unwind trace

Author: pbo-linaro

include/qemu/osdep.h

@@ -133,6 +133,9 @@ QEMU_EXTERN_C int daemon(int, int);
 #include <setjmp.h>
 #include <signal.h>
 
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+
 #ifdef CONFIG_IOVEC
 #include <sys/uio.h>
 #endif
@@ -812,6 +815,44 @@ static inline void qemu_thread_jit_write(void) {}
 static inline void qemu_thread_jit_execute(void) {}
 #endif
 
+/* returns caller, return 0 if it worked */
+static inline __attribute__((always_inline))
+int unwind_caller(GString *res)
+{
+    unw_cursor_t cursor;
+    unw_context_t context;
+
+    unw_getcontext(&context);
+    unw_init_local(&cursor, &context);
+
+    bool unwind_success = unw_step(&cursor);
+    if (!unwind_success) {
+        g_string_printf(res, "<unknown - can't unwind>");
+        return -1;
+    }
+
+    unw_word_t offset;
+    char sym[256];
+    if (unw_get_proc_name(&cursor, sym, sizeof(sym), &offset) != 0) {
+        g_string_printf(res, "<unknown - can't get proc info>");
+        return -2;
+    }
+
+    g_string_printf(res, "%s+0x%"PRIx64, sym, offset);
+    return 0;
+}
+
+static inline __attribute__((always_inline))
+const char* qemu_get_caller(void)
+{
+    static __thread GString *info;
+    if (!info) {
+        info = g_string_new(0);
+    }
+    unwind_caller(info);
+    return info->str;
+}
+
 /**
  * Platforms which do not support system() return ENOSYS
  */

meson.build

@@ -954,6 +954,9 @@ have_xen_pci_passthrough = get_option('xen_pci_passthrough') \
 # Dependencies #
 ################
 
+libunwind = dependency('libunwind', required: true, method: 'pkg-config')
+add_project_dependencies(libunwind, language: all_languages)
+
 # When bumping glib minimum version, please check also whether to increase
 # the _WIN32_WINNT setting in osdep.h according to the value from glib.
 # You should also check if any of the glib.version() checks
@@ -3577,6 +3580,7 @@ event_loop_base = declare_dependency(objects: event_loop_base.extract_all_object
 stub_ss = stub_ss.apply({})
 
 util_ss.add_all(trace_ss)
+util_ss.add(libunwind)
 util_ss = util_ss.apply({})
 libqemuutil = static_library('qemuutil',
                              build_by_default: false,