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Iglesias" , Bin Meng , Laurent Vivier , Palmer Dabbelt , Daniel Henrique Barboza , Alistair Francis , Akihiko Odaki Subject: [PATCH v3 21/27] plugins: add an API to read registers Date: Mon, 26 Feb 2024 16:56:40 +0000 Message-Id: <20240226165646.425600-22-alex.bennee@linaro.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240226165646.425600-1-alex.bennee@linaro.org> References: <20240226165646.425600-1-alex.bennee@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::235; envelope-from=alex.bennee@linaro.org; helo=mail-lj1-x235.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org We can only request a list of registers once the vCPU has been initialised so the user needs to use either call the get function on vCPU initialisation or during the translation phase. We don't expose the reg number to the plugin instead hiding it behind an opaque handle. For now this is just the gdb_regnum encapsulated in an anonymous GPOINTER but in future as we add more state for plugins to track we can expand it. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1706 Cc: Akihiko Odaki Message-Id: <20240103173349.398526-39-alex.bennee@linaro.org> Based-on: <20231025093128.33116-18-akihiko.odaki@daynix.com> Signed-off-by: Alex Bennée Reviewed-by: Pierrick Bouvier --- v4 - the get/read_registers functions are now implicitly for current vCPU only to accidental cpu != current_cpu uses. v5 - make reg_handles as per-CPUPluginState variable. v6 - for now just wrap gdb_regnum --- include/qemu/qemu-plugin.h | 48 +++++++++++++++++++++++++++++-- plugins/api.c | 56 ++++++++++++++++++++++++++++++++++++ plugins/qemu-plugins.symbols | 2 ++ 3 files changed, 104 insertions(+), 2 deletions(-) diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h index 93981f8f89f..3b6b18058d2 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -11,6 +11,7 @@ #ifndef QEMU_QEMU_PLUGIN_H #define QEMU_QEMU_PLUGIN_H +#include #include #include #include @@ -229,8 +230,8 @@ struct qemu_plugin_insn; * @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 unused, plugins cannot read or change system - * register state. + * 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, @@ -707,4 +708,47 @@ uint64_t qemu_plugin_end_code(void); QEMU_PLUGIN_API uint64_t qemu_plugin_entry_code(void); +/** struct qemu_plugin_register - Opaque handle for register access */ +struct qemu_plugin_register; + +/** + * typedef qemu_plugin_reg_descriptor - register descriptions + * + * @handle: opaque handle for retrieving value with qemu_plugin_read_register + * @name: register name + * @feature: optional feature descriptor, can be NULL + */ +typedef struct { + struct qemu_plugin_register *handle; + const char *name; + const char *feature; +} qemu_plugin_reg_descriptor; + +/** + * qemu_plugin_get_registers() - return register list for current vCPU + * + * Returns a GArray of qemu_plugin_reg_descriptor or NULL. Caller + * frees the array (but not the const strings). + * + * Should be used from a qemu_plugin_register_vcpu_init_cb() callback + * after the vCPU is initialised, i.e. in the vCPU context. + */ +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 + */ +int qemu_plugin_read_register(struct qemu_plugin_register *handle, + GByteArray *buf); + + #endif /* QEMU_QEMU_PLUGIN_H */ diff --git a/plugins/api.c b/plugins/api.c index 54df72c1c00..03412598047 100644 --- a/plugins/api.c +++ b/plugins/api.c @@ -8,6 +8,7 @@ * * qemu_plugin_tb * qemu_plugin_insn + * qemu_plugin_register * * Which can then be passed back into the API to do additional things. * As such all the public functions in here are exported in @@ -35,10 +36,12 @@ */ #include "qemu/osdep.h" +#include "qemu/main-loop.h" #include "qemu/plugin.h" #include "qemu/log.h" #include "tcg/tcg.h" #include "exec/exec-all.h" +#include "exec/gdbstub.h" #include "exec/ram_addr.h" #include "disas/disas.h" #include "plugin.h" @@ -410,3 +413,56 @@ uint64_t qemu_plugin_entry_code(void) #endif return entry; } + +/* + * Create register handles. + * + * We need to create a handle for each register so the plugin + * infrastructure can call gdbstub to read a register. They are + * currently just a pointer encapsulation of the gdb_regnum but in + * future may hold internal plugin state so its important plugin + * authors are not tempted to treat them as numbers. + * + * We also construct a result array with those handles and some + * ancillary data the plugin might find useful. + */ + +static GArray *create_register_handles(CPUState *cs, GArray *gdbstub_regs) +{ + GArray *find_data = g_array_new(true, true, + sizeof(qemu_plugin_reg_descriptor)); + + for (int i = 0; i < gdbstub_regs->len; i++) { + GDBRegDesc *grd = &g_array_index(gdbstub_regs, GDBRegDesc, i); + + /* skip "un-named" regs */ + if (!grd->name) { + continue; + } + + /* Create a record for the plugin */ + qemu_plugin_reg_descriptor desc = { + .handle = GINT_TO_POINTER(grd->gdb_reg), + .name = g_intern_string(grd->name), + .feature = g_intern_string(grd->feature_name) + }; + g_array_append_val(find_data, desc); + } + + return find_data; +} + +GArray *qemu_plugin_get_registers(void) +{ + g_assert(current_cpu); + + g_autoptr(GArray) regs = gdb_get_register_list(current_cpu); + return regs->len ? create_register_handles(current_cpu, regs) : NULL; +} + +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)); +} diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols index adb67608598..27fe97239be 100644 --- a/plugins/qemu-plugins.symbols +++ b/plugins/qemu-plugins.symbols @@ -3,6 +3,7 @@ qemu_plugin_end_code; qemu_plugin_entry_code; qemu_plugin_get_hwaddr; + qemu_plugin_get_registers; qemu_plugin_hwaddr_device_name; qemu_plugin_hwaddr_is_io; qemu_plugin_hwaddr_phys_addr; @@ -19,6 +20,7 @@ qemu_plugin_num_vcpus; qemu_plugin_outs; qemu_plugin_path_to_binary; + qemu_plugin_read_register; qemu_plugin_register_atexit_cb; qemu_plugin_register_flush_cb; qemu_plugin_register_vcpu_exit_cb;