ ASSERT (type == USTAR_REGULAR || type == USTAR_DIRECTORY);
+
+ /* Check file name. */
+ file_name = strip_antisocial_prefixes (file_name);
+ if (strlen (file_name) > 99)
+ {
+ printf ("%s: file name too long\n", file_name);
+ return false;
+ }
+
+ /* Fill in header except for final checksum. */
+ memset (h, 0, sizeof *h);
+ strlcpy (h->name, file_name, sizeof h->name);
+ snprintf (h->mode, sizeof h->mode, "%07o",
+ type == USTAR_REGULAR ? 0644 : 0755);
+ strlcpy (h->uid, "0000000", sizeof h->uid);
+ strlcpy (h->gid, "0000000", sizeof h->gid);
+ snprintf (h->size, sizeof h->size, "%011o", size);
+ snprintf (h->mtime, sizeof h->size, "%011o", 1136102400);
+ h->typeflag = type;
+ strlcpy (h->magic, "ustar", sizeof h->magic);
+ h->version[0] = h->version[1] = '0';
+ strlcpy (h->gname, "root", sizeof h->gname);
+ strlcpy (h->uname, "root", sizeof h->uname);
+
+ /* Compute and fill in final checksum. */
+ snprintf (h->chksum, sizeof h->chksum, "%07o", calculate_chksum (h));
+
+ return true;
+}
+
+/* Parses a SIZE-byte octal field in S in the format used by
+ ustar format. If successful, stores the field's value in
+ *VALUE and returns true; on failure, returns false.
+
+ ustar octal fields consist of a sequence of octal digits
+ terminated by a space or a null byte. The ustar specification
+ seems ambiguous as to whether these fields must be padded on
+ the left with '0's, so we accept any field that fits in the
+ available space, regardless of whether it fills the space. */
+static bool
+parse_octal_field (const char *s, size_t size, unsigned long int *value)
+{
+ size_t ofs;
+
+ *value = 0;
+ for (ofs = 0; ofs < size; ofs++)
+ {
+ char c = s[ofs];
+ if (c >= '0' && c <= '7')
+ {
+ if (*value > ULONG_MAX / 8)
+ {
+ /* Overflow. */
+ return false;
+ }
+ *value = c - '0' + *value * 8;
+ }
+ else if (c == ' ' || c == '\0')
+ {
+ /* End of field, but disallow completely empty
+ fields. */
+ return ofs > 0;
+ }
+ else
+ {
+ /* Bad character. */
+ return false;
+ }
+ }
+
+ /* Field did not end in space or null byte. */
+ return false;
+}
+
+/* Returns true if the CNT bytes starting at BLOCK are all zero,
+ false otherwise. */
+static bool
+is_all_zeros (const char *block, size_t cnt)
+{
+ while (cnt-- > 0)
+ if (*block++ != 0)
+ return false;
+ return true;
+}
+
+/* Parses HEADER as a ustar-format archive header for a regular
+ file or directory. If successful, stores the archived file's
+ name in *FILE_NAME (as a pointer into HEADER or a string
+ literal), its type in *TYPE, and its size in bytes in *SIZE,
+ and returns a null pointer. On failure, returns a
+ human-readable error message. */
+const char *
+ustar_parse_header (const char header[USTAR_HEADER_SIZE],
+ const char **file_name, enum ustar_type *type, int *size)
+{
+ const struct ustar_header *h = (const struct ustar_header *) header;
+ unsigned long int chksum, size_ul;
+
+ ASSERT (sizeof (struct ustar_header) == USTAR_HEADER_SIZE);
+
+ /* Detect end of archive. */
+ if (is_all_zeros (header, USTAR_HEADER_SIZE))
+ {
+ *file_name = NULL;
+ *type = USTAR_EOF;
+ *size = 0;
+ return NULL;
+ }
+
+ /* Validate ustar header. */
+ if (memcmp (h->magic, "ustar", 6))
+ return "not a ustar archive";
+ else if (h->version[0] != '0' || h->version[1] != '0')
+ return "invalid ustar version";
+ else if (!parse_octal_field (h->chksum, sizeof h->chksum, &chksum))
+ return "corrupt chksum field";
+ else if (chksum != calculate_chksum (h))
+ return "checksum mismatch";
+ else if (h->name[sizeof h->name - 1] != '\0' || h->prefix[0] != '\0')
+ return "file name too long";
+ else if (h->typeflag != USTAR_REGULAR && h->typeflag != USTAR_DIRECTORY)
+ return "unimplemented file type";
+ if (h->typeflag == USTAR_REGULAR)
+ {
+ if (!parse_octal_field (h->size, sizeof h->size, &size_ul))
+ return "corrupt file size field";
+ else if (size_ul > INT_MAX)
+ return "file too large";
+ }
+ else
+ size_ul = 0;
+
+ /* Success. */
+ *file_name = strip_antisocial_prefixes (h->name);
+ *type = h->typeflag;
+ *size = size_ul;
+ return NULL;
+}
+
--- /dev/null
+#ifndef __LIB_USTAR_H
+#define __LIB_USTAR_H
+
+/* Support for the standard Posix "ustar" format. See the
+ documentation of the "pax" utility in [SUSv3] for the the
+ "ustar" format specification. */
+
+#include <stdbool.h>
+
+/* Type of a file entry in an archive.
