fw-cfg: support writeable blobs

Useful to send guest data back to QEMU.

Changes from Laszlo Ersek <lersek@redhat.com>:
- rebase the patch from Michael Tsirkin's original postings at [1] and [2]
  to the following patches:
  - loader: Allow a custom AddressSpace when loading ROMs
  - loader: Add AddressSpace loading support to uImages
  - loader: fix handling of custom address spaces when adding ROM blobs
- reject such writes immediately that would exceed the end of the array,
  rather than performing a partial write before setting the error bit: see
  the (len != dma.length) condition
- document the write interface

[1] http://lists.nongnu.org/archive/html/qemu-devel/2016-02/msg04968.html
[2] http://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg02735.html

Cc: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Michael Walle <michael@walle.cc>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Shannon Zhao <zhaoshenglong@huawei.com>
Cc: qemu-arm@nongnu.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Acked-by: Gabriel Somlo <somlo@cmu.edu>
Tested-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

1 files changed, 29 insertions, 8 deletions

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 3ebecb2..e0145c1 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -54,11 +54,13 @@
 #define FW_CFG_DMA_CTL_READ    0x02
 #define FW_CFG_DMA_CTL_SKIP    0x04
 #define FW_CFG_DMA_CTL_SELECT  0x08
+#define FW_CFG_DMA_CTL_WRITE   0x10
 
 #define FW_CFG_DMA_SIGNATURE 0x51454d5520434647ULL /* "QEMU CFG" */
 
 typedef struct FWCfgEntry {
     uint32_t len;
+    bool allow_write;
     uint8_t *data;
     void *callback_opaque;
     FWCfgReadCallback read_callback;
@@ -326,7 +328,7 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
     FWCfgDmaAccess dma;
     int arch;
     FWCfgEntry *e;
-    int read;
+    int read = 0, write = 0;
     dma_addr_t dma_addr;
 
     /* Reset the address before the next access */
@@ -353,8 +355,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
 
     if (dma.control & FW_CFG_DMA_CTL_READ) {
         read = 1;
+        write = 0;
+    } else if (dma.control & FW_CFG_DMA_CTL_WRITE) {
+        read = 0;
+        write = 1;
     } else if (dma.control & FW_CFG_DMA_CTL_SKIP) {
         read = 0;
+        write = 0;
     } else {
         dma.length = 0;
     }
@@ -374,7 +381,9 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
                     dma.control |= FW_CFG_DMA_CTL_ERROR;
                 }
             }
-
+            if (write) {
+                dma.control |= FW_CFG_DMA_CTL_ERROR;
+            }
         } else {
             if (dma.length <= (e->len - s->cur_offset)) {
                 len = dma.length;
@@ -391,6 +400,14 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
                     dma.control |= FW_CFG_DMA_CTL_ERROR;
                 }
             }
+            if (write) {
+                if (!e->allow_write ||
+                    len != dma.length ||
+                    dma_memory_read(s->dma_as, dma.address,
+                                    &e->data[s->cur_offset], len)) {
+                    dma.control |= FW_CFG_DMA_CTL_ERROR;
+                }
+            }
 
             s->cur_offset += len;
         }
@@ -586,7 +603,8 @@ static const VMStateDescription vmstate_fw_cfg = {
 static void fw_cfg_add_bytes_read_callback(FWCfgState *s, uint16_t key,
                                            FWCfgReadCallback callback,
                                            void *callback_opaque,
-                                           void *data, size_t len)
+                                           void *data, size_t len,
+                                           bool read_only)
 {
     int arch = !!(key & FW_CFG_ARCH_LOCAL);
 
@@ -599,6 +617,7 @@ static void fw_cfg_add_bytes_read_callback(FWCfgState *s, uint16_t key,
     s->entries[arch][key].len = (uint32_t)len;
     s->entries[arch][key].read_callback = callback;
     s->entries[arch][key].callback_opaque = callback_opaque;
+    s->entries[arch][key].allow_write = !read_only;
 }
 
 static void *fw_cfg_modify_bytes_read(FWCfgState *s, uint16_t key,
@@ -616,13 +635,14 @@ static void *fw_cfg_modify_bytes_read(FWCfgState *s, uint16_t key,
     s->entries[arch][key].data = data;
     s->entries[arch][key].len = len;
     s->entries[arch][key].callback_opaque = NULL;
+    s->entries[arch][key].allow_write = false;
 
     return ptr;
 }
 
 void fw_cfg_add_bytes(FWCfgState *s, uint16_t key, void *data, size_t len)
 {
-    fw_cfg_add_bytes_read_callback(s, key, NULL, NULL, data, len);
+    fw_cfg_add_bytes_read_callback(s, key, NULL, NULL, data, len, true);
 }
 
 void fw_cfg_add_string(FWCfgState *s, uint16_t key, const char *value)
@@ -749,7 +769,7 @@ static int get_fw_cfg_order(FWCfgState *s, const char *name)
 
 void fw_cfg_add_file_callback(FWCfgState *s,  const char *filename,
                               FWCfgReadCallback callback, void *callback_opaque,
-                              void *data, size_t len)
+                              void *data, size_t len, bool read_only)
 {
     int i, index, count;
     size_t dsize;
@@ -811,7 +831,8 @@ void fw_cfg_add_file_callback(FWCfgState *s,  const char *filename,
     }
 
     fw_cfg_add_bytes_read_callback(s, FW_CFG_FILE_FIRST + index,
-                                   callback, callback_opaque, data, len);
+                                   callback, callback_opaque, data, len,
+                                   read_only);
 
     s->files->f[index].size   = cpu_to_be32(len);
     s->files->f[index].select = cpu_to_be16(FW_CFG_FILE_FIRST + index);
@@ -824,7 +845,7 @@ void fw_cfg_add_file_callback(FWCfgState *s,  const char *filename,
 void fw_cfg_add_file(FWCfgState *s,  const char *filename,
                      void *data, size_t len)
 {
-    fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len);
+    fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len, true);
 }
 
 void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
@@ -847,7 +868,7 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
         }
     }
     /* add new one */
-    fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len);
+    fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len, true);
     return NULL;
 }