Added block driver client and server

errors/errno.fugu

@@ -1154,6 +1154,7 @@ errors fat FAT_ERR_ {
     failure BLOCK_BOUNDS        "The block number is out of bounds",
     failure CREATE_ROOT         "Tried to create root directory",
     failure BAD_FILENAME        "Filename is not allowed",
+    failure TOO_MANY_HANDLES    "Currently the FAT32 library allows at most FAT32_MAX_OPEN_HANDLERS handlers per dir/file",
 };
 
 // errors generated by VFS's fs cache library
@@ -1433,3 +1434,9 @@ errors sdhc SDHCD_ERR_ {
     failure BULK_FRAME_SET             "Bulk frame already set",
     failure BULK_FRAME_NOT_SET         "Bulk frame not set",
 };
+
+// errors for block driver server
+errors block BLOCK_ERR_ {
+    failure OVERFLOW_BLOCK             "Client tried to operate over block bounds",
+    failure WRITE_BOOTSECTOR           "Client tried to overwrite the boot sector",
+};

hake/menu.lst.armv8_imx8x

@@ -12,3 +12,4 @@ module /armv8/sbin/mallocator
 module /armv8/sbin/stackoverflow
 module /armv8/sbin/echoserver
 module /armv8/sbin/shelly
+module /armv8/sbin/block_driver_server

include/aos/ump_binding.h

@@ -8,6 +8,7 @@
 enum ump_server_id {
     UMP_SERVER_ECHO,
     UMP_SERVER_NET,
+    UMP_SERVER_BLOCK_DRIVER,
     UMP_SERVER_COUNT // How many servers exist
 };
 

include/drivers/block_driver.h

@@ -0,0 +1,39 @@
+#ifndef _INIT_BLOCK_DRIVER_H_
+#define _INIT_BLOCK_DRIVER_H_
+
+#include <aos/aos.h>
+
+enum block_driver_action {
+    BLOCK_DRIVER_ACTION_READ,
+    BLOCK_DRIVER_ACTION_WRITE,
+    BLOCK_DRIVER_ACTION_LOCK,
+    BLOCK_DRIVER_ACTION_UNLOCK,
+    BLOCK_DRIVER_ACTION_REGISTER_HANDLE,
+    BLOCK_DRIVER_ACTION_UNREGISTER_HANDLE,
+    BLOCK_DRIVER_ACTION_COUNT_HANDLES
+};
+
+struct block_driver_request {
+    enum block_driver_action action;
+    size_t block_number;
+    size_t offset;
+    size_t bytes;
+    uint64_t directory_entry_id;
+};
+
+struct block_driver_result {
+    errval_t err;
+};
+
+errval_t block_driver_init(void);
+
+errval_t block_driver_read_object(uint32_t sector_number, size_t offset, size_t size, void *dst);
+errval_t block_driver_write_object(uint32_t sector_number, size_t offset, size_t size, const void *src);
+errval_t block_driver_lock(void);
+errval_t block_driver_unlock(void);
+
+errval_t block_driver_register_handle(uint64_t directory_entry_id);
+errval_t block_driver_unregister_handle(uint64_t directory_entry_id);
+errval_t block_driver_count_handles(uint64_t directory_entry_id, size_t *count);
+
+#endif /* _INIT_BLOCK_DRIVER_H_ */

lib/block_driver/Hakefile

@@ -0,0 +1,20 @@
+--------------------------------------------------------------------------
+-- Copyright (c) 2007-2012, ETH Zurich.
+-- All rights reserved.
+--
+-- This file is distributed under the terms in the attached LICENSE file.
+-- If you do not find this file, copies can be found by writing to:
+-- ETH Zurich D-INFK, Haldeneggsteig 4, CH-8092 Zurich. Attn: Systems Group.
+--
+-- Hakefile for lib/vfs
+--
+--------------------------------------------------------------------------
+
+[
+  build library {
+    target = "block_driver",
+    cFiles = [
+        "block_driver.c"
+    ]
+  }
+]

