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;
82 * The gdb code in gdb/jit.c which reads this structure ignores alignment
83 * requirements, so use two 32 bit fields.
85 guint32 symfile_size1, symfile_size2;
91 /* This type should be jit_actions_t, but we use guint32
92 to be explicit about the bitwidth. */
94 struct jit_code_entry *relevant_entry;
95 struct jit_code_entry *first_entry;
100 #define MONO_NOINLINE __declspec (noinline)
102 #define MONO_NOINLINE __attribute__((noinline))
105 /* GDB puts a breakpoint in this function. */
106 void MONO_NOINLINE __jit_debug_register_code(void);
108 #if !defined(MONO_LLVM_LOADED) && defined(ENABLE_LLVM) && ((LLVM_MAJOR_VERSION == 2 && LLVM_MINOR_VERSION >= 7) || LLVM_MAJOR_VERSION > 2)
110 /* LLVM already defines these */
111 extern struct jit_descriptor __jit_debug_descriptor;
115 /* Make sure to specify the version statically, because the
116 debugger may check the version before we can set it. */
117 struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
119 /* gcc seems to inline/eliminate calls to noinline functions, thus the asm () */
120 void MONO_NOINLINE __jit_debug_register_code(void) {
121 #if defined(__GNUC__)
128 static MonoImageWriter *xdebug_w;
129 static MonoDwarfWriter *xdebug_writer;
130 static FILE *xdebug_fp, *il_file;
131 static gboolean use_gdb_interface, save_symfiles;
132 static int il_file_line_index;
133 static GHashTable *xdebug_syms;
136 mono_xdebug_init (char *options)
141 args = g_strsplit (options, ",", -1);
142 for (ptr = args; ptr && *ptr; ptr ++) {
145 if (!strcmp (arg, "gdb"))
146 use_gdb_interface = TRUE;
147 if (!strcmp (arg, "save-symfiles"))
148 save_symfiles = TRUE;
151 /* This file will contain the IL code for methods which don't have debug info */
152 il_file = fopen ("xdb.il", "w");
153 if (il_file == NULL) {
154 use_gdb_interface = FALSE;
155 g_warning ("** Unable to create xdb.il. Managed symbol names won't be available.");
159 if (use_gdb_interface)
163 xdebug_fp = fopen ("xdb.s", "w");
165 w = img_writer_create (xdebug_fp, FALSE);
167 img_writer_emit_start (w);
169 xdebug_writer = mono_dwarf_writer_create (w, il_file, 0, TRUE);
171 /* Emit something so the file has a text segment */
172 img_writer_emit_section_change (w, ".text", 0);
173 img_writer_emit_string (w, "");
175 mono_dwarf_writer_emit_base_info (xdebug_writer, mono_unwind_get_cie_program ());
179 xdebug_begin_emit (MonoImageWriter **out_w, MonoDwarfWriter **out_dw)
184 w = img_writer_create (NULL, TRUE);
186 img_writer_emit_start (w);
188 /* This file will contain the IL code for methods which don't have debug info */
190 il_file = fopen ("xdb.il", "w");
192 dw = mono_dwarf_writer_create (w, il_file, il_file_line_index, FALSE);
194 mono_dwarf_writer_emit_base_info (dw, mono_unwind_get_cie_program ());
201 xdebug_end_emit (MonoImageWriter *w, MonoDwarfWriter *dw, MonoMethod *method)
205 struct jit_code_entry *entry;
208 il_file_line_index = mono_dwarf_writer_get_il_file_line_index (dw);
209 mono_dwarf_writer_close (dw);
211 img_writer_emit_writeout (w);
213 img = img_writer_get_output (w, &img_size);
215 img_writer_destroy (w);
218 /* Save the symbol files to help debugging */
221 static int file_counter;
224 file_name = g_strdup_printf ("xdb-%d.o", file_counter);
225 printf ("%s %p %d\n", file_name, img, img_size);
227 fp = fopen (file_name, "w");
228 fwrite (img, img_size, 1, fp);
233 /* Register the image with GDB */
235 entry = g_malloc0 (sizeof (struct jit_code_entry));
237 entry->symfile_addr = (const char*)img;
238 psize = (guint64*)&entry->symfile_size1;
241 entry->next_entry = __jit_debug_descriptor.first_entry;
242 if (__jit_debug_descriptor.first_entry)
243 __jit_debug_descriptor.first_entry->prev_entry = entry;
244 __jit_debug_descriptor.first_entry = entry;
246 __jit_debug_descriptor.relevant_entry = entry;
247 __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
249 __jit_debug_register_code ();
255 * This could be called from inside gdb to flush the debugging information not yet
256 * registered with gdb.