+ The values here are the bytes that appear in the file format.
+ Only types of interest to Pintos are listed here. */
+enum ustar_type
+ {
+ USTAR_REGULAR = '0', /* Ordinary file. */
+ USTAR_DIRECTORY = '5', /* Directory. */
+ USTAR_EOF = -1 /* End of archive (not an official value). */
+ };
+
+/* Size of a ustar archive header, in bytes. */
+#define USTAR_HEADER_SIZE 512
+
+bool ustar_make_header (const char *file_name, enum ustar_type,
+ int size, char header[USTAR_HEADER_SIZE]);
+const char *ustar_parse_header (const char header[USTAR_HEADER_SIZE],
+ const char **file_name,
+ enum ustar_type *, int *size);
+
+#endif /* lib/ustar.h */
Creates a tar archive. */
+#include <ustar.h>
#include <syscall.h>
#include <stdio.h>
#include <string.h>
int archive_fd, bool *write_error);
static bool archive_directory (char file_name[], size_t file_name_size,
int file_fd, int archive_fd, bool *write_error);
-static bool write_header (const char *file_name,
- char type_flag, int size, unsigned mode,
+static bool write_header (const char *file_name, enum ustar_type, int size,
int archive_fd, bool *write_error);
static bool do_write (int fd, const char *buffer, int size, bool *write_error);
bool success = true;
int file_size = filesize (file_fd);
- if (!write_header (file_name, '0', file_size, 0644, archive_fd, write_error))
+ if (!write_header (file_name, USTAR_REGULAR, file_size,
+ archive_fd, write_error))
return false;
while (file_size > 0)
return false;
}
- if (!write_header (file_name, '5', 0, 0755, archive_fd, write_error))
+ if (!write_header (file_name, USTAR_DIRECTORY, 0, archive_fd, write_error))
return false;
file_name[dir_len] = '/';
}
static bool
-write_header (const char *file_name,
- char type_flag, int size, unsigned mode,
+write_header (const char *file_name, enum ustar_type type, int size,
int archive_fd, bool *write_error)
{
static char header[512];
- unsigned chksum;
- size_t i;
-
- memset (header, 0, sizeof header);
-
- /* Drop confusing and possibly dangerous prefixes from
- FILE_NAME. */
- while (*file_name == '/'
- || !memcmp (file_name, "./", 2)
- || !memcmp (file_name, "../", 3))
- file_name = strchr (file_name, '/') + 1;
- if (*file_name == '\0')
- {
- /* Dropped *everything* from FILE_NAME.
- Should only be possible for a directory. */
- ASSERT (type_flag == '5');
- return true;
- }
- else if (strlen (file_name) > 99)
- {
- printf ("%s: file name too long\n", file_name);
- return false;
- }
-
- /* Fill in header except for final checksum. */
- strlcpy (header, file_name, 100); /* name */
- snprintf (header + 100, 8, "%07o", mode); /* mode */
- strlcpy (header + 108, "0000000", 8); /* uid */
- strlcpy (header + 116, "0000000", 8); /* gid */
- snprintf (header + 124, 12, "%011o", size); /* size */
- snprintf (header + 136, 12, "%011o", 1136102400); /* mtime (2006-01-01) */
- memset (header + 148, ' ', 8); /* chksum */
- header[156] = type_flag; /* typeflag */
- strlcpy (header + 257, "ustar", 6); /* magic */
- strlcpy (header + 263, "00", 3); /* version */
-
- /* Compute and fill in final checksum. */
- chksum = 0;
- for (i = 0; i < 512; i++)
- chksum += (uint8_t) header[i];
- snprintf (header + 148, 8, "%07o", chksum);
-
- /* Write header. */
- return do_write (archive_fd, header, 512, write_error);
+ return (ustar_make_header (file_name, type, size, header)
+ && do_write (archive_fd, header, 512, write_error));
}
static bool
$size = 0 if $typeflag eq '5';
# Store content.
+ $name =~ s%^(/|\./|\.\./)*%%; # Strip leading "/", "./", "../".
