[PATCH v13 0/7] Add additional plugin API functions to read and write memory and registers

[PATCH v13 0/7] Add additional plugin API functions to read and write memory and registers

[Rowan Hart]

This patch series adds several new API functions focused on enabling use
cases around reading and writing guest memory from QEMU plugins. To support
these new APIs, some utility functionality around retrieving information about
address spaces is added as well.

The new qemu_plugin_write_register utilizes gdb_write_register, which is now
declared in gdbstub.h for this purpose instead of being static.

qemu_plugin_write_memory_vaddr utilizes cpu_memory_rw_debug much the same as
the existing read_memory_vaddr function does.

The read and write_hwaddr functions are the most different. These functions
use address_space_rw, which works well in most cases. There is an important
caveat that for writes, the page being written will be set dirty by the
write operation. This dirty setting requires locking the page range,
which can contend with an already held lock in page_collection_lock
when called in a tb translate callback with a write to the instruction
memory in the tb. The doc comments warn against doing this, and it's unlikely
anyone would want to do this.

I've also added two test plugins: one that implements a simple hypercall
interface that guest code can use to communicate with the plugin in a
structured way with a test to ensure that this hypercall works and writing
virtual memory works. And one that implements a simple patch utility to patch
memory at runtime. The test for the second plugin ensures the patch applies
successfully to instruction memory, and can use both hw and vaddr methods.

For v3, I've had a few comments from the last submission that I've addressed,
and some that I haven't for one reason or another:

- Enforce QEMU_PLUGIN_CB_ flags in register read/write operations: done!
- Fix my commit messages and add long messages describing commits: done!
- Un-expose AS internals: done! Functions operate on current vCPU, current AS.
- Clean up use of current_cpu: done!
- Make functions take a vcpu_idx: not done. May revisit but it allows footguns.
  Even for translation, seems best to not do this now. We can easily add _vcpu
  versions of these functions in the future if we change our minds!

For v5, I've just updated the enforcement of the QEMU_PLUGIN_CB_ flags to just
use immediate stores, which simplifies the implementation quite a lot and
should be more efficient too. Thanks Pierrick for the suggestion!

v6 is a formatting pass, I left some whitespace that needed removal, some
license text was wrong, and so forth.

v8 reverts a mistake I made extending the size of arrays of TCGHelperInfo
structs, as I misunderstood their sizes. It preserves adding an explicit
zero as the last entry for clarity, however.

v9 fixes qemu_plugin_read_register to return -1 on parameter or flag state
error instead of 0.

In v10, I relaxed the restriction on when the register r/w functions can be
called, allowing all them to be used from any callback where the CPU is not
currently executing, with additional notes in the documentation for exceptions
(atexit and flush, which do not operate on a specific CPU and in which
current_cpu is not set).

v11 makes the cb flags functions inline and fixes a typo where cpu was asserted
but current_cpu was actually accessed.

v12 removes the hypercalls plugin because the functions it tested are also
tested by the patcher plugin, making it redundant. We'll circle back on a
hypercalls API in the future as a part of the plugin API, not as a plugin
itself.

v13 fixes up some issues Alex pointed out with the patch test. Now, the patch
target only runs with libpatch.so, and libpatch.so only runs with the patch
test.

Rowan Hart (1):
  plugins: Add enforcement of QEMU_PLUGIN_CB flags in register R/W
    callbacks

novafacing (6):
  gdbstub: Expose gdb_write_register function to consumers of gdbstub
  plugins: Add register write API
  plugins: Add memory virtual address write API
  plugins: Add memory hardware address read/write API
  plugins: Add patcher plugin and test
  plugins: Update plugin version and add notes

 accel/tcg/plugin-gen.c                    |  30 +++
 gdbstub/gdbstub.c                         |   2 +-
 include/exec/gdbstub.h                    |  14 ++
 include/hw/core/cpu.h                     |   1 +
 include/qemu/plugin.h                     |  15 ++
 include/qemu/qemu-plugin.h                | 176 ++++++++++++++--
 plugins/api.c                             | 135 +++++++++++-
 plugins/core.c                            |  33 +++
 tests/tcg/Makefile.target                 |   7 +-
 tests/tcg/plugins/meson.build             |   2 +-
 tests/tcg/plugins/patch.c                 | 241 ++++++++++++++++++++++
 tests/tcg/x86_64/Makefile.softmmu-target  |   7 +
 tests/tcg/x86_64/system/patch-target.c    |  22 ++
 tests/tcg/x86_64/system/validate-patch.py |  39 ++++
 14 files changed, 705 insertions(+), 19 deletions(-)
 create mode 100644 tests/tcg/plugins/patch.c
 create mode 100644 tests/tcg/x86_64/system/patch-target.c
 create mode 100755 tests/tcg/x86_64/system/validate-patch.py

-- 
2.49.0

[PATCH v13 1/7] gdbstub: Expose gdb_write_register function to consumers of gdbstub

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

This patch exposes the gdb_write_register function from
gdbstub/gdbstub.c via the exec/gdbstub.h header file to support use in
plugins to write register contents.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Julian Ganz <neither@nut.email>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 gdbstub/gdbstub.c      |  2 +-
 include/exec/gdbstub.h | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
index def0b7e877..dd5fb5667c 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -535,7 +535,7 @@ int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg)
     return 0;
 }
 
-static int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg)
+int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg)
 {
     GDBRegisterState *r;
 
diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
index 0675b0b646..a16c0051ce 100644
--- a/include/exec/gdbstub.h
+++ b/include/exec/gdbstub.h
@@ -124,6 +124,20 @@ const GDBFeature *gdb_find_static_feature(const char *xmlname);
  */
 int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
 
