3 files changed, 148 insertions, 73 deletions

diff --git a/libbb/Config.src b/libbb/Config.src
index 66a3ffa23..b980f19a9 100644
--- a/libbb/Config.src
+++ b/libbb/Config.src
@@ -369,3 +369,25 @@ config UNICODE_PRESERVE_BROKEN
         For example, this means that entering 'l', 's', ' ', 0xff, [Enter]
         at shell prompt will list file named 0xff (single char name
         with char value 255), not file named '?'.
+
+choice
+        prompt "Use LOOP_CONFIGURE for losetup and loop mounts"
+        default TRY_LOOP_CONFIGURE
+        help
+        LOOP_CONFIGURE is added to Linux 5.8
+        https://lwn.net/Articles/820408/
+        This allows userspace to completely setup a loop device with a single
+        ioctl, removing the in-between state where the device can be partially
+        configured - eg the loop device has a backing file associated with it,
+        but is reading from the wrong offset.
+
+config LOOP_CONFIGURE
+        bool "use LOOP_CONFIGURE, needs kernel >= 5.8"
+
+config NO_LOOP_CONFIGURE
+        bool "use LOOP_SET_FD + LOOP_SET_STATUS"
+
+config TRY_LOOP_CONFIGURE
+        bool "try LOOP_CONFIGURE, fall back to LOOP_SET_FD + LOOP_SET_STATUS"
+
+endchoice
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index b4950688e..bee423553 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -249,14 +249,6 @@ static void get_user_strings(void)
         }
 }
 
-static const char *get_username_str(void)
-{
-        if (!got_user_strings)
-                get_user_strings();
-        return user_buf ? user_buf : "";
-        /* btw, bash uses "I have no name!" string if uid has no entry */
-}
-
 static NOINLINE const char *get_homedir_or_NULL(void)
 {
         const char *home;
@@ -275,6 +267,16 @@ static NOINLINE const char *get_homedir_or_NULL(void)
 }
 #endif
 
+#if ENABLE_FEATURE_EDITING_FANCY_PROMPT
+static const char *get_username_str(void)
+{
+        if (!got_user_strings)
+                get_user_strings();
+        return user_buf ? user_buf : "";
+        /* btw, bash uses "I have no name!" string if uid has no entry */
+}
+#endif
+
 #if ENABLE_UNICODE_SUPPORT
 static size_t load_string(const char *src)
 {
@@ -2151,13 +2153,13 @@ static void parse_and_put_prompt(const char *prmt_ptr)
                                 case 'W': /* basename of cur dir */
                                         if (!cwd_buf) {
                                                 const char *home;
-#if ENABLE_SHELL_ASH
+# if EDITING_HAS_sh_get_var
                                                 cwd_buf = state->sh_get_var
                                                         ? xstrdup(state->sh_get_var("PWD"))
                                                         : xrealloc_getcwd_or_warn(NULL);
-#else
+# else
                                                 cwd_buf = xrealloc_getcwd_or_warn(NULL);
-#endif
+# endif
                                                 if (!cwd_buf)
                                                         cwd_buf = (char *)bb_msg_unknown;
                                                 else if ((home = get_homedir_or_NULL()) != NULL && home[0]) {
diff --git a/libbb/loop.c b/libbb/loop.c
index cb8fa2442..a0c5d0259 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -71,7 +71,7 @@ int FAST_FUNC del_loop(const char *device)
 
         fd = open(device, O_RDONLY);
         if (fd < 0)
-                return 1;
+                return fd; /* -1 */
         rc = ioctl(fd, LOOP_CLR_FD, 0);
         close(fd);
 
@@ -96,6 +96,97 @@ int FAST_FUNC get_free_loop(void)
         return loopdevno; /* can be -1 if error */
 }
 
+static int get_next_free_loop(char *dev, int id)
+{
+        int loopdevno;
+
+        loopdevno = get_free_loop();
+        if (loopdevno != -1) {
+                /* loopdevno is -2 (use id) or >= 0 (use id = loopdevno): */
+                if (loopdevno >= 0)
+                        id = loopdevno;
+                sprintf(dev, LOOP_FORMAT, id);
+        }
+        return loopdevno;
+}
+
+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE
+# define LOOP_CONFIGURE 0x4C0A
+struct bb_loop_config {
+        uint32_t fd;
+        uint32_t block_size;
+        struct loop_info64 info;
+        uint64_t __reserved[8];
+};
+#endif
+
+static int set_loopdev_params(int lfd,
+                int ffd, const char *file,
+                unsigned long long offset,
+                unsigned long long sizelimit,
+                unsigned flags)
+{
+        int rc;
+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE
+        struct bb_loop_config lconfig;
+# define loopinfo lconfig.info
+#else
+        bb_loop_info loopinfo;
+#endif
+
+        rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
+
+        /* If device is free, try to claim it */
+        if (rc && errno == ENXIO) {
+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE
+                memset(&lconfig, 0, sizeof(lconfig));
+#else
+                memset(&loopinfo, 0, sizeof(loopinfo));
+#endif
+                safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
+                loopinfo.lo_offset = offset;
+                loopinfo.lo_sizelimit = sizelimit;
+                /*
+                 * LO_FLAGS_READ_ONLY is not set because RO is controlled
+                 * by open type of the lfd.
+                 */
+                loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
+
+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE
+                lconfig.fd = ffd;
+                rc = ioctl(lfd, LOOP_CONFIGURE, &lconfig);
+                if (rc == 0)
+                        return rc; /* SUCCESS! */
+# if ENABLE_TRY_LOOP_CONFIGURE
+                if (errno != EINVAL)
+                        return rc; /* error other than old kernel */
+                /* Old kernel, fall through into old way to do it: */
+# endif
+#endif
+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_NO_LOOP_CONFIGURE
+                /* Associate free loop device with file */
+                rc = ioctl(lfd, LOOP_SET_FD, ffd);
+                if (rc != 0) {
+                        /* Ouch... race: the device already has a fd */
+                        return rc;
+                }
+                rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
+                if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
+                        /* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
+                        /* (this code path is not tested) */
+                        loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
+                        rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
+                }
+                if (rc == 0)
+                        return rc; /* SUCCESS! */
+                /* failure, undo LOOP_SET_FD */
+                ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+#endif
+        }
+        return -1;
+#undef loopinfo
+}
+
 /* Returns opened fd to the loop device, <0 on error.
  * *device is loop device to use, or if *device==NULL finds a loop device to
  * mount it on and sets *device to a strdup of that loop device name.
@@ -105,7 +196,6 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 {
         char dev[LOOP_NAMESIZE];
         char *try;
-        bb_loop_info loopinfo;
         struct stat statbuf;
         int i, lfd, ffd, mode, rc;
 
