[Qemu-devel] [RFC][PATCH v4 06/18] virtagent: add agent_viewfile command

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Utilize the getfile RPC to provide a means to view text files in the
guest. Getfile can handle binary files as well but we don't advertise
that here due to the special handling requiring to store it and provide
it back to the user (base64 encoding it for instance). Hence the
potentially confusing "viewfile" as opposed to "getfile".

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 hmp-commands.hx |   16 +++++++++
 qmp-commands.hx |   33 ++++++++++++++++++
 virtagent.c     |  102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 virtagent.h     |    3 ++
 4 files changed, 154 insertions(+), 0 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index e5585ba..423c752 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1212,6 +1212,22 @@ show available trace events and their state
 ETEXI
 #endif
 
+    {
+        .name       = "agent_viewfile",
+        .args_type  = "filepath:s",
+        .params     = "filepath",
+        .help       = "Echo a file from the guest filesystem",
+        .user_print = do_agent_viewfile_print,
+        .mhandler.cmd_async = do_agent_viewfile,
+        .flags      = MONITOR_CMD_ASYNC,
+    },
+
+STEXI
+@item agent_viewfile @var{filepath}
+@findex agent_viewfile
+Echo the file identified by @var{filepath} on the guest filesystem
+ETEXI
+
 STEXI
 @end table
 ETEXI
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 793cf1c..efa2137 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -738,6 +738,39 @@ Example:
 EQMP
 
     {
+        .name       = "agent_viewfile",
+        .args_type  = "filepath:s",
+        .params     = "filepath",
+        .help       = "Echo a file from the guest filesystem",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_async = do_agent_viewfile,
+        .flags      = MONITOR_CMD_ASYNC,
+    },
+
+STEXI
+@item agent_viewfile @var{filepath}
+@findex agent_viewfile
+Echo the file identified by @var{filepath} on the guest filesystem
+ETEXI
+SQMP
+agent_viewfile
+--------
+
+Echo the file identified by @var{filepath} from the guest filesystem.
+
+Arguments:
+
+- "filepath": Full guest path of the desired file
+
+Example:
+
+-> { "execute": "agent_viewfile",
+                "arguments": { "filepath": "/sys/kernel/kexec_loaded" } }
+<- { "return": { "contents": "0" } }
+
+EQMP
+
+    {
         .name       = "qmp_capabilities",
         .args_type  = "",
         .params     = "",
diff --git a/virtagent.c b/virtagent.c
index 750c167..3fe0a7b 100644
--- a/virtagent.c
+++ b/virtagent.c
@@ -235,3 +235,105 @@ out_callxml:
 out:
     return ret;
 }
+
+/* QMP/HMP RPC client functions */
+
+void do_agent_viewfile_print(Monitor *mon, const QObject *data)
+{
+    QDict *qdict;
+    const char *contents = NULL;
+    int i;
+
+    qdict = qobject_to_qdict(data);
+    if (!qdict_haskey(qdict, "contents")) {
+        return;
+    }
+
+    contents = qdict_get_str(qdict, "contents");
+    if (contents != NULL) {
+         /* monitor_printf truncates so do it in chunks. also, file_contents
+          * may not be null-termed at proper location so explicitly calc
+          * last chunk sizes */
+        for (i = 0; i < strlen(contents); i += 1024) {
+            monitor_printf(mon, "%.1024s", contents + i);
+        }
+    }
+    monitor_printf(mon, "\n");
+}
+
+static void do_agent_viewfile_cb(void *opaque)
+{
+    VARPCData *rpc_data = opaque;
+    xmlrpc_value *resp = NULL;
+    char *file_contents = NULL;
+    size_t file_size;
+    int ret;
+    xmlrpc_env env;
+    QDict *qdict = qdict_new();
+
+    if (rpc_data->status != VA_RPC_STATUS_OK) {
+        LOG("error handling RPC request");
+        goto out_no_resp;
+    }
+
+    xmlrpc_env_init(&env);
+    resp = xmlrpc_parse_response(&env, rpc_data->resp_xml,
+                                 rpc_data->resp_xml_len);
+    if (rpc_has_error(&env)) {
+        ret = -1;
+        goto out_no_resp;
+    }
+
+    xmlrpc_parse_value(&env, resp, "6", &file_contents, &file_size);
+    if (rpc_has_error(&env)) {
+        ret = -1;
+        goto out;
+    }
+
+    if (file_contents != NULL) {
+        qdict_put(qdict, "contents",
+                  qstring_from_substr(file_contents, 0, file_size-1));
+    }
+
+out:
+    xmlrpc_DECREF(resp);
+out_no_resp:
+    rpc_data->mon_cb(rpc_data->mon_data, QOBJECT(qdict));
+}
+
+/*
+ * do_agent_viewfile(): View a text file in the guest
+ */
+int do_agent_viewfile(Monitor *mon, const QDict *mon_params,
+                      MonitorCompletion cb, void *opaque)
+{
+    xmlrpc_env env;
+    xmlrpc_value *params;
+    VARPCData *rpc_data;
+    const char *filepath;
+    int ret;
+
+    filepath = qdict_get_str(mon_params, "filepath");
+    xmlrpc_env_init(&env);
+    params = xmlrpc_build_value(&env, "(s)", filepath);
+    if (rpc_has_error(&env)) {
+        return -1;
+    }
+
+    rpc_data = qemu_mallocz(sizeof(VARPCData));
+    rpc_data->cb = do_agent_viewfile_cb;
+    rpc_data->mon_cb = cb;
+    rpc_data->mon_data = opaque;
+
+    ret = rpc_execute(&env, "getfile", params, rpc_data);
+    if (ret == -EREMOTE) {
+        monitor_printf(mon, "RPC Failed (%i): %s\n", env.fault_code,
+                       env.fault_string);
+        return -1;
+    } else if (ret == -1) {
+        monitor_printf(mon, "RPC communication error\n");
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/virtagent.h b/virtagent.h
index 53efa29..63d77c2 100644
--- a/virtagent.h
+++ b/virtagent.h
@@ -23,5 +23,8 @@
 #define VA_MAX_CHUNK_SIZE 4096 /* max bytes at a time for get/send file */
 
 int va_client_init(VPDriver *vp_drv, bool is_host);
+void do_agent_viewfile_print(Monitor *mon, const QObject *qobject);
+int do_agent_viewfile(Monitor *mon, const QDict *mon_params,
+                      MonitorCompletion cb, void *opaque);
 
 #endif /* VIRTAGENT_H */
-- 
1.7.0.4