+/**
+ * gdb_write_register() - Write a register associated with a CPU.
+ * @cpu: The CPU associated with the register.
+ * @buf: The buffer that the register contents will be set to.
+ * @reg: The register's number returned by gdb_find_feature_register().
+ *
+ * The size of @buf must be at least the size of the register being
+ * written.
+ *
+ * Return: The number of written bytes, or 0 if an error occurred (for
+ * example, an unknown register was provided).
+ */
+int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg);
+
 /**
  * typedef GDBRegDesc - a register description from gdbstub
  */
-- 
2.49.0

[PATCH v13 2/7] plugins: Add register write API

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

This patch adds a function to the plugins API to allow plugins to write
register contents. It also moves the qemu_plugin_read_register function
so all the register-related functions are grouped together in the file.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 include/qemu/qemu-plugin.h | 54 ++++++++++++++++++++++++++------------
 plugins/api.c              | 26 +++++++++++++-----
 2 files changed, 56 insertions(+), 24 deletions(-)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 3a850aa216..cfe1692ecb 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -871,7 +871,8 @@ struct qemu_plugin_register;
 /**
  * typedef qemu_plugin_reg_descriptor - register descriptions
  *
- * @handle: opaque handle for retrieving value with qemu_plugin_read_register
+ * @handle: opaque handle for retrieving value with qemu_plugin_read_register or
+ *          writing value with qemu_plugin_write_register
  * @name: register name
  * @feature: optional feature descriptor, can be NULL
  */
@@ -893,6 +894,41 @@ 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_RW_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
  *
@@ -915,22 +951,6 @@ QEMU_PLUGIN_API
 bool qemu_plugin_read_memory_vaddr(uint64_t addr,
                                    GByteArray *data, size_t len);
 
-/**
- * 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_scoreboard_new() - alloc a new scoreboard
  *
diff --git a/plugins/api.c b/plugins/api.c
index 3c9d4832e9..6514f2c76a 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -433,6 +433,25 @@ 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 || qemu_plugin_get_cb_flags() != QEMU_PLUGIN_CB_RW_REGS) {
+        return -1;
+    }
+
+    return gdb_write_register(current_cpu, buf->data, GPOINTER_TO_INT(reg) - 1);
+}
+
 bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
 {
     g_assert(current_cpu);
@@ -453,13 +472,6 @@ bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
     return true;
 }
 
-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);
-}
-
 struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size)
 {
     return plugin_scoreboard_new(element_size);
-- 
2.49.0

[PATCH v13 3/7] plugins: Add enforcement of QEMU_PLUGIN_CB flags in register R/W callbacks

[Rowan Hart]

This patch adds functionality to enforce the requested QEMU_PLUGIN_CB_
flags level passed when registering a callback function using the
plugins API. Each time a callback is about to be invoked, a thread-local
variable will be updated with the level that callback requested. Then,
called API functions (in particular, the register read and write API)
will call qemu_plugin_get_cb_flags() to check the level is at least the
level they require.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 accel/tcg/plugin-gen.c     | 30 ++++++++++++++++++++++++++++++
 include/hw/core/cpu.h      |  1 +
 include/qemu/plugin.h      | 15 +++++++++++++++
 include/qemu/qemu-plugin.h | 19 +++++++++++++------
 plugins/api.c              |  4 ++++
 plugins/core.c             | 33 +++++++++++++++++++++++++++++++++
 6 files changed, 96 insertions(+), 6 deletions(-)

diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
index c1da753894..9920381a84 100644
--- a/accel/tcg/plugin-gen.c
+++ b/accel/tcg/plugin-gen.c
@@ -117,10 +117,20 @@ static TCGv_i32 gen_cpu_index(void)
 static void gen_udata_cb(struct qemu_plugin_regular_cb *cb)
 {
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call2(cb->f.vcpu_udata, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
 }
 
 static TCGv_ptr gen_plugin_u64_ptr(qemu_plugin_u64 entry)
@@ -173,10 +183,20 @@ static void gen_udata_cond_cb(struct qemu_plugin_conditional_cb *cb)
     tcg_gen_ld_i64(val, ptr, 0);
     tcg_gen_brcondi_i64(cond, val, cb->imm, after_cb);
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call2(cb->f.vcpu_udata, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
     gen_set_label(after_cb);
 
     tcg_temp_free_i64(val);
@@ -210,12 +230,22 @@ static void gen_mem_cb(struct qemu_plugin_regular_cb *cb,
                        qemu_plugin_meminfo_t meminfo, TCGv_i64 addr)
 {
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call4(cb->f.vcpu_mem, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_i32_temp(tcg_constant_i32(meminfo)),
                   tcgv_i64_temp(addr),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
 }
 
 static void inject_cb(struct qemu_plugin_dyn_cb *cb)
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 33296a1c08..162a56a5da 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -368,6 +368,7 @@ typedef struct CPUNegativeOffsetState {
     GArray *plugin_mem_cbs;
     uint64_t plugin_mem_value_low;
     uint64_t plugin_mem_value_high;
+    int32_t plugin_cb_flags;
 #endif
     IcountDecr icount_decr;
     bool can_do_io;
diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h
index 9726a9ebf3..f355c7cb8a 100644
--- a/include/qemu/plugin.h
+++ b/include/qemu/plugin.h
@@ -209,6 +209,21 @@ void qemu_plugin_user_prefork_lock(void);
  */
 void qemu_plugin_user_postfork(bool is_child);
 
