From: novafacing <rowanbhart@gmail.com>

---
 include/qemu/qemu-plugin.h | 116 +++++++++++++++++++++++++++++++++----
 plugins/api.c              |  66 ++++++++++++++++++++-
 2 files changed, 168 insertions(+), 14 deletions(-)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 0fba36ae02..b812593e7f 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -65,11 +65,18 @@ typedef uint64_t qemu_plugin_id_t;
  *
  * version 4:
  * - added qemu_plugin_read_memory_vaddr
+ *
+ * version 5:
+ * - added qemu_plugin_write_memory_vaddr
+ * - added qemu_plugin_read_memory_hwaddr
+ * - added qemu_plugin_write_memory_hwaddr
+ * - added qemu_plugin_write_register
+ *
  */
 
 extern QEMU_PLUGIN_EXPORT int qemu_plugin_version;
 
-#define QEMU_PLUGIN_VERSION 4
+#define QEMU_PLUGIN_VERSION 5
 
 /**
  * struct qemu_info_t - system information for plugins
@@ -255,8 +262,6 @@ typedef struct {
  * @QEMU_PLUGIN_CB_R_REGS: callback reads the CPU's regs
  * @QEMU_PLUGIN_CB_RW_REGS: callback reads and writes the CPU's regs
  *
- * Note: currently QEMU_PLUGIN_CB_RW_REGS is unused, plugins cannot change
- * system register state.
  */
 enum qemu_plugin_cb_flags {
     QEMU_PLUGIN_CB_NO_REGS,
@@ -893,6 +898,41 @@ typedef struct {
 QEMU_PLUGIN_API
 GArray *qemu_plugin_get_registers(void);
 
+/**
+ * qemu_plugin_read_register() - read register for current vCPU
+ *
+ * @handle: a @qemu_plugin_reg_handle handle
+ * @buf: A GByteArray for the data owned by the plugin
+ *
+ * This function is only available in a context that register read access is
+ * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag.
+ *
+ * Returns the size of the read register. The content of @buf is in target byte
+ * order. On failure returns -1.
+ */
+QEMU_PLUGIN_API
+int qemu_plugin_read_register(struct qemu_plugin_register *handle,
+                              GByteArray *buf);
+
+/**
+ * qemu_plugin_write_register() - write register for current vCPU
+ *
+ * @handle: a @qemu_plugin_reg_handle handle
+ * @buf: A GByteArray for the data owned by the plugin
+ *
+ * This function is only available in a context that register write access is
+ * explicitly requested via the QEMU_PLUGIN_CB_W_REGS flag.
+ *
+ * The size of @buf must be at least the size of the requested register.
+ * Attempting to write a register with @buf smaller than the register size
+ * will result in a crash or other undesired behavior.
+ *
+ * Returns the number of bytes written. On failure returns 0.
+ */
+QEMU_PLUGIN_API
+int qemu_plugin_write_register(struct qemu_plugin_register *handle,
+                              GByteArray *buf);
+
 /**
  * qemu_plugin_read_memory_vaddr() - read from memory using a virtual address
  *
@@ -916,20 +956,72 @@ bool qemu_plugin_read_memory_vaddr(uint64_t addr,
                                    GByteArray *data, size_t len);
 
 /**
- * qemu_plugin_read_register() - read register for current vCPU
+ * qemu_plugin_write_memory_vaddr() - write to memory using a virtual address
  *
- * @handle: a @qemu_plugin_reg_handle handle
- * @buf: A GByteArray for the data owned by the plugin
+ * @addr: A virtual address to write to 
+ * @data: A byte array containing the data to write
  *
- * This function is only available in a context that register read access is
- * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag.
+ * The contents of @data will be written to memory starting at the virtual
+ * address @addr.
  *
- * Returns the size of the read register. The content of @buf is in target byte
- * order. On failure returns -1.
+ * 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 when calling this function in plugin
+ * callbacks to 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
-int qemu_plugin_read_register(struct qemu_plugin_register *handle,
-                              GByteArray *buf);
+bool qemu_plugin_write_memory_vaddr(uint64_t addr,
+                                   GByteArray *data);
+
+/**
+ * qemu_plugin_read_memory_vaddr() - read from memory using a hardware address
+ *
+ * @addr: A virtual address to read from
+ * @data: A byte array to store data into
+ * @len: The number of bytes to read, starting from @addr
+ *
+ * @len bytes of data is read starting at @addr and stored into @data. If @data
+ * is not large enough to hold @len bytes, it will be expanded to the necessary
+ * size, reallocating if necessary. @len must be greater than 0.
+ *
+ * This function does not ensure writes are flushed prior to reading, so
+ * callers should take care when calling this function in plugin callbacks to
+ * avoid attempting to read data which may not yet be written and should use
+ * the memory callback API instead.
+ *
+ * This function is only valid for softmmu targets.
+ *
+ * Returns true on success and false on failure.
+ */
+QEMU_PLUGIN_API
+bool qemu_plugin_read_memory_hwaddr(uint64_t addr,
+                                   GByteArray *data, size_t len);
+
+/**
+ * qemu_plugin_write_memory_vaddr() - write to memory using a hardware 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 hardware
+ * 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 when calling this function in plugin
+ * callbacks to avoid depending on the existence of data written using this
+ * function which may be overwritten afterward.
+ *
+ * This function is only valid for softmmu targets.
+ *
+ * Returns true on success and false on failure.
+ */
+QEMU_PLUGIN_API
+bool qemu_plugin_write_memory_hwaddr(uint64_t addr,
+                                   GByteArray *data);
 