+ $name = '' if $name eq '.' || $name eq '..';
if (exists $content{$name}) {
fail "$archive: contains multiple entries for $name\n";
}
if ($typeflag eq '5') {
- $content{$name} = 'directory';
+ $content{$name} = 'directory' if $name ne '';
} else {
+ fail "$archive: contains file with empty name\n" if $name eq '';
my ($position) = sysseek (ARCHIVE, 0, SEEK_CUR);
$content{$name} = [$archive, $position, $size];
sysseek (ARCHIVE, int (($size + 511) / 512) * 512, SEEK_CUR);
{"ls", 1, fsutil_ls},
{"cat", 2, fsutil_cat},
{"rm", 2, fsutil_rm},
- {"put", 2, fsutil_put},
- {"get", 2, fsutil_get},
+ {"extract", 1, fsutil_extract},
+ {"append", 2, fsutil_append},
#endif
{NULL, 0, NULL},
};
" cat FILE Print FILE to the console.\n"
" rm FILE Delete FILE.\n"
"Use these actions indirectly via `pintos' -g and -p options:\n"
- " put FILE Put FILE into file system from scratch disk.\n"
- " get FILE Get FILE from file system into scratch disk.\n"
+ " extract Untar from scratch disk into file system.\n"
+ " append FILE Append FILE to tar file on scratch disk.\n"
#endif
"\nOptions:\n"
" -h Print this help message and power off.\n"
\f
# Prepare the scratch disk for gets and puts.
sub prepare_scratch_disk {
- # Copy the files to put onto the scratch disk.
- put_scratch_file ($_->[0]) foreach @puts;
+ if (@puts) {
+ # Write ustar header and data for each file.
+ put_scratch_file ($_->[0],
+ defined $_->[1] ? $_->[1] : $_->[0])
+ foreach @puts;
+
+ # Write end-of-archive marker.
+ print { $disks{SCRATCH}{HANDLE} } "\0" x 1024;
+ }
# Make sure the scratch disk is big enough to get big files.
extend_disk ($disks{SCRATCH}, @gets * 1024 * 1024) if @gets;
my ($ok) = 1;
foreach my $get (@gets) {
my ($name) = defined ($get->[1]) ? $get->[1] : $get->[0];
- $ok &&= get_scratch_file ($name);
- if (!$ok) {
+ my ($error) = get_scratch_file ($name);
+ if ($error) {
+ print STDERR "getting $name failed ($error)\n";
die "$name: unlink: $!\n" if !unlink ($name) && !$!{ENOENT};
+ $ok = 0;
}
}
}
-# put_scratch_file($file).
+# mk_ustar_field($number, $size)
+#
+# Returns $number in a $size-byte numeric field in the format used by
+# the standard ustar archive header.
+sub mk_ustar_field {
+ my ($number, $size) = @_;
+ my ($len) = $size - 1;
+ my ($out) = sprintf ("%0${len}o", $number) . "\0";
+ die "$number: too large for $size-byte octal ustar field\n"
+ if length ($out) != $size;
+ return $out;
+}
+
+# calc_ustar_chksum($s)
+#
+# Calculates and returns the ustar checksum of 512-byte ustar archive
+# header $s.
+sub calc_ustar_chksum {
+ my ($s) = @_;
+ die if length ($s) != 512;
+ substr ($s, 148, 8, ' ' x 8);
+ return unpack ("%32a*", $s);
+}
+
+# put_scratch_file($src_file_name, $dst_file_name).
#
-# Copies $file into the scratch disk.
+# Copies $src_file_name into the scratch disk for extraction as
+# $dst_file_name.
sub put_scratch_file {
- my ($put_file_name) = @_;
+ my ($src_file_name, $dst_file_name) = @_;
my ($disk_handle, $disk_file_name) = open_disk ($disks{SCRATCH});
- print "Copying $put_file_name into $disk_file_name...\n";
+ print "Copying $src_file_name to scratch partition...\n";
+
+ # ustar format supports up to 100 characters for a file name, and
+ # even longer names given some common properties, but our code in
+ # the Pintos kernel only supports at most 99 characters.