lib/block_driver/block_driver.c

@@ -0,0 +1,167 @@
+#include <aos/ump_chan.h>
+#include <aos/aos_rpc.h>
+#include <aos/deferred.h>
+
+#include <drivers/block_driver.h>
+
+struct block_driver_state {
+    struct ump_send_chan *send_chan;
+    struct ump_recv_chan *recv_chan;
+
+    bool request_ongoing;
+    struct block_driver_request *current_request;
+    void *read_buf;
+    errval_t result;
+};
+
+static struct block_driver_state state = {
+    .recv_chan = NULL,
+    .send_chan = NULL,
+};
+
+// use a waitset to make the calls blocking
+struct waitset ws;
+
+errval_t block_driver_init(void) {
+    errval_t err;
+
+    waitset_init(&ws);
+
+    // connect to the block driver
+    struct capref cap;
+    struct aos_rpc *rpc = aos_rpc_get_init_channel();
+    // retry several times, waiting inbetween in case the server is still starting up
+    for (int attempts = 0; attempts < 50; attempts++) {
+        err = aos_rpc_ump_connect(rpc, UMP_SERVER_BLOCK_DRIVER, &cap);
+        if (err_no(err) != LIB_ERR_UMP_NOT_REGISTERED) break;
+        barrelfish_usleep(100000);
+    }
+    if (err_is_fail(err)) return err;
+
+    // Create the two uni-directional channels
+    struct ump_send_chan *send_chan;
+    struct ump_recv_chan *recv_chan;
+    err = ump_chan_init(UMP_ROLE_CLIENT, &send_chan, &recv_chan, sizeof(struct block_driver_result), cap, &ws);
+    if (err_is_fail(err)) return err;
+
+    state.recv_chan = recv_chan;
+    state.send_chan = send_chan;
+    state.request_ongoing = false;
+    state.current_request = NULL;
+    state.read_buf = NULL;
+    state.result = SYS_ERR_OK;
+
+    return SYS_ERR_OK;
+}
+
+static void handle_payload(void *arg, size_t payload_size, void *payload) {
+    state.request_ongoing = false;
+}
+
+static void handle_response(void *arg, size_t header_size, void *header, size_t payload_size) {
+    struct block_driver_result *result = header;
+
+    state.result = result->err;
+
+    if (state.current_request->action == BLOCK_DRIVER_ACTION_READ && err_is_ok(result->err)) {
+        if (payload_size != state.current_request->bytes) {
+            USER_PANIC("We should always receive as much as requested or an error");
+        }
+        // receive the payload in the buffer passed to the blocking function
+        ump_recv_payload(state.recv_chan, state.read_buf, handle_payload, NULL);
+        return;
+    } else if (state.current_request->action == BLOCK_DRIVER_ACTION_COUNT_HANDLES && err_is_ok(result->err)) {
+        if (payload_size != sizeof(size_t)) {
+            USER_PANIC("We should always receive a size_t result for this request or an error");
+        }
+        // receive the payload in the buffer passed to the blocking function
+        ump_recv_payload(state.recv_chan, state.read_buf, handle_payload, NULL);
+        return;
+    }
+
+
+    ump_recv_payload(state.recv_chan, NULL, handle_payload, NULL);
+}
+
+static void handle_send_completed(void *arg, struct ump_send_queue_entry *entry) {
+    free((void *)entry->header);
+    free(entry);
+}
+
+static errval_t send_blocking_request(enum block_driver_action action, uint64_t directory_entry_id, uint32_t sector_number, size_t offset, size_t size, size_t payload_size, const void *payload) {
+    assert(state.recv_chan != NULL);
+    assert(state.send_chan != NULL);
+    assert(!state.request_ongoing);
+
+    errval_t err;
+
+    state.request_ongoing = true;
+    
+    // send the read request
+    struct block_driver_request *request = malloc(sizeof(struct block_driver_request));
+    if (request == NULL) return LIB_ERR_MALLOC_FAIL;
+    struct ump_send_queue_entry *entry = malloc(sizeof(struct ump_send_queue_entry));
+    if (entry == NULL) return LIB_ERR_MALLOC_FAIL;
+
+    request->action = action;
+    request->block_number = sector_number;
+    request->bytes = size;
+    request->offset = offset;
+    request->directory_entry_id = directory_entry_id;
+    state.current_request = request;
+    assert(state.send_chan->send_queue_head == NULL);
+    ump_send(
+        state.send_chan,
+        entry,
+        sizeof(struct block_driver_request),
+        request,
+        payload_size,
+        payload,
+        handle_send_completed,
+        NULL
+    );
+
+    // register response handler
+    ump_recv_header(state.recv_chan, handle_response, NULL);
+
+    // wait for the response
+    while (state.request_ongoing) {
+        err = event_dispatch(&ws);
+        if (err_is_fail(err)) {
+            DEBUG_ERR(err, "in event_dispatch");
+            abort();
+        }
+    }
+
+    return state.result;
+}
+
+errval_t block_driver_read_object(uint32_t sector_number, size_t offset, size_t size, void *dst) {
+    state.read_buf = dst;
+    return send_blocking_request(BLOCK_DRIVER_ACTION_READ, 0, sector_number, offset, size, 0, NULL);
+}
+
+errval_t block_driver_write_object(uint32_t sector_number, size_t offset, size_t size, const void *src) {
+    return send_blocking_request(BLOCK_DRIVER_ACTION_WRITE, 0, sector_number, offset, size, size, src);
+}
+
+errval_t block_driver_lock(void) {
+    return send_blocking_request(BLOCK_DRIVER_ACTION_LOCK, 0, 0, 0, 0, 0, NULL);
+}
+
+errval_t block_driver_unlock(void) {
+    return send_blocking_request(BLOCK_DRIVER_ACTION_UNLOCK, 0, 0, 0, 0, 0, NULL);
+}
+
+errval_t block_driver_register_handle(uint64_t directory_entry_id) {
+    return send_blocking_request(BLOCK_DRIVER_ACTION_REGISTER_HANDLE, directory_entry_id, 0, 0, 0, 0, NULL);
+}
+
+errval_t block_driver_unregister_handle(uint64_t directory_entry_id) {
+    return send_blocking_request(BLOCK_DRIVER_ACTION_UNREGISTER_HANDLE, directory_entry_id, 0, 0, 0, 0, NULL);
+}
+
+errval_t block_driver_count_handles(uint64_t directory_entry_id, size_t *count) {
+    state.read_buf = count;
+    return send_blocking_request(BLOCK_DRIVER_ACTION_COUNT_HANDLES, directory_entry_id, 0, 0, 0, 0, NULL);
+}

lib/spawn/spawn.c

@@ -509,6 +509,10 @@ errval_t spawn_load_argv(int argc, char *argv[], struct spawninfo *si,
         arg0_base = IMX8X_ENET_BASE;
         arg0_size = IMX8X_ENET_SIZE;
     }
+    if (strcmp(argv[0], "block_driver_server") == 0) {
+        arg0_base = IMX8X_SDHC2_BASE;
+        arg0_size = IMX8X_SDHC_SIZE;
+    }
 
     si->cspace_l2_cnode_argcn = NULL_CNODE;
     if (arg0_base != 0) {

performance/performance_evaluation.py

@@ -67,12 +67,20 @@ def main():
 
     dataset = {}
 
-    dataset["performance"] = build_dataseries(measurements, "aos_performance:start", "aos_performance:done")
+    # dataset["performance"] = build_dataseries(measurements, "aos_performance:start", "aos_performance:done")
 
-    dataset["client_to_server"] = build_dataseries(measurements, "aos_urpc_nop:start", "aos_urpc_server:start")
-    dataset["server_schedule_task"] = build_dataseries(measurements, "aos_urpc_server:start", "aos_urpc_server:triggered_closure")
-    dataset["server_completed_task"] = build_dataseries(measurements, "aos_urpc_server:triggered_closure", "aos_urpc_server:done")
-    dataset["server_to_client"] = build_dataseries(measurements, "aos_urpc_server:done", "aos_urpc_nop:done")
+    # URPC
+    # dataset["client_to_server"] = build_dataseries(measurements, "aos_urpc_nop:start", "aos_urpc_server:start")
+    # dataset["server_schedule_task"] = build_dataseries(measurements, "aos_urpc_server:start", "aos_urpc_server:triggered_closure")
+    # dataset["server_completed_task"] = build_dataseries(measurements, "aos_urpc_server:triggered_closure", "aos_urpc_server:done")
+    # dataset["server_to_client"] = build_dataseries(measurements, "aos_urpc_server:done", "aos_urpc_nop:done")
+
+    # block driver
+    dataset["block_driver_read_device"] = build_dataseries(measurements, "block_driver_read_object:start", "block_driver_read_object:memcpy")
+    dataset["block_driver_read_memcpy"] = build_dataseries(measurements, "block_driver_read_object:memcpy", "block_driver_read_object:done")
+    dataset["block_driver_write_read"] = build_dataseries(measurements, "block_driver_write_object:start", "block_driver_write_object:read")
+    dataset["block_driver_write_memcpy"] = build_dataseries(measurements, "block_driver_write_object:read", "block_driver_write_object:memcpy")
+    dataset["block_driver_write_device"] = build_dataseries(measurements, "block_driver_write_object:memcpy", "block_driver_write_object:done")
 
