plugins: Add memory virtual address write API

This patch adds functions to the plugins API to allow reading and
writing memory via virtual addresses. These functions only permit doing
so on the current CPU, because there is no way to ensure consistency if
plugins are allowed to read or write to other CPUs that aren't currently
in the context of the plugin.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
Message-ID: <20250624175351.440780-5-rowanbhart@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250627112512.1880708-9-alex.bennee@linaro.org>

include/qemu/qemu-plugin.h

@@ -958,6 +958,27 @@ QEMU_PLUGIN_API
 bool qemu_plugin_read_memory_vaddr(uint64_t addr,
                                    GByteArray *data, size_t len);
 
+/**
+ * qemu_plugin_write_memory_vaddr() - write to memory using a virtual address
+ *
+ * @addr: A virtual address to write to
+ * @data: A byte array containing the data to write
+ *
+ * The contents of @data will be written to memory starting at the virtual
+ * address @addr.
+ *
+ * This function does not guarantee consistency of writes, nor does it ensure
+ * that pending writes are flushed either before or after the write takes place,
+ * so callers should take care to only call this function in vCPU context (i.e.
+ * in callbacks) and avoid depending on the existence of data written using this
+ * function which may be overwritten afterward.
+ *
+ * Returns true on success and false on failure.
+ */
+QEMU_PLUGIN_API
+bool qemu_plugin_write_memory_vaddr(uint64_t addr,
+                                   GByteArray *data);
+
 /**
  * qemu_plugin_scoreboard_new() - alloc a new scoreboard
  *

plugins/api.c

@@ -476,6 +476,24 @@ bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
     return true;
 }
 
+bool qemu_plugin_write_memory_vaddr(uint64_t addr, GByteArray *data)
+{
+    g_assert(current_cpu);
+
+    if (data->len == 0) {
+        return false;
+    }
+
+    int result = cpu_memory_rw_debug(current_cpu, addr, data->data,
+                                     data->len, true);
+
+    if (result < 0) {
+        return false;
+    }
+
+    return true;
+}
+
 struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size)
 {
     return plugin_scoreboard_new(element_size);