+enum qemu_plugin_cb_flags tcg_call_to_qemu_plugin_cb_flags(int flags);
+
+static inline void qemu_plugin_set_cb_flags(CPUState *cpu,
+                                            enum qemu_plugin_cb_flags flags)
+{
+    assert(cpu);
+    cpu->neg.plugin_cb_flags = flags;
+}
+
+static inline enum qemu_plugin_cb_flags qemu_plugin_get_cb_flags(void)
+{
+    assert(current_cpu);
+    return current_cpu->neg.plugin_cb_flags;
+}
+
 #else /* !CONFIG_PLUGIN */
 
 static inline void qemu_plugin_add_opts(void)
diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index cfe1692ecb..9c9ebf6ce0 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -254,9 +254,6 @@ typedef struct {
  * @QEMU_PLUGIN_CB_NO_REGS: callback does not access the CPU's regs
  * @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,
@@ -901,7 +898,12 @@ GArray *qemu_plugin_get_registers(void);
  * @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.
+ * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag, if called inside a
+ * callback that can be registered with a qemu_plugin_cb_flags argument. This
+ * function can also be used in any callback context that does not use a flags
+ * argument, such as in a callback registered with
+ * qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with
+ * qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().
  *
  * Returns the size of the read register. The content of @buf is in target byte
  * order. On failure returns -1.
@@ -916,8 +918,13 @@ int qemu_plugin_read_register(struct qemu_plugin_register *handle,
  * @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_RW_REGS flag.
+ * This function is only available in a context that register read access is
+ * explicitly requested via the QEMU_PLUGIN_CB_RW_REGS flag, if called inside a
+ * callback that can be registered with a qemu_plugin_cb_flags argument. This
+ * function can also be used in any callback context that does not use a flags
+ * argument, such as in a callback registered with
+ * qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with
+ * qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().
  *
  * 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
diff --git a/plugins/api.c b/plugins/api.c
index 6514f2c76a..3f04399c26 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -437,6 +437,10 @@ int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf)
 {
     g_assert(current_cpu);
 
+    if (qemu_plugin_get_cb_flags() == QEMU_PLUGIN_CB_NO_REGS) {
+        return -1;
+    }
+
     return gdb_read_register(current_cpu, buf, GPOINTER_TO_INT(reg) - 1);
 }
 
diff --git a/plugins/core.c b/plugins/core.c
index eb9281fe54..6ae5bbc0ef 100644
--- a/plugins/core.c
+++ b/plugins/core.c
@@ -15,6 +15,7 @@
 #include "qemu/lockable.h"
 #include "qemu/option.h"
 #include "qemu/plugin.h"
+#include "qemu/qemu-plugin.h"
 #include "qemu/queue.h"
 #include "qemu/rcu_queue.h"
 #include "qemu/rcu.h"
@@ -266,7 +267,9 @@ static void qemu_plugin_vcpu_init__async(CPUState *cpu, run_on_cpu_data unused)
     plugin_grow_scoreboards__locked(cpu);
     qemu_rec_mutex_unlock(&plugin.lock);
 
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
     plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_INIT);
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
 }
 
 void qemu_plugin_vcpu_init_hook(CPUState *cpu)
@@ -279,7 +282,9 @@ void qemu_plugin_vcpu_exit_hook(CPUState *cpu)
 {
     bool success;
 
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
     plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_EXIT);
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
 
     assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX);
     qemu_rec_mutex_lock(&plugin.lock);
@@ -367,6 +372,7 @@ void plugin_register_dyn_cb__udata(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_udata_cb_t:
          *   void (*)(uint32_t, void *)
@@ -396,6 +402,7 @@ void plugin_register_dyn_cond_cb__udata(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_udata_cb_t:
          *   void (*)(uint32_t, void *)
@@ -434,6 +441,7 @@ void plugin_register_vcpu_mem_cb(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_mem_cb_t:
          *   void (*)(uint32_t, qemu_plugin_meminfo_t, uint64_t, void *)
@@ -473,7 +481,9 @@ void qemu_plugin_tb_trans_cb(CPUState *cpu, struct qemu_plugin_tb *tb)
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_tb_trans_cb_t func = cb->f.vcpu_tb_trans;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, tb);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -498,7 +508,9 @@ qemu_plugin_vcpu_syscall(CPUState *cpu, int64_t num, uint64_t a1, uint64_t a2,
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_syscall_cb_t func = cb->f.vcpu_syscall;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, cpu->cpu_index, num, a1, a2, a3, a4, a5, a6, a7, a8);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -520,7 +532,9 @@ void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret)
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_syscall_ret_cb_t func = cb->f.vcpu_syscall_ret;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, cpu->cpu_index, num, ret);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -528,14 +542,18 @@ void qemu_plugin_vcpu_idle_cb(CPUState *cpu)
 {
     /* idle and resume cb may be called before init, ignore in this case */
     if (cpu->cpu_index < plugin.num_vcpus) {
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_IDLE);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
 void qemu_plugin_vcpu_resume_cb(CPUState *cpu)
 {
     if (cpu->cpu_index < plugin.num_vcpus) {
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_RESUME);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -615,9 +633,13 @@ void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr,
         switch (cb->type) {
         case PLUGIN_CB_MEM_REGULAR:
             if (rw & cb->regular.rw) {
+                qemu_plugin_set_cb_flags(cpu,
+                    tcg_call_to_qemu_plugin_cb_flags(cb->regular.info->flags));
+
                 cb->regular.f.vcpu_mem(cpu->cpu_index,
                                        make_plugin_meminfo(oi, rw),
                                        vaddr, cb->regular.userp);
+                qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
             }
             break;
         case PLUGIN_CB_INLINE_ADD_U64:
@@ -760,3 +782,14 @@ void plugin_scoreboard_free(struct qemu_plugin_scoreboard *score)
     g_array_free(score->data, TRUE);
     g_free(score);
 }
+
+enum qemu_plugin_cb_flags tcg_call_to_qemu_plugin_cb_flags(int flags)
+{
+    if (flags & TCG_CALL_NO_RWG) {
+        return QEMU_PLUGIN_CB_NO_REGS;
+    } else if (flags & TCG_CALL_NO_WG) {
+        return QEMU_PLUGIN_CB_R_REGS;
+    } else {
+        return QEMU_PLUGIN_CB_RW_REGS;
+    }
+}
\ No newline at end of file
-- 
2.49.0