     # calculate stats for each data series
     metrics = {}

platforms/Hakefile

@@ -12,7 +12,7 @@
 
 let
     -- Default list of modules to build/install
-    modules_common = [ "/sbin/" ++ f | f <- [ "init", "hello", "mallocator", "stackoverflow", "echoserver", "enet", "shelly"
+    modules_common = [ "/sbin/" ++ f | f <- [ "init", "hello", "mallocator", "stackoverflow", "echoserver", "enet", "shelly", "block_driver_server"
       ] ]
   in
   [

usr/drivers/block_driver_server/Hakefile

@@ -0,0 +1,30 @@
+--------------------------------------------------------------------------
+-- Copyright (c) 2020, ETH Zurich.
+-- All rights reserved.
+--
+-- This file is distributed under the terms in the attached LICENSE file.
+-- If you do not find this file, copies can be found by writing to:
+-- ETH Zurich D-INFK, CAB F.78, Universitaetstr 6, CH-8092 Zurich.
+--
+-- Hakefile for sdhc 
+--
+--------------------------------------------------------------------------
+--------------------------------------------------------------------------
+-- Copyright (c) 2007-2010, ETH Zurich.
+-- All rights reserved.
+--
+-- This file is distributed under the terms in the attached LICENSE file.
+-- If you do not find this file, copies can be found by writing to:
+-- ETH Zurich D-INFK, Haldeneggsteig 4, CH-8092 Zurich. Attn: Systems Group.
+--
+-- Hakefile for /usr/init
+--
+--------------------------------------------------------------------------
+
+[ build application
+  {
+    target = "block_driver_server",
+    cFiles = [ "main.c" ],
+    addLibraries = [ "sdhc" ]
+  }
+]

