Replaced emubd with rambd and filebd

The idea behind emubd (file per block), was neat, but doesn't add much
value over a block device that just operates on a single linear file
(other than adding a significant amount of overhead). Initially it
helped with debugging, but when the metadata format became more complex
in v2, most debugging ends up going through the debug.py script anyways.

Aside from being simpler, moving to filebd means it is also possible to
mount disk images directly.

Also introduced rambd, which keeps the disk contents in RAM. This is
very useful for testing where it increases the speed _significantly_.
- test_dirs w/ filebd - 0m7.170s
- test_dirs w/ rambd  - 0m0.966s

These follow the emubd model of using the lfs_config for geometry. I'm
not convinced this is the best approach, but it gets the job done.

I've also added lfs_ramdb_createcfg to add additional config similar to
lfs_file_opencfg. This is useful for specifying erase_value, which tells
the block device to simulate erases similar to flash devices. Note that
the default (-1) meets the minimum block device requirements and is the
most performant.

filebd/lfs_filebd.c

@@ -0,0 +1,198 @@
+/*
+ * Block device emulated in a file
+ *
+ * Copyright (c) 2017, Arm Limited. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include "filebd/lfs_filebd.h"
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+int lfs_filebd_createcfg(const struct lfs_config *cfg, const char *path,
+        const struct lfs_filebd_config *filecfg) {
+    LFS_TRACE("lfs_filebd_createcfg(%p {.context=%p, "
+                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
+                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
+                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
+                "\"%s\", "
+                "%p {.erase_value=%"PRId32"})",
+            (void*)cfg, cfg->context,
+            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
+            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
+            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
+            path, (void*)filecfg, filecfg->erase_value);
+    lfs_filebd_t *bd = cfg->context;
+    bd->cfg = filecfg;
+
+    // open file
+    bd->fd = open(path, O_RDWR | O_CREAT, 0666);
+    if (bd->fd < 0) {
+        int err = -errno;
+        LFS_TRACE("lfs_filebd_createcfg -> %d", err);
+        return err;
+    }
+
+    LFS_TRACE("lfs_filebd_createcfg -> %d", 0);
+    return 0;
+}
+
+int lfs_filebd_create(const struct lfs_config *cfg, const char *path) {
+    LFS_TRACE("lfs_filebd_create(%p {.context=%p, "
+                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
+                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
+                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
+                "\"%s\")",
+            (void*)cfg, cfg->context,
+            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
+            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
+            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
+            path);
+    static const struct lfs_filebd_config defaults = {.erase_value=-1};
+    int err = lfs_filebd_createcfg(cfg, path, &defaults);
+    LFS_TRACE("lfs_filebd_create -> %d", err);
+    return err;
+}
+
+void lfs_filebd_destroy(const struct lfs_config *cfg) {
+    LFS_TRACE("lfs_filebd_destroy(%p)", (void*)cfg);
+    lfs_filebd_t *bd = cfg->context;
+    close(bd->fd);
+    LFS_TRACE("lfs_filebd_destroy -> %s", "void");
+}
+
+int lfs_filebd_read(const struct lfs_config *cfg, lfs_block_t block,
+        lfs_off_t off, void *buffer, lfs_size_t size) {
+    LFS_TRACE("lfs_filebd_read(%p, 0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
+            (void*)cfg, block, off, buffer, size);