[PATCH v13 4/7] plugins: Add memory virtual address write API

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

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>
---
 include/qemu/qemu-plugin.h | 21 +++++++++++++++++++++
 plugins/api.c              | 18 ++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 9c9ebf6ce0..4167c46c2a 100644
--- a/include/qemu/qemu-plugin.h
+++ b/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
  *
diff --git a/plugins/api.c b/plugins/api.c
index 3f04399c26..1f64a9ea64 100644
--- a/plugins/api.c
+++ b/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);
-- 
2.49.0

[PATCH v13 5/7] plugins: Add memory hardware address read/write API

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

This patch adds functions to the plugins API to allow plugins to read
and write memory via hardware addresses. The functions use the current
address space of the current CPU in order to avoid exposing address
space information to users. A later patch may want to add a function to
permit a specified address space, for example to facilitate
architecture-specific plugins that want to operate on them, for example
reading ARM secure memory.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 include/qemu/qemu-plugin.h | 93 ++++++++++++++++++++++++++++++++++++
 plugins/api.c              | 97 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 190 insertions(+)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 4167c46c2a..5eecdccc67 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -979,6 +979,99 @@ QEMU_PLUGIN_API
 bool qemu_plugin_write_memory_vaddr(uint64_t addr,
                                    GByteArray *data);
 
+/**
+ * enum qemu_plugin_hwaddr_operation_result - result of a memory operation
+ *
+ * @QEMU_PLUGIN_HWADDR_OPERATION_OK: hwaddr operation succeeded
+ * @QEMU_PLUGIN_HWADDR_OPERATION_ERROR: unexpected error occurred
+ * @QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR: error in memory device
+ * @QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED: permission error
+ * @QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS: address was invalid
+ * @QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE: invalid address space
+ */
+enum qemu_plugin_hwaddr_operation_result {
+    QEMU_PLUGIN_HWADDR_OPERATION_OK,
+    QEMU_PLUGIN_HWADDR_OPERATION_ERROR,
+    QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR,
+    QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED,
+    QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS,
+    QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE,
+};
+
+/**
+ * qemu_plugin_read_memory_hwaddr() - read from memory using a hardware address
+ *
+ * @addr: The physical 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 from the current memory space for the current
+ * vCPU 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 a qemu_plugin_hwaddr_operation_result indicating the result of the
+ * operation.
+ */
+QEMU_PLUGIN_API
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_read_memory_hwaddr(uint64_t addr, GByteArray *data, size_t len);
+
+/**
+ * qemu_plugin_write_memory_hwaddr() - write to memory using a hardware address
+ *
+ * @addr: A physical 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 in the current address space for the current vCPU.
+ *
+ * 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. In addition, this function requires that the
+ * pages containing the address are not locked. Practically, this means that you
+ * should not write instruction memory in a current translation block inside a
+ * callback registered with qemu_plugin_register_vcpu_tb_trans_cb.
+ *
+ * You can, for example, write instruction memory in a current translation block
+ * in a callback registered with qemu_plugin_register_vcpu_tb_exec_cb, although
+ * be aware that the write will not be flushed until after the translation block
+ * has finished executing.  In general, this function should be used to write
+ * data memory or to patch code at a known address, not in a current translation
+ * block.
+ *
+ * This function is only valid for softmmu targets.
+ *
+ * Returns a qemu_plugin_hwaddr_operation_result indicating the result of the
+ * operation.
+ */
+QEMU_PLUGIN_API
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_write_memory_hwaddr(uint64_t addr, GByteArray *data);
+
+/**
+ * qemu_plugin_translate_vaddr() - translate virtual address for current vCPU
+ *
+ * @vaddr: virtual address to translate
+ * @hwaddr: pointer to store the physical address
+ *
+ * This function is only valid in vCPU context (i.e. in callbacks) and is only
+ * valid for softmmu targets.
+ *
+ * Returns true on success and false on failure.
+ */
+QEMU_PLUGIN_API
+bool qemu_plugin_translate_vaddr(uint64_t vaddr, uint64_t *hwaddr);
+
 /**
  * qemu_plugin_scoreboard_new() - alloc a new scoreboard
  *
diff --git a/plugins/api.c b/plugins/api.c
index 1f64a9ea64..eac04cc1f6 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -39,6 +39,7 @@
 #include "qemu/main-loop.h"
 #include "qemu/plugin.h"
 #include "qemu/log.h"
+#include "system/memory.h"
 #include "tcg/tcg.h"
 #include "exec/gdbstub.h"
 #include "exec/target_page.h"
@@ -494,6 +495,102 @@ bool qemu_plugin_write_memory_vaddr(uint64_t addr, GByteArray *data)
     return true;
 }
 
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_read_memory_hwaddr(hwaddr addr, GByteArray *data, size_t len)
+{
+#ifdef CONFIG_SOFTMMU
+    if (len == 0) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+
+    g_assert(current_cpu);
+
+
+    int as_idx = cpu_asidx_from_attrs(current_cpu, MEMTXATTRS_UNSPECIFIED);
+    AddressSpace *as = cpu_get_address_space(current_cpu, as_idx);
+
+    if (as == NULL) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE;
+    }
+
+    g_byte_array_set_size(data, len);
+    MemTxResult res = address_space_rw(as, addr,
+                                       MEMTXATTRS_UNSPECIFIED, data->data,
+                                       data->len, false);
+
+    switch (res) {
+    case MEMTX_OK:
+        return QEMU_PLUGIN_HWADDR_OPERATION_OK;
+    case MEMTX_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR;
+    case MEMTX_DECODE_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS;
+    case MEMTX_ACCESS_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED;
+    default:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+#else
+    return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+#endif
+}
+
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_write_memory_hwaddr(hwaddr addr, GByteArray *data)
+{
+#ifdef CONFIG_SOFTMMU
+    if (data->len == 0) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+
+    g_assert(current_cpu);
+
+    int as_idx = cpu_asidx_from_attrs(current_cpu, MEMTXATTRS_UNSPECIFIED);
+    AddressSpace *as = cpu_get_address_space(current_cpu, as_idx);
+
+    if (as == NULL) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE;
+    }
+
+    MemTxResult res = address_space_rw(as, addr,
+                                       MEMTXATTRS_UNSPECIFIED, data->data,
+                                       data->len, true);
+    switch (res) {
+    case MEMTX_OK:
+        return QEMU_PLUGIN_HWADDR_OPERATION_OK;
+    case MEMTX_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR;
+    case MEMTX_DECODE_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS;
+    case MEMTX_ACCESS_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED;
+    default:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+#else
+    return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+#endif
+}
+
+bool qemu_plugin_translate_vaddr(uint64_t vaddr, uint64_t *hwaddr)
+{
+#ifdef CONFIG_SOFTMMU
+    g_assert(current_cpu);
+
+    uint64_t res = cpu_get_phys_page_debug(current_cpu, vaddr);
+
+    if (res == (uint64_t)-1) {
+        return false;
+    }
+
+    *hwaddr = res | (vaddr & ~TARGET_PAGE_MASK);
+
+    return true;
+#else
+    return false;
+#endif
+}
+
 struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size)
 {
     return plugin_scoreboard_new(element_size);
-- 
2.49.0