usr/drivers/block_driver_server/main.c

@@ -0,0 +1,494 @@
+#include <aos/aos.h>
+#include <aos/paging.h>
+#include <aos/ump_binding.h>
+#include <aos/ump_chan.h>
+#include <drivers/block_driver.h>
+#include <aos/cache.h>
+
+#include <maps/imx8x_map.h>
+#include <drivers/sdhc.h>
+
+// #define BLOCK_DRIVER_PERFORMANCE
+#ifdef BLOCK_DRIVER_PERFORMANCE
+#include <aos/performance.h>
+struct performance_context pcontext;
+#endif
+
+struct block_driver_state {
+    struct ump_send_chan *send_chan;
+    struct ump_recv_chan *recv_chan;
+    struct block_driver_request *current_request;
+    struct block_driver_state *next;
+};
+
+static struct sdhc_s *sdhc;
+
+static void *dma_buffer;
+static genpaddr_t dma_buffer_phys;
+
+static bool locked = false;
+static struct block_driver_state *lock_queue_head = NULL;
+static struct block_driver_state *lock_queue_tail = NULL;
+
+// list of open file handles because we have to synchronize on open dirs/files vs deletion
+struct handle {
+    uint64_t directory_entry_id;
+    size_t count;
+    struct handle *next;
+    struct handle *prev;
+};
+struct handle *handle_list_head = NULL;
+struct handle *handle_list_tail = NULL;
+
+#define BLOCK_DRIVER_CACHE
+#ifdef BLOCK_DRIVER_CACHE
+uint32_t current_block_in_buffer = UINT32_MAX;
+#endif
+
+static errval_t read_buffer(int block_number) {
+    assert(block_number != UINT32_MAX);
+
+    errval_t err;
+
+    // debug_printf("[block_driver_server] read block %d\n", block_number);
+
+    #ifdef BLOCK_DRIVER_CACHE
+    // very primitive cache for the last read block
+    if(current_block_in_buffer == block_number) {
+        return SYS_ERR_OK;
+    }
+    #endif
+
+    err = sdhc_read_block(sdhc, block_number, (lpaddr_t)dma_buffer_phys);
+    if(err_is_fail(err)) {
+        #ifdef BLOCK_DRIVER_CACHE
+        // maybe there was a partial modification so invalidate the cache
+        current_block_in_buffer = UINT32_MAX;
+        #endif
+        return err;
+    }
+    #ifdef BLOCK_DRIVER_CACHE
+    current_block_in_buffer = block_number;
+    #endif
+
+    __asm volatile (
+        "dmb sy\n"
+    );
+    cpu_dcache_wbinv_range((genvaddr_t)dma_buffer, SDHC_BLOCK_SIZE);
+
+    return SYS_ERR_OK;
+}
+
+static errval_t write_buffer(int block_number) {
+    assert(block_number != UINT32_MAX);
+
+    errval_t err;
+
+    // debug_printf("[block_driver_server] write block %d\n", block_number);
+
+    __asm volatile (
+        "dmb sy\n"
+    );
+    cpu_dcache_wbinv_range((genvaddr_t)dma_buffer, SDHC_BLOCK_SIZE);
+
+    err = sdhc_write_block(sdhc, block_number, (lpaddr_t)dma_buffer_phys);
+    if(err_is_fail(err)) return err;
+
+    return SYS_ERR_OK;
+}
+
+static struct handle *search_element(uint64_t directory_entry_id) {
+    struct handle *cur_handle = handle_list_head;
+    while(cur_handle != NULL && cur_handle->directory_entry_id != directory_entry_id) {
+        cur_handle = cur_handle->next;
+    }
+    return cur_handle;
+}
+
+static void insert_element(uint64_t directory_entry_id) {
+    struct handle *element_handle = calloc(1, sizeof(struct handle));
+    if (element_handle == NULL) USER_PANIC("Ran out of memory");
+
+    element_handle->count = 1;
+    element_handle->directory_entry_id = directory_entry_id;
+
+    element_handle->prev = handle_list_tail;
+    element_handle->next = NULL;
+    if(handle_list_head == NULL) {
+        handle_list_head = element_handle;
+    } else {
+        handle_list_tail->next = element_handle;
+    }
+    handle_list_tail = element_handle;
+}
+
+static void remove_element(struct handle *element_handle) {
+    if (element_handle->prev == NULL) {
+        handle_list_head = element_handle->next;
+    } else {
+        element_handle->prev->next = element_handle->next;
+    }
+    if (element_handle->next == NULL) {
+        handle_list_tail = element_handle->prev;
+    } else {
+        element_handle->next->prev = element_handle->prev;
+    }
+}
+
+__attribute__((__unused__))
+static void print_handles(void) {
+    struct handle *element_handle = handle_list_head;
+    debug_printf("Handle List\n");
+    while (element_handle != NULL) {
+        debug_printf("Handle %lu: %lu\n", element_handle->directory_entry_id, element_handle->count);
+        element_handle = element_handle->next;
+    }
+}
+
+static errval_t register_handle(uint64_t directory_entry_id) {
+    // debug_printf("Register %lu\n", directory_entry_id);
+    struct handle *element_handle = search_element(directory_entry_id);
+    if (element_handle == NULL) {
+        insert_element(directory_entry_id);
+    } else if(element_handle->count == SIZE_MAX) {
+        return FAT_ERR_TOO_MANY_HANDLES;
+    }else {
+        ++element_handle->count;
+    }
+    // print_handles();
+
+    return SYS_ERR_OK;
+}
+
+static errval_t unregister_handle(uint64_t directory_entry_id) {
+    // debug_printf("Unegister %lu\n", directory_entry_id);
+    struct handle *element_handle = search_element(directory_entry_id);
+    if (element_handle == NULL) {
+        return ERR_INVALID_ARGS;
+    } else if (element_handle->count == 1) {
+        remove_element(element_handle);
+    } else {
+        --element_handle->count;
+    }
+    // print_handles();
+    return SYS_ERR_OK;
+}
+
+static size_t count_handles(uint64_t directory_entry_id) {
+    struct handle *element_handle = search_element(directory_entry_id);
+    if (element_handle == NULL) {
+        return 0;
+    } else {
+        return element_handle->count;
+    }
+}
+
+static errval_t read_object(uint32_t block_number, size_t offset, size_t size, void *dst) {
+    errval_t err;
+
+    // printf("[block_driver_server] reading %lu bytes from %lu@%u to %p\n", size, offset, block_number, dst);
+
+    // sector bounds check
+    if (offset + size > SDHC_BLOCK_SIZE) {
+        return BLOCK_ERR_OVERFLOW_BLOCK;
+    }
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_init(&pcontext, "block_driver_read_object");
+    perf_add_now(&pcontext, "start");
+    #endif
+
+    err = read_buffer(block_number);
+    if (err_is_fail(err)) return err;
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_add_now(&pcontext, "memcpy");
+    #endif
+
+    memcpy(dst, dma_buffer + offset, size);
+
+    // debug_printf("Read start: '%.5s'\n", dst);
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_add_now(&pcontext, "done");
+    perf_print(&pcontext);
+    #endif
+
+    return SYS_ERR_OK;
+}
+
+static errval_t write_object(uint32_t block_number, size_t offset, size_t size, void *src) {
+    errval_t err;
+
+    // printf("[block_driver_server] writing %lu bytes from %p to %lu@%u\n", size, src, offset, block_number);
+
+    // sector bounds check
+    if (offset + size > SDHC_BLOCK_SIZE) {
+        return BLOCK_ERR_OVERFLOW_BLOCK;
+    }
+
+    // we never modify the bpb and boot sector
+    if (block_number == 0) {
+        return BLOCK_ERR_WRITE_BOOTSECTOR;
+    }
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_init(&pcontext, "block_driver_write_object");
+    perf_add_now(&pcontext, "start");
+    #endif
+
+    // if we are not writing the full block then we need to copy the current block
+    if (size < SDHC_BLOCK_SIZE) {
+        err = read_buffer(block_number);
+        if (err_is_fail(err)) return err;
+    }
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_add_now(&pcontext, "read");
+    #endif
+
+    // debug_printf("Write start: '%.5s'\n", src);
+    memcpy(dma_buffer + offset, src, size);
+    
+    #ifdef BLOCK_DRIVER_CACHE
+    // update the cache metadata
+    current_block_in_buffer = block_number;
+    #endif
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_add_now(&pcontext, "memcpy");
+    #endif
+
+    err = write_buffer(block_number);
+    if (err_is_fail(err)) return err;
+
+    #ifdef BLOCK_DRIVER_PERFORMANCE
+    perf_add_now(&pcontext, "done");
+    perf_print(&pcontext);
+    #endif
+
+    return SYS_ERR_OK;
+}
+
+static void handle_send_completed(void *arg, struct ump_send_queue_entry *entry) {
+    free((void *)entry->header);
+    free((void *)entry->payload);
+    free(entry);
+}
+
+static void send_response(struct block_driver_state *state, errval_t err, size_t payload_size, void *payload) {
+    assert(state != NULL);
+
+    struct block_driver_result *result = malloc(sizeof(struct block_driver_result));
+    if (result == NULL) USER_PANIC("Ran out of memory");
+    struct ump_send_queue_entry *entry = malloc(sizeof(struct ump_send_queue_entry));