259 mono_xdebug_flush (void)
262 xdebug_end_emit (xdebug_w, xdebug_writer, NULL);
264 xdebug_begin_emit (&xdebug_w, &xdebug_writer);
267 static int xdebug_method_count;
270 * mono_save_xdebug_info:
272 * Emit debugging info for METHOD into an assembly file which can be assembled
273 * and loaded into gdb to provide debugging info for JITted code.
274 * LOCKING: Acquires the loader lock.
277 mono_save_xdebug_info (MonoCompile *cfg)
279 MonoDebugMethodJitInfo *dmji;
281 if (use_gdb_interface) {
285 xdebug_syms = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
288 * gdb is not designed to handle 1000s of symbol files (one per method). So we
289 * group them into groups of 100.
291 if ((xdebug_method_count % 100) == 0)
292 mono_xdebug_flush ();
294 xdebug_method_count ++;
296 dmji = mono_debug_find_method (cfg->jit_info->method, mono_domain_get ());;
297 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, dmji);
298 mono_debug_free_method_jit_info (dmji);
302 * Emit a symbol for the code by emitting it at the beginning of the text
303 * segment, and setting the text segment to have an absolute address.
304 * This symbol can be used to set breakpoints in gdb.
305 * FIXME: This doesn't work when multiple methods are emitted into the same file.
307 sym = get_debug_sym (cfg->jit_info->method, "", xdebug_syms);
308 img_writer_emit_section_change (w, ".text", 0);
309 if (!xdebug_text_addr) {
310 xdebug_text_addr = cfg->jit_info->code_start;
311 img_writer_set_section_addr (w, (gssize)xdebug_text_addr);
313 img_writer_emit_global_with_size (w, sym, cfg->jit_info->code_size, TRUE);
314 img_writer_emit_label (w, sym);
315 img_writer_emit_bytes (w, cfg->jit_info->code_start, cfg->jit_info->code_size);
319 mono_loader_unlock ();
325 dmji = mono_debug_find_method (cfg->jit_info->method, mono_domain_get ());;
326 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, dmji);
327 mono_debug_free_method_jit_info (dmji);
329 mono_loader_unlock ();
335 * mono_save_trampoline_xdebug_info:
337 * Same as mono_save_xdebug_info, but for trampolines.
338 * LOCKING: Acquires the loader lock.
341 mono_save_trampoline_xdebug_info (MonoTrampInfo *info)
343 if (use_gdb_interface) {
347 /* This can be called before the loader lock is initialized */
348 mono_loader_lock_if_inited ();
350 xdebug_begin_emit (&w, &dw);
352 mono_dwarf_writer_emit_trampoline (dw, info->name, NULL, NULL, info->code, info->code_size, info->unwind_ops);
354 xdebug_end_emit (w, dw, NULL);
356 mono_loader_unlock_if_inited ();
361 mono_loader_lock_if_inited ();
362 mono_dwarf_writer_emit_trampoline (xdebug_writer, info->name, NULL, NULL, info->code, info->code_size, info->unwind_ops);
364 mono_loader_unlock_if_inited ();
368 #else /* !defined(DISABLE_AOT) && !defined(DISABLE_JIT) */
371 mono_xdebug_init (char *options)
376 mono_save_xdebug_info (MonoCompile *cfg)
381 mono_save_trampoline_xdebug_info (MonoTrampInfo *info)