[PATCH v13 6/7] plugins: Add patcher plugin and test

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

This patch adds a plugin that exercises the virtual and hardware memory
read-write API functions added in a previous patch. The plugin takes a
target and patch byte sequence, and will overwrite any instruction
matching the target byte sequence with the patch.

Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 tests/tcg/Makefile.target                 |   7 +-
 tests/tcg/plugins/meson.build             |   2 +-
 tests/tcg/plugins/patch.c                 | 241 ++++++++++++++++++++++
 tests/tcg/x86_64/Makefile.softmmu-target  |   7 +
 tests/tcg/x86_64/system/patch-target.c    |  22 ++
 tests/tcg/x86_64/system/validate-patch.py |  39 ++++
 6 files changed, 316 insertions(+), 2 deletions(-)
 create mode 100644 tests/tcg/plugins/patch.c
 create mode 100644 tests/tcg/x86_64/system/patch-target.c
 create mode 100755 tests/tcg/x86_64/system/validate-patch.py

diff --git a/tests/tcg/Makefile.target b/tests/tcg/Makefile.target
index 95ff76ea44..af68f11664 100644
--- a/tests/tcg/Makefile.target
+++ b/tests/tcg/Makefile.target
@@ -151,7 +151,12 @@ ifeq ($(CONFIG_PLUGIN),y)
 PLUGIN_SRC=$(SRC_PATH)/tests/tcg/plugins
 PLUGIN_LIB=../plugins
 VPATH+=$(PLUGIN_LIB)
-PLUGINS=$(patsubst %.c, lib%.so, $(notdir $(wildcard $(PLUGIN_SRC)/*.c)))
+# Some plugins need to be disabled for all tests to avoid exponential explosion.
+# For example, libpatch.so only needs to run against the arch-specific patch
+# target test, so we explicitly run it in the arch-specific Makefile.
+DISABLE_PLUGINS=libpatch.so
+PLUGINS=$(filter-out $(DISABLE_PLUGINS), \
+	$(patsubst %.c, lib%.so, $(notdir $(wildcard $(PLUGIN_SRC)/*.c))))
 