+    if (entry == NULL) USER_PANIC("Ran out of memory");
+
+    result->err = err;
+    ump_send(
+        state->send_chan,
+        entry,
+        sizeof(struct block_driver_result),
+        result,
+        payload_size,
+        payload,
+        handle_send_completed,
+        NULL
+    );
+}
+static void send_error_response(struct block_driver_state *state, errval_t err) {
+    assert(state != NULL);
+
+    send_response(state, err, 0, NULL);
+}
+
+static void handle_payload(void *arg, size_t payload_size, void *payload);
+static void handle_request(void *arg, size_t header_size, void *header, size_t payload_size) {
+    assert(arg != NULL);
+
+    errval_t err;
+
+    struct block_driver_state *state = arg;
+    struct block_driver_request *request = header;
+
+    state->current_request = request;
+
+    if (request->bytes > SDHC_BLOCK_SIZE) {
+        send_error_response(state, ERR_INVALID_ARGS);
+    } else if (request->action == BLOCK_DRIVER_ACTION_READ) {
+        // perform read directly
+        void *response_buffer = malloc(request->bytes);
+        if (response_buffer == NULL) USER_PANIC("Ran out of memory");
+
+        err = read_object(request->block_number, request->offset, request->bytes, response_buffer);
+        if (err_is_fail(err)) {
+            send_error_response(state, err);
+        } else {
+            send_response(state, SYS_ERR_OK, request->bytes, response_buffer);
+        }
+    } else if (request->action == BLOCK_DRIVER_ACTION_WRITE) {
+        if (request->bytes != payload_size) {
+            send_error_response(state, ERR_INVALID_ARGS);
+            ump_recv_payload(state->recv_chan, NULL, handle_payload, arg);
+            return;
+        }
+        // we first need to receive the payload before we can handle the request
+        void *payload_buffer = malloc(request->bytes);
+        if (payload_buffer == NULL) USER_PANIC("Ran out of memory");
+        ump_recv_payload(state->recv_chan, payload_buffer, handle_payload, arg);
+        return;
+    } else if (request->action == BLOCK_DRIVER_ACTION_LOCK) {
+        if(locked) {
+            // enqueue the request
+            if (lock_queue_tail != NULL) {
+                lock_queue_tail->next = state;
+            } else {
+                lock_queue_head = state;
+            }
+            lock_queue_tail = state;
+        } else {
+            locked = true;
+            send_error_response(state, SYS_ERR_OK);
+        }
+    } else if (request->action == BLOCK_DRIVER_ACTION_UNLOCK) {
+        if (!locked) USER_PANIC("Received unlock command but was not locked");
+        send_error_response(state, SYS_ERR_OK);
+
+        // send response to first thread on the lock queue if there is one
+        if (lock_queue_head != NULL) {
+            send_error_response(lock_queue_head, SYS_ERR_OK);
+
+            // dequeue the head
+            if (lock_queue_head->next == NULL) {
+                lock_queue_tail = NULL;
+            }
+            lock_queue_head = lock_queue_head->next;
+        } else {
+            locked = false;
+        }
+    } else if (request->action == BLOCK_DRIVER_ACTION_REGISTER_HANDLE) {
+        err = register_handle(request->directory_entry_id);
+        send_error_response(state, err);
+    } else if (request->action == BLOCK_DRIVER_ACTION_UNREGISTER_HANDLE) {
+        err = unregister_handle(request->directory_entry_id);
+        send_error_response(state, err);
+    } else if (request->action == BLOCK_DRIVER_ACTION_COUNT_HANDLES) {
+        size_t *count = malloc(sizeof(size_t));
+        if (count == NULL) {
+            send_error_response(state, LIB_ERR_MALLOC_FAIL);
+        } else {
+            *count = count_handles(request->directory_entry_id);
+            send_response(state, SYS_ERR_OK, sizeof(size_t), count);
+        }
+    } else {
+        send_error_response(state, ERR_INVALID_ARGS);
+    }
+
+    // skip payload
+    ump_recv_payload(state->recv_chan, NULL, handle_payload, arg);
+}
+
+static void handle_payload(void *arg, size_t payload_size, void *payload) {
+    assert(arg != NULL);
+
+    errval_t err;
+
+    struct block_driver_state *state = arg;