 /**
  * qemu_plugin_scoreboard_new() - alloc a new scoreboard
diff --git a/plugins/api.c b/plugins/api.c
index 24ea64e2de..4a84cf4dfe 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -560,6 +560,24 @@ GArray *qemu_plugin_get_registers(void)
     return create_register_handles(regs);
 }
 
+int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf)
+{
+    g_assert(current_cpu);
+
+    return gdb_read_register(current_cpu, buf, GPOINTER_TO_INT(reg) - 1);
+}
+
+int qemu_plugin_write_register(struct qemu_plugin_register *reg, GByteArray *buf)
+{
+    g_assert(current_cpu);
+
+    if (buf->len == 0) {
+        return 0;
+    }
+
+    return gdb_write_register(current_cpu, buf->data, GPOINTER_TO_INT(reg) - 1);
+}
+
 bool qemu_plugin_read_memory_vaddr(vaddr addr, GByteArray *data, size_t len)
 {
     g_assert(current_cpu);
@@ -580,13 +598,57 @@ bool qemu_plugin_read_memory_vaddr(vaddr addr, GByteArray *data, size_t len)
     return true;
 }
 
-int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf)
+bool qemu_plugin_write_memory_vaddr(vaddr addr, GByteArray *data)
 {
     g_assert(current_cpu);
 
-    return gdb_read_register(current_cpu, buf, GPOINTER_TO_INT(reg) - 1);
+    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;
+}
+
+bool qemu_plugin_read_memory_hwaddr(hwaddr addr, GByteArray *data, size_t len)
+{
+#ifdef CONFIG_SOFTMMU
+    if (len == 0) {
+        return false;
+    }
+
+    g_byte_array_set_size(data, len);
+
+    cpu_physical_memory_rw(addr, data->data, data->len, false);
+
+    return true;
+#else
+    return false;
+#endif
 }
 
+bool qemu_plugin_write_memory_hwaddr(hwaddr addr, GByteArray *data)
+{
+#ifdef CONFIG_SOFTMMU
+    if (data->len == 0) {
+        return false;
+    }
+
+    cpu_physical_memory_rw(addr, data->data, data->len, true);
+
+    return true;
+#else
+    return false;
+#endif
+}
+
+
 struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size)
 {
     return plugin_scoreboard_new(element_size);
-- 
2.46.1

Rowan Hart <rowanbhart@gmail.com> writes:

> From: novafacing <rowanbhart@gmail.com>
>
> ---
>  include/qemu/qemu-plugin.h | 116 +++++++++++++++++++++++++++++++++----
>  plugins/api.c              |  66 ++++++++++++++++++++-
>  2 files changed, 168 insertions(+), 14 deletions(-)
>
> diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
> index 0fba36ae02..b812593e7f 100644
> --- a/include/qemu/qemu-plugin.h
> +++ b/include/qemu/qemu-plugin.h
> @@ -65,11 +65,18 @@ typedef uint64_t qemu_plugin_id_t;
>   *
>   * version 4:
>   * - added qemu_plugin_read_memory_vaddr
> + *
> + * version 5:
> + * - added qemu_plugin_write_memory_vaddr
> + * - added qemu_plugin_read_memory_hwaddr
> + * - added qemu_plugin_write_memory_hwaddr
> + * - added qemu_plugin_write_register
> + *
>   */

In the next version please split up the API additions to make it easier
to review. For now w.r.t. hwaddr I refer to:

  Subject: Re: [PATCH 1/1] plugins: add API to read guest CPU memory from hwaddr
  In-Reply-To: <20240828063224.291503-2-rowanbhart@gmail.com> (Rowan Hart's message of "Tue, 27 Aug 2024 23:32:24 -0700")
  References: <20240828063224.291503-1-rowanbhart@gmail.com> <20240828063224.291503-2-rowanbhart@gmail.com>
  Date: Thu, 09 Jan 2025 11:38:48 +0000
  Message-ID: <877c749pyv.fsf@draig.linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro