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-rw-r--r--toys/other/losetup.c190
1 files changed, 190 insertions, 0 deletions
diff --git a/toys/other/losetup.c b/toys/other/losetup.c
new file mode 100644
index 00000000..aa62222c
--- /dev/null
+++ b/toys/other/losetup.c
@@ -0,0 +1,190 @@
+/* losetup.c - Loopback setup
+ *
+ * Copyright 2012 Rob Landley <rob@landley.net>
+ *
+ * No standard. (Sigh.)
+
+USE_LOSETUP(NEWTOY(losetup, ">2S(sizelimit)#s(show)ro#j:fdca[!afj]", TOYFLAG_SBIN))
+
+config LOSETUP
+ bool "losetup"
+ default y
+ help
+ usage: losetup [-cdrs] [-o OFFSET] [-S SIZE] {-d DEVICE...|-j FILE|-af|{DEVICE FILE}}
+
+ Associate a loopback device with a file, or show current file (if any)
+ associated with a loop device.
+
+ Instead of a device:
+ -a Iterate through all loopback devices
+ -f Find first unused loop device (may create one)
+ -j Iterate through all loopback devices associated with FILE
+
+ existing:
+ -c Check capacity (file size changed)
+ -d Detach loopback device
+
+ new:
+ -s Show device name (alias --show)
+ -o Start assocation at OFFSET into FILE
+ -r Read only
+ -S Limit SIZE of loopback association (alias --sizelimit)
+*/
+
+#define FOR_losetup
+#include "toys.h"
+#include <linux/loop.h>
+
+GLOBALS(
+ char *jfile;
+ long offset;
+ long size;
+
+ int openflags;
+ dev_t jdev;
+ ino_t jino;
+)
+
+/*
+todo: basic /dev file association
+ associate DEV FILE
+ #-a
+ cdfjosS
+ allocate new loop device:
+ /dev/loop-control
+ https://lkml.org/lkml/2011/7/26/148
+*/
+
+// -f: *device is NULL
+
+// Perform requested operation on one device. Returns 1 if handled, 0 if error
+static void loopback_setup(char *device, char *file)
+{
+ struct loop_info64 *loop = (void *)(toybuf+32);
+ int rc = 0, lfd = -1, ffd;
+ unsigned flags = toys.optflags;
+
+ // Open file (ffd) and loop device (lfd)
+
+ if (file) ffd = xopen(file, TT.openflags);
+ if (!device) {
+ int i, cfd = open("/dev/loop-control", O_RDWR);
+
+ // We assume /dev is devtmpfs so device creation has no lag. Otherwise
+ // just preallocate loop devices and stay within them.
+
+ // mount -o loop depends on found device being at the start of toybuf.
+ if (cfd != -1) {
+ if (0 <= (i = ioctl(cfd, LOOP_CTL_GET_FREE)))
+ sprintf(device = toybuf, "/dev/loop%d", i);
+ close(cfd);
+ }
+ }
+
+ if (device) lfd = open(device, TT.openflags);
+
+ // Stat the loop device to see if there's a current association.
+ memset(loop, 0, sizeof(struct loop_info64));
+ if (-1 == lfd || ioctl(lfd, LOOP_GET_STATUS64, loop)) {
+ if (errno == ENXIO && (flags & (FLAG_a|FLAG_j))) return;
+ if (errno != ENXIO || !file) {
+ perror_msg("%s", device ? device : "-f");
+ rc = 1;
+ goto done;
+ }
+ }
+
+ // Skip -j filtered devices
+ if (TT.jfile && (loop->lo_device != TT.jdev || loop->lo_inode != TT.jino))
+ goto done;
+
+ // Check size of file or delete existing association
+ if (flags & (FLAG_c|FLAG_d)) {
+ if (ioctl(lfd, (flags & FLAG_c) ? LOOP_SET_CAPACITY : LOOP_CLR_FD, 0)) {
+ perror_msg("%s", device);
+ rc = 1;
+ goto done;
+ }
+ // Associate file with this device?
+ } else if (file) {
+ char *s = xrealpath(file);
+
+ if (ioctl(lfd, LOOP_SET_FD, ffd)) perror_exit("%s=%s", device, file);
+ loop->lo_offset = TT.offset;
+ loop->lo_sizelimit = TT.size;
+ strncpy((char *)loop->lo_file_name, s, LO_NAME_SIZE);
+ s[LO_NAME_SIZE-1] = 0;
+ if (ioctl(lfd, LOOP_SET_STATUS64, loop)) perror_exit("%s=%s", device, file);
+ if (flags & FLAG_s) printf("%s", device);
+ free(s);
+ } else if (flags & FLAG_f) printf("%s", device);
+ else {
+ xprintf("%s: [%04llx]:%llu (%s)", device, loop->lo_device, loop->lo_inode,
+ loop->lo_file_name);
+ if (loop->lo_offset) xprintf(", offset %llu", loop->lo_offset);
+ if (loop->lo_sizelimit) xprintf(", sizelimit %llu", loop->lo_sizelimit);
+ xputc('\n');
+ }
+
+done:
+ if (file) close(ffd);
+ if (lfd != -1) close(lfd);
+ toys.exitval |= rc;
+}
+
+// Perform an action on all currently existing loop devices
+static int dash_a(struct dirtree *node)
+{
+ char *s = node->name;
+
+ // Initial /dev node needs to recurse down one level, then only loop[0-9]*
+ if (*s == '/') return DIRTREE_RECURSE;
+ if (strncmp(s, "loop", 4) || !isdigit(s[4])) return 0;
+
+ s = dirtree_path(node, 0);
+ loopback_setup(s, 0);
+ free(s);
+
+ return 0;
+}
+
+void losetup_main(void)
+{
+ char **s;
+
+ TT.openflags = (toys.optflags & FLAG_r) ? O_RDONLY : O_RDWR;
+
+ if (TT.jfile) {
+ struct stat st;
+
+ xstat(TT.jfile, &st);
+ TT.jdev = st.st_dev;
+ TT.jino = st.st_ino;
+ }
+
+ // With just device, display current association
+ // -a, -f substitute for device
+ // -j substitute for device
+
+ // new association: S size o offset rs - need a file
+ // existing association: cd
+
+ // -f(dc FILE)
+
+ if (toys.optflags & FLAG_f) {
+ if (toys.optc > 1) perror_exit("max 1 arg");
+ loopback_setup(NULL, *toys.optargs);
+ } else if (toys.optflags & (FLAG_a|FLAG_j)) {
+ if (toys.optc) error_exit("bad args");
+ dirtree_read("/dev", dash_a);
+ // Do we need one DEVICE argument?
+ } else {
+ char *file = (toys.optflags & (FLAG_d|FLAG_c)) ? NULL : toys.optargs[1];
+
+ if (!toys.optc || (file && toys.optc>1)) {
+ if (CFG_HELP) toys.exithelp++;
+ perror_exit("needs 1 arg");
+ }
+ for (s = toys.optargs; *s; s++) loopback_setup(*s, file);
+ }
+}