+ die "$dst_file_name: name too long (max 99 characters)\n"
+ if length ($dst_file_name) > 99;
- # Write metadata sector, which consists of a 4-byte signature
- # followed by the file size.
- stat $put_file_name or die "$put_file_name: stat: $!\n";
+ # Compose and write ustar header.
+ stat $src_file_name or die "$src_file_name: stat: $!\n";
my ($size) = -s _;
- my ($metadata) = pack ("a4 V x504", "PUT\0", $size);
- write_fully ($disk_handle, $disk_file_name, $metadata);
+ my ($header) = (pack ("a100", $dst_file_name) # name
+ . mk_ustar_field (0644, 8) # mode
+ . mk_ustar_field (0, 8) # uid
+ . mk_ustar_field (0, 8) # gid
+ . mk_ustar_field ($size, 12) # size
+ . mk_ustar_field (1136102400, 12) # mtime
+ . (' ' x 8) # chksum
+ . '0' # typeflag
+ . ("\0" x 100) # linkname
+ . "ustar\0" # magic
+ . "00" # version
+ . "root" . ("\0" x 28) # uname
+ . "root" . ("\0" x 28) # gname
+ . "\0" x 8 # devmajor
+ . "\0" x 8 # devminor
+ . ("\0" x 155)) # prefix
+ . "\0" x 12; # pad to 512 bytes
+ substr ($header, 148, 8) = mk_ustar_field (calc_ustar_chksum ($header), 8);
+ write_fully ($disk_handle, $disk_file_name, $header);
# Copy file data.
my ($put_handle);
- sysopen ($put_handle, $put_file_name, O_RDONLY)
- or die "$put_file_name: open: $!\n";
- copy_file ($put_handle, $put_file_name, $disk_handle, $disk_file_name,
+ sysopen ($put_handle, $src_file_name, O_RDONLY)
+ or die "$src_file_name: open: $!\n";
+ copy_file ($put_handle, $src_file_name, $disk_handle, $disk_file_name,
$size);
+ die "$src_file_name: changed size while being read\n"
+ if $size != -s $put_handle;
close ($put_handle);
# Round up disk data to beginning of next sector.
print "Copying $get_file_name out of $disk_file_name...\n";
- # Read metadata sector, which has a 4-byte signature followed by
- # the file size.
- my ($metadata) = read_fully ($disk_handle, $disk_file_name, 512);
- my ($signature, $size) = unpack ("a4 V", $metadata);
- (print STDERR "bad signature on scratch disk--did Pintos run fail?\n"),
- return 0
- if $signature ne "GET\0";
+ # Read ustar header sector.
+ my ($header) = read_fully ($disk_handle, $disk_file_name, 512);
+ return "scratch disk tar archive ends unexpectedly"
+ if $header eq ("\0" x 512);
+
+ # Verify magic numbers.
+ return "corrupt ustar signature" if substr ($header, 257, 6) ne "ustar\0";
+ return "invalid ustar version" if substr ($header, 263, 2) ne '00';
+
+ # Verify checksum.
+ my ($chksum) = oct (unpack ("Z*", substr ($header, 148, 8)));
+ my ($correct_chksum) = calc_ustar_chksum ($header);
+ return "checksum mismatch" if $chksum != $correct_chksum;
+
+ # Get type.
+ my ($typeflag) = substr ($header, 156, 1);
+ return "not a regular file" if $typeflag ne '0' && $typeflag ne "\0";
+
+ # Get size.
+ my ($size) = oct (unpack ("Z*", substr ($header, 124, 12)));
+ return "bad size $size\n" if $size < 0;
# Copy file data.
my ($get_handle);
read_fully ($disk_handle, $disk_file_name, 512 - $size % 512)
if $size % 512;
- return 1;
+ return 0;
}
\f
# Prepares the arguments to pass to the Pintos kernel,
my (@args);
push (@args, shift (@kernel_args))
while @kernel_args && $kernel_args[0] =~ /^-/;
- push (@args, 'put', defined $_->[1] ? $_->[1] : $_->[0]) foreach @puts;
+ push (@args, 'extract') if @puts;
push (@args, @kernel_args);
- push (@args, 'get', $_->[0]) foreach @gets;
+ push (@args, 'append', $_->[0]) foreach @gets;
write_cmd_line ($disks{OS}, @args);
}
projects / pintos-anon / commitdiff