[Qemu-devel] [PATCH v3 5/5] qmp: add pmemload command

[Simon Ruderich <simon@ruderich.org>]

Adapted patch from Baojun Wang [1] with the following commit message:

    I found this could be useful to have qemu-softmmu as a cross
    debugger (launch with -s -S command line option), then if we can
    have a command to load guest physical memory, we can use cross gdb
    to do some target debug which gdb cannot do directly.

pmemload is necessary to directly write physical memory which is not
possible with gdb alone as it uses only logical addresses.

The QAPI for pmemload uses "val" as parameter name for the physical
address. This name is not very descriptive but is consistent with the
existing pmemsave. Changing the parameter name of pmemsave is not
possible without breaking the existing API.

[1]: https://lists.gnu.org/archive/html/qemu-trivial/2014-04/msg00074.html

Based-on-patch-by: Baojun Wang <wangbj@gmail.com>
Signed-off-by: Simon Ruderich <simon@ruderich.org>
---
 cpus.c          | 41 +++++++++++++++++++++++++++++++++++++++++
 hmp-commands.hx | 14 ++++++++++++++
 hmp.c           | 12 ++++++++++++
 hmp.h           |  1 +
 qapi/misc.json  | 20 ++++++++++++++++++++
 5 files changed, 88 insertions(+)

diff --git a/cpus.c b/cpus.c
index 49d4d44916..9b105336af 100644
--- a/cpus.c
+++ b/cpus.c
@@ -2367,6 +2367,47 @@ exit:
     qemu_close(fd);
 }
 
+void qmp_pmemload(int64_t addr, int64_t size, int64_t offset,
+                  const char *filename, Error **errp)
+{
+    int fd;
+    size_t l;
+    ssize_t r;
+    uint8_t buf[1024];
+
+    fd = qemu_open(filename, O_RDONLY | O_BINARY);
+    if (fd < 0) {
+        error_setg_file_open(errp, errno, filename);
+        return;
+    }
+    if (offset > 0) {
+        if (lseek(fd, offset, SEEK_SET) != offset) {
+            error_setg_errno(errp, errno,
+                             "could not seek to offset %" PRIx64, offset);
+            goto exit;
+        }
+    }
+
+    while (size != 0) {
+        l = sizeof(buf);
+        if (l > size) {
+            l = size;
+        }
+        r = read(fd, buf, l);
+        if (r <= 0) {
+            error_setg(errp, QERR_IO_ERROR);
+            goto exit;
+        }
+        l = r; /* in case of short read */
+        cpu_physical_memory_write(addr, buf, l);
+        addr += l;
+        size -= l;
+    }
+
+exit:
+    qemu_close(fd);
+}
+
 void qmp_inject_nmi(Error **errp)
 {
     nmi_monitor_handle(monitor_get_cpu_index(), errp);
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 0734fea931..84647c7c1d 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -822,6 +822,20 @@ STEXI
 @item pmemsave @var{addr} @var{size} @var{file}
 @findex pmemsave
 save to disk physical memory dump starting at @var{addr} of size @var{size}.
+ETEXI
+
+    {
+        .name       = "pmemload",
+        .args_type  = "val:l,size:i,offset:i,filename:s",
+        .params     = "addr size offset file",
+        .help       = "load from disk physical memory dump starting at 'addr' of size 'size' at file offset 'offset'",
+        .cmd        = hmp_pmemload,
+    },
+
+STEXI
+@item pmemload @var{addr} @var{size} @var{offset} @var{file}
+@findex pmemload
+load from disk physical memory dump starting at @var{addr} of size @var{size} at file offset @var{offset}.
 ETEXI
 
     {
diff --git a/hmp.c b/hmp.c
index a4d28913bb..b85c943b63 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1105,6 +1105,18 @@ void hmp_pmemsave(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &err);
 }
 
+void hmp_pmemload(Monitor *mon, const QDict *qdict)
+{
+    uint64_t size = qdict_get_int(qdict, "size");
+    uint64_t offset = qdict_get_int(qdict, "offset");
+    const char *filename = qdict_get_str(qdict, "filename");
+    uint64_t addr = qdict_get_int(qdict, "val");
+    Error *err = NULL;
+
+    qmp_pmemload(addr, size, offset, filename, &err);
+    hmp_handle_error(mon, &err);
+}
+
 void hmp_ringbuf_write(Monitor *mon, const QDict *qdict)
 {
     const char *chardev = qdict_get_str(qdict, "device");
diff --git a/hmp.h b/hmp.h
index 20f27439d3..31767ea4a8 100644
--- a/hmp.h
+++ b/hmp.h
@@ -47,6 +47,7 @@ void hmp_system_powerdown(Monitor *mon, const QDict *qdict);
 void hmp_cpu(Monitor *mon, const QDict *qdict);
 void hmp_memsave(Monitor *mon, const QDict *qdict);
 void hmp_pmemsave(Monitor *mon, const QDict *qdict);
+void hmp_pmemload(Monitor *mon, const QDict *qdict);
 void hmp_ringbuf_write(Monitor *mon, const QDict *qdict);
 void hmp_ringbuf_read(Monitor *mon, const QDict *qdict);
 void hmp_cont(Monitor *mon, const QDict *qdict);
diff --git a/qapi/misc.json b/qapi/misc.json
index f5988cc0b5..b4c0065b02 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -1219,6 +1219,26 @@
 { 'command': 'pmemsave',
   'data': {'val': 'int', 'size': 'int', 'filename': 'str'} }
 
+##
+# @pmemload:
+#
+# Load a portion of guest physical memory from a file.
+#
+# @val: the physical address of the guest to start from
+#
+# @size: the size of memory region to load
+#
+# @offset: the offset in the file to start from
+#
+# @filename: the file to load the memory from as binary data
+#
+# Returns: Nothing on success
+#
+# Since: 2.13
+##
+{ 'command': 'pmemload',
+  'data': {'val': 'int', 'size': 'int', 'offset': 'int', 'filename': 'str'} }
+
 ##
 # @cont:
 #
-- 
2.15.0