+    struct block_driver_request *request = state->current_request;
+
+    // we are guaranteed to have a valid structure request here
+    if (request->action == BLOCK_DRIVER_ACTION_WRITE) {
+        // we got the payload, write it to disk
+        err = write_object(request->block_number, request->offset, request->bytes, payload);
+        send_response(state, err, 0, NULL);
+        // free the payload buffer, we don't use it anymore
+        free(payload);
+    }
+    
+    // listen for the next request on this channel
+    ump_recv_header(state->recv_chan, handle_request, arg);
+}
+
+static errval_t connect_callback(void *arg, struct capref cap) {
+    errval_t err;
+
+    printf("[block_driver_server] incoming connection\n");
+
+    struct ump_send_chan *send_chan;
+    struct ump_recv_chan *recv_chan;
+
+    // we can run the server on the default waitset since we are dispatching on
+    // it for listening to connections anyways
+    err = ump_chan_init(UMP_ROLE_SERVER, &send_chan, &recv_chan, sizeof(struct block_driver_request), cap, get_default_waitset());
+    if (err_is_fail(err)) return err;
+
+    struct block_driver_state *state = malloc(sizeof(struct block_driver_state));
+    if (state == NULL) return LIB_ERR_MALLOC_FAIL;
+    state->recv_chan = recv_chan;
+    state->send_chan = send_chan;
+    ump_recv_header(recv_chan, handle_request, state);
+
+    printf("[block_driver_server] connection ready to receive requests\n");
+
+    return SYS_ERR_OK;
+}
+
+int main(int argc, char *argv[]) {
+
+    errval_t err;
+
+    // get the device capability from the arg cnode
+    struct capref cap_arg0 = {
+        .cnode = cnode_arg,
+        .slot  = 0
+    };
+    // map device registers uncachable
+    void *device_register_vaddr;
+    err = paging_map_frame_attr(
+        get_current_paging_state(),
+        &device_register_vaddr,
+        IMX8X_SDHC_SIZE,
+        cap_arg0,
+        VREGION_FLAGS_READ_WRITE_NOCACHE
+    );
+    if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to map device registers");
+
+    // initialize the sdhc driver
+    printf("[block_driver_server] initializing sdhc driver\n");
+    err = sdhc_init(&sdhc, device_register_vaddr);
+    if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to initialize sdhc driver");
+
+    // create the dma buffer
+    struct capref dma_buffer_frame;
+    size_t size;
+    err = frame_alloc(&dma_buffer_frame, SDHC_BLOCK_SIZE, &size);
+    if(err_is_fail(err)) return err_push(err, LIB_ERR_FRAME_ALLOC);
+
+    // we need the physical address for the DMA read operation
+    struct frame_identity dma_buffer_frame_id;
+    err = frame_identify(dma_buffer_frame, &dma_buffer_frame_id);
+    if (err_is_fail(err)) return err_push(err, LIB_ERR_FRAME_IDENTIFY);
+    dma_buffer_phys = dma_buffer_frame_id.base;
+
+    // map the scratchpad frame for us
+    err = paging_map_frame_attr(get_current_paging_state(), &dma_buffer, size, dma_buffer_frame, VREGION_FLAGS_READ_WRITE);
+    if (err_is_fail(err)) return err_push(err, LIB_ERR_PMAP_MAP);
+
+    printf("[block_driver_server] registering\n");
+    struct ump_binding_server server;
+    err = ump_binding_register(&server, UMP_SERVER_BLOCK_DRIVER, connect_callback, NULL);
+    if (err_is_fail(err)) USER_PANIC_ERR(err, "Failed to register UMP server");
+
+    // wait for connections to the server
+    printf("[block_driver_server] listening\n");
+    struct waitset *default_ws = get_default_waitset();
+    while (true) {
+        err = event_dispatch(default_ws);
+        if (err_is_fail(err)) {
+            DEBUG_ERR(err, "in event_dispatch");
+            abort();
+        }
+    }
+
+    return EXIT_SUCCESS;
+}

usr/init/main.c

@@ -147,6 +147,13 @@ bsp_main(int argc, char *argv[]) {
     waitset_init(&urpc_to_app_ws);
     thread_create(urpc_client_loop, &urpc_to_app_ws);
 
+    // spawn the block driver server
+    struct spawninfo block_driver_si;
+    domainid_t block_driver_pid;
+    err = spawn_load_by_name("block_driver_server", &block_driver_si, &block_driver_pid);
+    if (err_is_fail(err)) {
+        DEBUG_ERR(err, "when spawning block_driver_server");
+    }
 
     // Spawn enet driver
     struct spawninfo enet_si;