+    lfs_filebd_t *bd = cfg->context;
+
+    // check if read is valid
+    LFS_ASSERT(off  % cfg->read_size == 0);
+    LFS_ASSERT(size % cfg->read_size == 0);
+    LFS_ASSERT(block < cfg->block_count);
+
+    // zero for reproducability (in case file is truncated)
+    if (bd->cfg->erase_value != -1) {
+        memset(buffer, bd->cfg->erase_value, size);
+    }
+
+    // read
+    off_t res1 = lseek(bd->fd,
+            (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+    if (res1 < 0) {
+        int err = -errno;
+        LFS_TRACE("lfs_filebd_read -> %d", err);
+        return err;
+    }
+
+    ssize_t res2 = read(bd->fd, buffer, size);
+    if (res2 < 0) {
+        int err = -errno;
+        LFS_TRACE("lfs_filebd_read -> %d", err);
+        return err;
+    }
+
+    LFS_TRACE("lfs_filebd_read -> %d", 0);
+    return 0;
+}
+
+int lfs_filebd_prog(const struct lfs_config *cfg, lfs_block_t block,
+        lfs_off_t off, const void *buffer, lfs_size_t size) {
+    LFS_TRACE("lfs_filebd_prog(%p, 0x%"PRIx32", %"PRIu32", %p, %"PRIu32")",
+            (void*)cfg, block, off, buffer, size);
+    lfs_filebd_t *bd = cfg->context;
+
+    // check if write is valid
+    LFS_ASSERT(off  % cfg->prog_size == 0);
+    LFS_ASSERT(size % cfg->prog_size == 0);
+    LFS_ASSERT(block < cfg->block_count);
+
+    // check that data was erased? only needed for testing
+    if (bd->cfg->erase_value != -1) {
+        off_t res1 = lseek(bd->fd,
+                (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+        if (res1 < 0) {
+            int err = -errno;
+            LFS_TRACE("lfs_filebd_prog -> %d", err);
+            return err;
+        }
+
+        for (lfs_off_t i = 0; i < size; i++) {
+            uint8_t c;
+            ssize_t res2 = read(bd->fd, &c, 1);
+            if (res2 < 0) {
+                int err = -errno;
+                LFS_TRACE("lfs_filebd_prog -> %d", err);
+                return err;
+            }
+
+            LFS_ASSERT(c == bd->cfg->erase_value);
+        }
+    }
+
+    // program data
+    off_t res1 = lseek(bd->fd,
+            (off_t)block*cfg->block_size + (off_t)off, SEEK_SET);
+    if (res1 < 0) {
+        int err = -errno;
+        LFS_TRACE("lfs_filebd_prog -> %d", err);
+        return err;
+    }
+
+    ssize_t res2 = write(bd->fd, buffer, size);
+    if (res2 < 0) {
+        int err = -errno;
+        LFS_TRACE("lfs_filebd_prog -> %d", err);
+        return err;
+    }
+
+    LFS_TRACE("lfs_filebd_prog -> %d", 0);
+    return 0;
+}
+
+int lfs_filebd_erase(const struct lfs_config *cfg, lfs_block_t block) {
+    LFS_TRACE("lfs_filebd_erase(%p, 0x%"PRIx32")", (void*)cfg, block);
+    lfs_filebd_t *bd = cfg->context;
+
+    // check if erase is valid
+    LFS_ASSERT(block < cfg->block_count);
+
+    // erase, only needed for testing
+    if (bd->cfg->erase_value != -1) {
+        off_t res1 = lseek(bd->fd, (off_t)block*cfg->block_size, SEEK_SET);
+        if (res1 < 0) {
+            int err = -errno;
+            LFS_TRACE("lfs_filebd_erase -> %d", err);
+            return err;
+        }
+
+        for (lfs_off_t i = 0; i < cfg->block_size; i++) {
+            ssize_t res2 = write(bd->fd, &(uint8_t){bd->cfg->erase_value}, 1);
+            if (res2 < 0) {
+                int err = -errno;
+                LFS_TRACE("lfs_filebd_erase -> %d", err);
+                return err;
+            }
+        }
+    }
+
+    LFS_TRACE("lfs_filebd_erase -> %d", 0);
+    return 0;
+}
+
+int lfs_filebd_sync(const struct lfs_config *cfg) {
+    LFS_TRACE("lfs_filebd_sync(%p)", (void*)cfg);
+    // file sync
+    lfs_filebd_t *bd = cfg->context;
+    int err = fsync(bd->fd);
+    if (err) {
+        err = -errno;
+        LFS_TRACE("lfs_filebd_sync -> %d", 0);
+        return err;
+    }
+
+    LFS_TRACE("lfs_filebd_sync -> %d", 0);
+    return 0;
+}