2 * xdebug.c: Support for emitting gdb debug info for JITted code.
5 * Zoltan Varga (vargaz@gmail.com)
7 * (C) 2010 Novell, Inc.
11 * This works as follows:
12 * - the runtime writes out an xdb.s file containing DWARF debug info.
13 * - the user calls a gdb macro
14 * - the macro compiles and loads this shared library using add-symbol-file.
16 * This is based on the xdebug functionality in the Kaffe Java VM.
18 * We emit assembly code instead of using the ELF writer, so we can emit debug info
19 * incrementally as each method is JITted, and the debugger doesn't have to call
20 * into the runtime to emit the shared library, which would cause all kinds of
21 * complications, like threading issues, and the fact that the ELF writer's
22 * emit_writeout () function cannot be called more than once.
23 * GDB 7.0 and later has a JIT interface.
30 #if !defined(DISABLE_AOT) && !defined(DISABLE_JIT)
31 #include <sys/types.h>
51 #include "image-writer.h"
52 #include "dwarfwriter.h"
54 #define USE_GDB_JIT_INTERFACE
56 /* The recommended gdb macro is: */
59 shell rm -f xdb.so && as --64 -o xdb.o xdb.s && ld -shared -o xdb.so xdb.o
60 add-symbol-file xdb.so 0
65 * GDB JIT interface definitions.
67 * http://sources.redhat.com/gdb/onlinedocs/gdb_30.html
78 struct jit_code_entry *next_entry;
79 struct jit_code_entry *prev_entry;
80 const char *symfile_addr;
87 /* This type should be jit_actions_t, but we use guint32
88 to be explicit about the bitwidth. */
90 struct jit_code_entry *relevant_entry;
91 struct jit_code_entry *first_entry;
96 #define MONO_NOINLINE __declspec (noinline)
98 #define MONO_NOINLINE __attribute__((noinline))
101 /* GDB puts a breakpoint in this function. */
102 void MONO_NOINLINE __jit_debug_register_code(void);
104 #if defined(ENABLE_LLVM) && ((LLVM_MAJOR_VERSION == 2 && LLVM_MINOR_VERSION >= 7) || LLVM_MAJOR_VERSION > 2)
105 /* LLVM already defines these */
106 extern struct jit_descriptor __jit_debug_descriptor;
109 /* Make sure to specify the version statically, because the
110 debugger may check the version before we can set it. */
111 struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
113 void MONO_NOINLINE __jit_debug_register_code(void) { };
116 static MonoImageWriter *xdebug_w;
117 static MonoDwarfWriter *xdebug_writer;
118 static FILE *xdebug_fp, *il_file;
119 static gboolean use_gdb_interface, save_symfiles;
120 static int il_file_line_index;
121 static GHashTable *xdebug_syms;
124 mono_xdebug_init (char *options)
129 args = g_strsplit (options, ",", -1);
130 for (ptr = args; ptr && *ptr; ptr ++) {
133 if (!strcmp (arg, "gdb"))
134 use_gdb_interface = TRUE;
135 if (!strcmp (arg, "save-symfiles"))
136 save_symfiles = TRUE;
139 /* This file will contain the IL code for methods which don't have debug info */
140 il_file = fopen ("xdb.il", "w");
142 if (use_gdb_interface)
146 xdebug_fp = fopen ("xdb.s", "w");
148 w = img_writer_create (xdebug_fp, FALSE);
150 img_writer_emit_start (w);
152 xdebug_writer = mono_dwarf_writer_create (w, il_file, 0, TRUE);
154 /* Emit something so the file has a text segment */
155 img_writer_emit_section_change (w, ".text", 0);
156 img_writer_emit_string (w, "");
158 mono_dwarf_writer_emit_base_info (xdebug_writer, mono_arch_get_cie_program ());
162 xdebug_begin_emit (MonoImageWriter **out_w, MonoDwarfWriter **out_dw)
167 w = img_writer_create (NULL, TRUE);
169 img_writer_emit_start (w);
171 /* This file will contain the IL code for methods which don't have debug info */
173 il_file = fopen ("xdb.il", "w");
175 dw = mono_dwarf_writer_create (w, il_file, il_file_line_index, FALSE);
177 mono_dwarf_writer_emit_base_info (dw, mono_arch_get_cie_program ());
184 xdebug_end_emit (MonoImageWriter *w, MonoDwarfWriter *dw, MonoMethod *method)
188 struct jit_code_entry *entry;
190 il_file_line_index = mono_dwarf_writer_get_il_file_line_index (dw);
191 mono_dwarf_writer_close (dw);
193 img_writer_emit_writeout (w);
195 img = img_writer_get_output (w, &img_size);
197 img_writer_destroy (w);
200 /* Save the symbol files to help debugging */
203 static int file_counter;
206 file_name = g_strdup_printf ("xdb-%d.o", file_counter);
207 //printf ("%s -> %s\n", mono_method_full_name (method, TRUE), file_name);
209 fp = fopen (file_name, "w");
210 fwrite (img, img_size, 1, fp);
215 /* Register the image with GDB */
217 entry = g_malloc (sizeof (struct jit_code_entry));
219 entry->symfile_addr = (const char*)img;
220 entry->symfile_size = img_size;
222 entry->next_entry = __jit_debug_descriptor.first_entry;
223 if (__jit_debug_descriptor.first_entry)
224 __jit_debug_descriptor.first_entry->prev_entry = entry;
225 __jit_debug_descriptor.first_entry = entry;
227 __jit_debug_descriptor.relevant_entry = entry;
228 __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
230 __jit_debug_register_code ();
236 * This could be called from inside gdb to flush the debugging information not yet
237 * registered with gdb.