 # We need to ensure expand the run-plugin-TEST-with-PLUGIN
 # pre-requistes manually here as we can't use stems to handle it. We
diff --git a/tests/tcg/plugins/meson.build b/tests/tcg/plugins/meson.build
index 41f02f2c7f..163042e601 100644
--- a/tests/tcg/plugins/meson.build
+++ b/tests/tcg/plugins/meson.build
@@ -1,6 +1,6 @@
 t = []
 if get_option('plugins')
-  foreach i : ['bb', 'empty', 'inline', 'insn', 'mem', 'reset', 'syscall']
+  foreach i : ['bb', 'empty', 'inline', 'insn', 'mem', 'reset', 'syscall', 'patch']
     if host_os == 'windows'
       t += shared_module(i, files(i + '.c') + '../../../contrib/plugins/win32_linker.c',
                         include_directories: '../../../include/qemu',
diff --git a/tests/tcg/plugins/patch.c b/tests/tcg/plugins/patch.c
new file mode 100644
index 0000000000..450fc51c88
--- /dev/null
+++ b/tests/tcg/plugins/patch.c
@@ -0,0 +1,241 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This plugin patches instructions matching a pattern to a different
+ * instruction as they execute
+ *
+ */
+
+#include "glib.h"
+#include "glibconfig.h"
+
+#include <qemu-plugin.h>
+#include <string.h>
+#include <stdio.h>
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+static bool use_hwaddr;
+static GByteArray *target_data;
+static GByteArray *patch_data;
+
+/**
+ * Parse a string of hexadecimal digits into a GByteArray. The string must be
+ * even length
+ */
+static GByteArray *str_to_bytes(const char *str)
+{
+    size_t len = strlen(str);
+
+    if (len == 0 || len % 2 != 0) {
+        return NULL;
+    }
+
+    GByteArray *bytes = g_byte_array_new();
+    char byte[3] = {0};
+    guint8 value = 0;
+
+    for (size_t i = 0; i < len; i += 2) {
+        byte[0] = str[i];
+        byte[1] = str[i + 1];
+        value = (guint8)g_ascii_strtoull(byte, NULL, 16);
+        g_byte_array_append(bytes, &value, 1);
+    }
+
+    return bytes;
+}
+
+static void patch_hwaddr(unsigned int vcpu_index, void *userdata)
+{
+    uint64_t addr = (uint64_t)userdata;
+    g_autoptr(GString) str = g_string_new(NULL);
+    g_string_printf(str, "patching: @0x%"
+                    PRIx64 "\n",
+                    addr);
+    qemu_plugin_outs(str->str);
+
+    enum qemu_plugin_hwaddr_operation_result result =
+        qemu_plugin_write_memory_hwaddr(addr, patch_data);
+
+
+    if (result != QEMU_PLUGIN_HWADDR_OPERATION_OK) {
+        g_autoptr(GString) errmsg = g_string_new(NULL);
+        g_string_printf(errmsg, "Failed to write memory: %d\n", result);
+        qemu_plugin_outs(errmsg->str);
+        return;
+    }
+
+    GByteArray *read_data = g_byte_array_new();
+
+    result = qemu_plugin_read_memory_hwaddr(addr, read_data,
+                                            patch_data->len);
+
+    qemu_plugin_outs("Reading memory...\n");
+
+    if (result != QEMU_PLUGIN_HWADDR_OPERATION_OK) {
+        g_autoptr(GString) errmsg = g_string_new(NULL);
+        g_string_printf(errmsg, "Failed to read memory: %d\n", result);
+        qemu_plugin_outs(errmsg->str);
+        return;
+    }
+
+    if (memcmp(patch_data->data, read_data->data, patch_data->len) != 0) {
+        qemu_plugin_outs("Failed to read back written data\n");
+    }
+
+    qemu_plugin_outs("Success!\n");
+
+    return;
+}
+
+static void patch_vaddr(unsigned int vcpu_index, void *userdata)
+{
+    uint64_t addr = (uint64_t)userdata;
+    uint64_t hwaddr = 0;
+    if (!qemu_plugin_translate_vaddr(addr, &hwaddr)) {
+        qemu_plugin_outs("Failed to translate vaddr\n");
+        return;
+    }
+    g_autoptr(GString) str = g_string_new(NULL);
+    g_string_printf(str, "patching: @0x%"
+                    PRIx64 " hw: @0x%" PRIx64 "\n",
+                    addr, hwaddr);
+    qemu_plugin_outs(str->str);
+
+    qemu_plugin_outs("Writing memory (vaddr)...\n");
+
+    if (!qemu_plugin_write_memory_vaddr(addr, patch_data)) {
+        qemu_plugin_outs("Failed to write memory\n");
+        return;
+    }
+
+    qemu_plugin_outs("Reading memory (vaddr)...\n");
+
+    g_autoptr(GByteArray) read_data = g_byte_array_new();
+
+    if (!qemu_plugin_read_memory_vaddr(addr, read_data, patch_data->len)) {
+        qemu_plugin_outs("Failed to read memory\n");
+        return;
+    }
+
+    if (memcmp(patch_data->data, read_data->data, patch_data->len) != 0) {
+        qemu_plugin_outs("Failed to read back written data\n");
+    }
+
+    qemu_plugin_outs("Success!\n");
+
+    return;
+}
+
+/*
+ * Callback on translation of a translation block.
+ */
+static void vcpu_tb_trans_cb(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
+{
+    uint64_t addr = 0;
+    g_autoptr(GByteArray) insn_data = g_byte_array_new();
+    for (size_t i = 0; i < qemu_plugin_tb_n_insns(tb); i++) {
+        struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
+
+        if (use_hwaddr) {
+            uint64_t vaddr = qemu_plugin_insn_vaddr(insn);
+            if (!qemu_plugin_translate_vaddr(vaddr, &addr)) {
+                qemu_plugin_outs("Failed to translate vaddr\n");
+                continue;
+            }
+        } else {
+            addr = qemu_plugin_insn_vaddr(insn);
+        }
+
+        g_byte_array_set_size(insn_data, qemu_plugin_insn_size(insn));
+        qemu_plugin_insn_data(insn, insn_data->data, insn_data->len);
+
+        if (insn_data->len >= target_data->len &&
+            !memcmp(insn_data->data, target_data->data,
+                    MIN(target_data->len, insn_data->len))) {
+            if (use_hwaddr) {
+                qemu_plugin_register_vcpu_tb_exec_cb(tb, patch_hwaddr,
+                                                     QEMU_PLUGIN_CB_NO_REGS,
+                                                     (void *)addr);
+            } else {
+                qemu_plugin_register_vcpu_tb_exec_cb(tb, patch_vaddr,
+                                                     QEMU_PLUGIN_CB_NO_REGS,
+                                                     (void *)addr);
+            }
+        }
+    }
+}
+
+static void usage(void)
+{
+    fprintf(stderr, "Usage: <lib>,target=<bytes>,patch=<new_bytes>"
+            "[,use_hwaddr=true|false]");
+}
+
+/*
+ * Called when the plugin is installed
+ */
+QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
+                                           const qemu_info_t *info, int argc,
+                                           char **argv)
+{
+
+    use_hwaddr = true;
+    target_data = NULL;
+    patch_data = NULL;
+
+    if (argc > 4) {
+        usage();
+        return -1;
+    }
+
+    for (size_t i = 0; i < argc; i++) {
+        char *opt = argv[i];
+        g_auto(GStrv) tokens = g_strsplit(opt, "=", 2);
+        if (g_strcmp0(tokens[0], "use_hwaddr") == 0) {
+            if (!qemu_plugin_bool_parse(tokens[0], tokens[1], &use_hwaddr)) {
+                fprintf(stderr,
+                        "Failed to parse boolean argument use_hwaddr\n");
+                return -1;
+            }
+        } else if (g_strcmp0(tokens[0], "target") == 0) {
+            target_data = str_to_bytes(tokens[1]);
+            if (!target_data) {
+                fprintf(stderr,
+                         "Failed to parse target bytes.\n");
+                return -1;
+            }
+        } else if (g_strcmp0(tokens[0], "patch") == 0) {
+            patch_data = str_to_bytes(tokens[1]);
+            if (!patch_data) {
+                fprintf(stderr, "Failed to parse patch bytes.\n");
+                return -1;
+            }
+        } else {
+            fprintf(stderr, "Unknown argument: %s\n", tokens[0]);
+            usage();
+            return -1;
+        }
+    }
+
+    if (!target_data) {
+        fprintf(stderr, "target argument is required\n");
+        usage();
+        return -1;
+    }
+
+    if (!patch_data) {
+        fprintf(stderr, "patch argument is required\n");
+        usage();
+        return -1;
+    }
+
+    if (target_data->len != patch_data->len) {
+        fprintf(stderr, "Target and patch data must be the same length\n");
+        return -1;
+    }
+
+    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans_cb);
+
+    return 0;
+}
diff --git a/tests/tcg/x86_64/Makefile.softmmu-target b/tests/tcg/x86_64/Makefile.softmmu-target
index ef6bcb4dc7..819165ae36 100644
--- a/tests/tcg/x86_64/Makefile.softmmu-target
+++ b/tests/tcg/x86_64/Makefile.softmmu-target
@@ -35,3 +35,10 @@ memory: CFLAGS+=-DCHECK_UNALIGNED=1
 