@@ -123,30 +213,27 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
 
         try = *device;
         if (!try) {
- get_free_loopN:
-                i = get_free_loop();
-                if (i == -1) {
-                        close(ffd);
-                        return -1; /* no free loop devices */
-                }
-                if (i >= 0) {
-                        try = xasprintf(LOOP_FORMAT, i);
-                        goto open_lfd;
-                }
-                /* i == -2: no /dev/loop-control. Do an old-style search for a free device */
                 try = dev;
         }
 
         /* Find a loop device */
         /* 0xfffff is a max possible minor number in Linux circa 2010 */
         for (i = 0; i <= 0xfffff; i++) {
-                sprintf(dev, LOOP_FORMAT, i);
+                if (!*device) {
+                        rc = get_next_free_loop(dev, i);
+                        if (rc == -1)
+                                break; /* no free loop devices (or other error in LOOP_CTL_GET_FREE) */
+                        if (rc >= 0)
+                                /* /dev/loop-control gave us the next free /dev/loopN */
+                                goto open_lfd;
+                        /* else: sequential /dev/loopN, needs to be tested/maybe_created */
+                }
 
                 IF_FEATURE_MOUNT_LOOP_CREATE(errno = 0;)
                 if (stat(try, &statbuf) != 0 || !S_ISBLK(statbuf.st_mode)) {
                         if (ENABLE_FEATURE_MOUNT_LOOP_CREATE
                          && errno == ENOENT
-                         && try == dev
+                         && (!*device)
                         ) {
                                 /* Node doesn't exist, try to create it */
                                 if (mknod(dev, S_IFBLK|0644, makedev(7, i)) == 0)
@@ -172,55 +259,19 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
                         goto try_next_loopN;
                 }
 
-                rc = ioctl(lfd, BB_LOOP_GET_STATUS, &loopinfo);
-
-                /* If device is free, try to claim it */
-                if (rc && errno == ENXIO) {
-                        /* Associate free loop device with file */
-                        if (ioctl(lfd, LOOP_SET_FD, ffd)) {
-                                /* Ouch. Are we racing with other mount? */
-                                if (!*device   /* yes */
-                                 && try != dev /* tried a _kernel-offered_ loopN? */
-                                ) {
-                                        free(try);
-                                        close(lfd);
-//TODO: add "if (--failcount != 0) ..."?
-                                        goto get_free_loopN;
-                                }
-                                goto close_and_try_next_loopN;
-                        }
-                        memset(&loopinfo, 0, sizeof(loopinfo));
-                        safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
-                        loopinfo.lo_offset = offset;
-                        loopinfo.lo_sizelimit = sizelimit;
-                        /*
-                         * Used by mount to set LO_FLAGS_AUTOCLEAR.
-                         * LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
-                         * Note that closing LO_FLAGS_AUTOCLEARed lfd before mount
-                         * is wrong (would free the loop device!)
+                rc = set_loopdev_params(lfd, ffd, file, offset, sizelimit, flags);
+                if (rc == 0) {
+                        /* SUCCESS! */
+                        if (!*device)
+                                *device = xstrdup(dev);
+                        /* Note: mount asks for LO_FLAGS_AUTOCLEAR loopdev.
+                         * Closing LO_FLAGS_AUTOCLEARed lfd before mount
+                         * is wrong (would free the loop device!),
+                         * this is why we return without closing it.
                          */
-                        loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
-                        rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
-                        if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
-                                /* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
-                                /* (this code path is not tested) */
-                                loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
-                                rc = ioctl(lfd, BB_LOOP_SET_STATUS, &loopinfo);
-                        }
-                        if (rc == 0) {
-                                /* SUCCESS! */
-                                if (try != dev) /* tried a kernel-offered free loopN? */
-                                        *device = try; /* malloced */
-                                if (!*device)   /* was looping in search of free "/dev/loopN"? */
-                                        *device = xstrdup(dev);
-                                rc = lfd; /* return this */
-                                break;
-                        }
-                        /* failure, undo LOOP_SET_FD */
-                        ioctl(lfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary
+                        rc = lfd; /* return this */
+                        break;
                 }
-                /* else: device is not free (rc == 0) or error other than ENXIO */
- close_and_try_next_loopN:
                 close(lfd);
  try_next_loopN:
                 rc = -1;