240 mono_xdebug_flush (void)
243 xdebug_end_emit (xdebug_w, xdebug_writer, NULL);
245 xdebug_begin_emit (&xdebug_w, &xdebug_writer);
248 static int xdebug_method_count;
251 * mono_save_xdebug_info:
253 * Emit debugging info for METHOD into an assembly file which can be assembled
254 * and loaded into gdb to provide debugging info for JITted code.
255 * LOCKING: Acquires the loader lock.
258 mono_save_xdebug_info (MonoCompile *cfg)
260 if (use_gdb_interface) {
264 xdebug_syms = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
267 * gdb is not designed to handle 1000s of symbol files (one per method). So we
268 * group them into groups of 100.
270 if ((xdebug_method_count % 100) == 0)
271 mono_xdebug_flush ();
273 xdebug_method_count ++;
275 mono_dwarf_writer_emit_method (xdebug_writer, cfg, cfg->jit_info->method, NULL, NULL, cfg->jit_info->code_start, cfg->jit_info->code_size, cfg->args, cfg->locals, cfg->unwind_ops, mono_debug_find_method (cfg->jit_info->method, mono_domain_get ()));
279 * Emit a symbol for the code by emitting it at the beginning of the text
280 * segment, and setting the text segment to have an absolute address.
281 * This symbol can be used to set breakpoints in gdb.
282 * FIXME: This doesn't work when multiple methods are emitted into the same file.
284 sym = get_debug_sym (cfg->jit_info->method, "", xdebug_syms);
285 img_writer_emit_section_change (w, ".text", 0);
286 if (!xdebug_text_addr) {
287 xdebug_text_addr = cfg->jit_info->code_start;
288 img_writer_set_section_addr (w, (gssize)xdebug_text_addr);
290 img_writer_emit_global_with_size (w, sym, cfg->jit_info->code_size, TRUE);
291 img_writer_emit_label (w, sym);
292 img_writer_emit_bytes (w, cfg->jit_info->code_start, cfg->jit_info->code_size);
296 mono_loader_unlock ();
302 mono_dwarf_writer_emit_method (xdebug_writer, cfg, cfg->jit_info->method, NULL, NULL, cfg->jit_info->code_start, cfg->jit_info->code_size, cfg->args, cfg->locals, cfg->unwind_ops, mono_debug_find_method (cfg->jit_info->method, mono_domain_get ()));
304 mono_loader_unlock ();
309 * mono_save_trampoline_xdebug_info:
311 * Same as mono_save_xdebug_info, but for trampolines.
312 * LOCKING: Acquires the loader lock.
315 mono_save_trampoline_xdebug_info (const char *tramp_name, guint8 *code, guint32 code_size, GSList *unwind_info)
317 if (use_gdb_interface) {
323 xdebug_begin_emit (&w, &dw);
325 mono_dwarf_writer_emit_trampoline (dw, tramp_name, NULL, NULL, code, code_size, unwind_info);
327 xdebug_end_emit (w, dw, NULL);
329 mono_loader_unlock ();
335 mono_dwarf_writer_emit_trampoline (xdebug_writer, tramp_name, NULL, NULL, code, code_size, unwind_info);
337 mono_loader_unlock ();
341 #else /* !defined(DISABLE_AOT) && !defined(DISABLE_JIT) */
344 mono_xdebug_init (char *options)
349 mono_save_xdebug_info (MonoCompile *cfg)
354 mono_save_trampoline_xdebug_info (const char *tramp_name, guint8 *code, guint32 code_size, GSList *unwind_info)