 # Running
 QEMU_OPTS+=-device isa-debugcon,chardev=output -device isa-debug-exit,iobase=0xf4,iosize=0x4 -kernel
+
+run-plugin-patch-target-with-libpatch.so:		\
+	PLUGIN_ARGS=$(COMMA)target=ffc0$(COMMA)patch=9090$(COMMA)use_hwaddr=true
+run-plugin-patch-target-with-libpatch.so:		\
+	CHECK_PLUGIN_OUTPUT_COMMAND=$(X64_SYSTEM_SRC)/validate-patch.py $@.out
+run-plugin-patch-target-with-libpatch.so: patch-target libpatch.so
+EXTRA_RUNS+=run-plugin-patch-target-with-libpatch.so
\ No newline at end of file
diff --git a/tests/tcg/x86_64/system/patch-target.c b/tests/tcg/x86_64/system/patch-target.c
new file mode 100644
index 0000000000..8c2b6f4ba7
--- /dev/null
+++ b/tests/tcg/x86_64/system/patch-target.c
@@ -0,0 +1,22 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This test target increments a value 100 times. The patcher converts the
+ * inc instruction to a nop, so it only increments the value once.
+ *
+ */
+#include <minilib.h>
+
+int main(void)
+{
+    ml_printf("Running test...\n");
+    unsigned int x = 0;
+    for (int i = 0; i < 100; i++) {
+        asm volatile (
+            "inc %[x]"
+            : [x] "+a" (x)
+        );
+    }
+    ml_printf("Value: %d\n", x);
+    return 0;
+}
diff --git a/tests/tcg/x86_64/system/validate-patch.py b/tests/tcg/x86_64/system/validate-patch.py
new file mode 100755
index 0000000000..700950eae5
--- /dev/null
+++ b/tests/tcg/x86_64/system/validate-patch.py
@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+#
+# validate-patch.py: check the patch applies
+#
+# This program takes two inputs:
+#   - the plugin output
+#   - the binary output
+#
+# Copyright (C) 2024
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import sys
+from argparse import ArgumentParser
+
+def main() -> None:
+    """
+    Process the arguments, injest the program and plugin out and
+    verify they match up and report if they do not.
+    """
+    parser = ArgumentParser(description="Validate patch")
+    parser.add_argument('test_output',
+                        help="The output from the test itself")
+    parser.add_argument('plugin_output',
+                        help="The output from plugin")
+    args = parser.parse_args()
+
+    with open(args.test_output, 'r') as f:
+        test_data = f.read()
+    with open(args.plugin_output, 'r') as f:
+        plugin_data = f.read()
+    if "Value: 1" in test_data:
+        sys.exit(0)
+    else:
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()
+
-- 
2.49.0

[PATCH v13 7/7] plugins: Update plugin version and add notes

[Rowan Hart]

From: novafacing <rowanbhart@gmail.com>

This patch updates the plugin version to gate new APIs and adds notes
describing what has been added.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Rowan Hart <rowanbhart@gmail.com>
---
 include/qemu/qemu-plugin.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 5eecdccc67..c450106af1 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
+ * - added qemu_plugin_translate_vaddr
  */
 
 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
-- 
2.49.0

Re: [PATCH v13 0/7] Add additional plugin API functions to read and write memory and registers

[Alex Bennée]

Rowan Hart <rowanbhart@gmail.com> writes:

> This patch series adds several new API functions focused on enabling use
> cases around reading and writing guest memory from QEMU plugins. To support
> these new APIs, some utility functionality around retrieving information about
> address spaces is added as well.

I think we are almost there but I ran into a problem with the test:

  ➜  make run-tcg-tests-x86_64-softmmu
    BUILD   x86_64-softmmu guest-tests
    RUN     x86_64-softmmu guest-tests
    TEST    hello on x86_64
    TEST    interrupt on x86_64
    TEST    memory on x86_64
    TEST    hello-with-libbb.so on x86_64
    TEST    interrupt-with-libbb.so on x86_64
    TEST    memory-with-libbb.so on x86_64
    TEST    hello-with-libempty.so on x86_64
    TEST    interrupt-with-libempty.so on x86_64
    TEST    memory-with-libempty.so on x86_64
    TEST    hello-with-libinline.so on x86_64
    TEST    interrupt-with-libinline.so on x86_64
    TEST    memory-with-libinline.so on x86_64
    TEST    hello-with-libinsn.so on x86_64
    TEST    interrupt-with-libinsn.so on x86_64
    TEST    memory-with-libinsn.so on x86_64
    TEST    hello-with-libmem.so on x86_64
    TEST    interrupt-with-libmem.so on x86_64
    TEST    memory-with-libmem.so on x86_64
    TEST    check plugin libmem.so output with memory
    TEST    hello-with-libreset.so on x86_64
    TEST    interrupt-with-libreset.so on x86_64
    TEST    memory-with-libreset.so on x86_64
    TEST    hello-with-libsyscall.so on x86_64
    TEST    interrupt-with-libsyscall.so on x86_64
    TEST    memory-with-libsyscall.so on x86_64
    TEST    softmmu gdbstub support on x86_64
  qemu-system-x86_64: -gdb unix:path=/tmp/tmp01eq35b3qemu-gdbstub/gdbstub.socket,server=on: info: QEMU waiting for connection on: disconnected:unix:/tmp/tmp01eq35b3qemu-gdbstub/gdbstub.socket,server=on
  qemu-system-x86_64: QEMU: Terminated via GDBstub
    TEST    softmmu gdbstub support on x86_64
  qemu-system-x86_64: -gdb unix:path=/tmp/tmp4wf7k1fwqemu-gdbstub/gdbstub.socket,server=on: info: QEMU waiting for connection on: disconnected:unix:/tmp/tmp4wf7k1fwqemu-gdbstub/gdbstub.socket,server=on
  qemu-system-x86_64: QEMU: Terminated via GDBstub
    TEST    softmmu gdbstub untimely packets on x86_64
  qemu-system-x86_64: -gdb unix:path=/tmp/tmpnagp6w_mqemu-gdbstub/gdbstub.socket,server=on: info: QEMU waiting for connection on: disconnected:unix:/tmp/tmpnagp6w_mqemu-gdbstub/gdbstub.socket,server=on
    GREP    file untimely-packet.gdb.err
    TEST    softmmu gdbstub support on x86_64
  qemu-system-x86_64: -gdb unix:path=/tmp/tmpnkn1fbmsqemu-gdbstub/gdbstub.socket,server=on: info: QEMU waiting for connection on: disconnected:unix:/tmp/tmpnkn1fbmsqemu-gdbstub/gdbstub.socket,server=on
  qemu-system-x86_64: QEMU: Terminated via GDBstub
  make[1]: *** No rule to make target 'patch-target', needed by 'run-plugin-patch-target-with-libpatch.so'.  Stop.
  make: *** [/home/alex/lsrc/qemu.git/tests/Makefile.include:56: run-tcg-tests-x86_64-softmmu] Error 2

You need to ensure vpath is set, something like:

modified   tests/tcg/x86_64/Makefile.softmmu-target
@@ -1,13 +1,11 @@
 #
-# x86 system tests
-#
-# This currently builds only for i386. The common C code is built
-# with standard compiler flags however so we can support both by
-# adding additional boot files for x86_64.
+# x86-64 system tests
 #
 
-I386_SYSTEM_SRC=$(SRC_PATH)/tests/tcg/i386/system
 X64_SYSTEM_SRC=$(SRC_PATH)/tests/tcg/x86_64/system
+X64_SYSTEM_TESTS= $(patsubst $(X64_SYSTEM_SRC)/%.c, %, $(wildcard $(X64_SYSTEM_SRC)/*.c))
+
+VPATH+=$(X64_SYSTEM_SRC)
 
 # These objects provide the basic boot code and helper functions for all tests
 CRT_OBJS=boot.o
@@ -18,7 +16,7 @@ LDFLAGS=-Wl,-T$(LINK_SCRIPT) -Wl,-melf_x86_64
 CFLAGS+=-nostdlib -ggdb -O0 $(MINILIB_INC)
 LDFLAGS+=-static -nostdlib $(CRT_OBJS) $(MINILIB_OBJS) -lgcc
 
-TESTS+=$(MULTIARCH_TESTS)
+TESTS+=$(X64_SYSTEM_TESTS) $(MULTIARCH_TESTS)
 EXTRA_RUNS+=$(MULTIARCH_RUNS)
 
 # building head blobs
@@ -41,4 +39,4 @@ run-plugin-patch-target-with-libpatch.so:		\
 run-plugin-patch-target-with-libpatch.so:		\
 	CHECK_PLUGIN_OUTPUT_COMMAND=$(X64_SYSTEM_SRC)/validate-patch.py $@.out
 run-plugin-patch-target-with-libpatch.so: patch-target libpatch.so
-EXTRA_RUNS+=run-plugin-patch-target-with-libpatch.so
\ No newline at end of file
+EXTRA_RUNS+=run-plugin-patch-target-with-libpatch.so

<snip>
>
> Rowan Hart (1):
>   plugins: Add enforcement of QEMU_PLUGIN_CB flags in register R/W
>     callbacks
>
> novafacing (6):
>   gdbstub: Expose gdb_write_register function to consumers of gdbstub
>   plugins: Add register write API
>   plugins: Add memory virtual address write API
>   plugins: Add memory hardware address read/write API
>   plugins: Add patcher plugin and test
>   plugins: Update plugin version and add notes

Could you update the Author fields so the Author matches the s-o-b tags
please and is consistent please.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH v13 0/7] Add additional plugin API functions to read and write memory and registers

[Rowan Hart]

>    make[1]: *** No rule to make target 'patch-target', needed by 'run-plugin-patch-target-with-libpatch.so'.  Stop.
>    make: *** [/home/alex/lsrc/qemu.git/tests/Makefile.include:56: run-tcg-tests-x86_64-softmmu] Error 2
>
> You need to ensure vpath is set, something like:
Thanks for the note Alex. It turns out I'd been testing like `make -C 
build -j$(nproc) run-tcg-tests-x86_64-softmmu`, making this succeed when 
it shouldn't have. I updated it in v14.

> novafacing (6):
>    gdbstub: Expose gdb_write_register function to consumers of gdbstub
>    plugins: Add register write API
>    plugins: Add memory virtual address write API
>    plugins: Add memory hardware address read/write API
>    plugins: Add patcher plugin and test
>    plugins: Update plugin version and add notes
> Could you update the Author fields so the Author matches the s-o-b tags
> please and is consistent please.

Absolutely, fixed this in v14 as well. One of my computers must have had 
my alias set instead of real name, apologies!

-Rowan