2 * exceptions-x86.c: exception support for x86
5 * Dietmar Maurer (dietmar@ximian.com)
7 * (C) 2001 Ximian, Inc.
15 #include <mono/arch/x86/x86-codegen.h>
16 #include <mono/metadata/appdomain.h>
17 #include <mono/metadata/tabledefs.h>
18 #include <mono/metadata/threads.h>
19 #include <mono/metadata/debug-helpers.h>
20 #include <mono/metadata/exception.h>
21 #include <mono/metadata/gc-internal.h>
22 #include <mono/metadata/mono-debug.h>
23 #include <mono/utils/mono-mmap.h>
29 static void (*restore_stack) (void *);
31 static MonoW32ExceptionHandler fpe_handler;
32 static MonoW32ExceptionHandler ill_handler;
33 static MonoW32ExceptionHandler segv_handler;
35 static LPTOP_LEVEL_EXCEPTION_FILTER old_handler;
37 #define W32_SEH_HANDLE_EX(_ex) \
38 if (_ex##_handler) _ex##_handler((int)sctx)
41 * mono_win32_get_handle_stackoverflow (void):
43 * Returns a pointer to a method which restores the current context stack
44 * and calls handle_exceptions, when done restores the original stack.
47 mono_win32_get_handle_stackoverflow (void)
49 static guint8 *start = NULL;
55 /* restore_contect (void *sigctx) */
56 start = code = mono_global_codeman_reserve (128);
58 /* load context into ebx */
59 x86_mov_reg_membase (code, X86_EBX, X86_ESP, 4, 4);
61 /* move current stack into edi for later restore */
62 x86_mov_reg_reg (code, X86_EDI, X86_ESP, 4);
64 /* use the new freed stack from sigcontext */
65 x86_mov_reg_membase (code, X86_ESP, X86_EBX, G_STRUCT_OFFSET (struct sigcontext, esp), 4);
67 /* get the current domain */
68 x86_call_code (code, mono_domain_get);
70 /* get stack overflow exception from domain object */
71 x86_mov_reg_membase (code, X86_EAX, X86_EAX, G_STRUCT_OFFSET (MonoDomain, stack_overflow_ex), 4);
73 /* call mono_arch_handle_exception (sctx, stack_overflow_exception_obj, FALSE) */
74 x86_push_imm (code, 0);
75 x86_push_reg (code, X86_EAX);
76 x86_push_reg (code, X86_EBX);
77 x86_call_code (code, mono_arch_handle_exception);
79 /* restore the SEH handler stack */
80 x86_mov_reg_reg (code, X86_ESP, X86_EDI, 4);
88 /* Special hack to workaround the fact that the
89 * when the SEH handler is called the stack is
90 * to small to recover.
92 * Stack walking part of this method is from mono_handle_exception
95 * - walk the stack to free some space (64k)
96 * - set esp to new stack location
97 * - call mono_arch_handle_exception with stack overflow exception
98 * - set esp to SEH handlers stack
102 win32_handle_stack_overflow (EXCEPTION_POINTERS* ep, struct sigcontext *sctx)
106 MonoDomain *domain = mono_domain_get ();
107 MonoJitInfo *ji, rji;
108 MonoJitTlsData *jit_tls = TlsGetValue (mono_jit_tls_id);
109 MonoLMF *lmf = jit_tls->lmf;
110 MonoContext initial_ctx;
112 guint32 free_stack = 0;
114 /* convert sigcontext to MonoContext (due to reuse of stack walking helpers */
115 mono_arch_sigctx_to_monoctx (sctx, &ctx);
117 /* get our os page size */
119 page_size = si.dwPageSize;
121 /* Let's walk the stack to recover
122 * the needed stack space (if possible)
124 memset (&rji, 0, sizeof (rji));
127 free_stack = (guint8*)(MONO_CONTEXT_GET_BP (&ctx)) - (guint8*)(MONO_CONTEXT_GET_BP (&initial_ctx));
129 /* try to free 64kb from our stack */
133 ji = mono_arch_find_jit_info (domain, jit_tls, &rji, &rji, &ctx, &new_ctx, NULL, &lmf, NULL, NULL);
135 g_warning ("Exception inside function without unwind info");
136 g_assert_not_reached ();
139 if (ji != (gpointer)-1) {
140 free_stack = (guint8*)(MONO_CONTEXT_GET_BP (&ctx)) - (guint8*)(MONO_CONTEXT_GET_BP (&initial_ctx));
143 /* todo: we should call abort if ji is -1 */
145 } while (free_stack < 64 * 1024 && ji != (gpointer) -1);
147 /* convert into sigcontext to be used in mono_arch_handle_exception */
148 mono_arch_monoctx_to_sigctx (&ctx, sctx);
150 /* todo: install new stack-guard page */
152 /* use the new stack and call mono_arch_handle_exception () */
153 restore_stack (sctx);
157 * Unhandled Exception Filter
158 * Top-level per-process exception handler.
160 LONG CALLBACK seh_handler(EXCEPTION_POINTERS* ep)
162 EXCEPTION_RECORD* er;
164 struct sigcontext* sctx;
167 res = EXCEPTION_CONTINUE_EXECUTION;
169 er = ep->ExceptionRecord;
170 ctx = ep->ContextRecord;
171 sctx = g_malloc(sizeof(struct sigcontext));
173 /* Copy Win32 context to UNIX style context */
174 sctx->eax = ctx->Eax;
175 sctx->ebx = ctx->Ebx;
176 sctx->ecx = ctx->Ecx;
177 sctx->edx = ctx->Edx;
178 sctx->ebp = ctx->Ebp;
179 sctx->esp = ctx->Esp;
180 sctx->esi = ctx->Esi;
181 sctx->edi = ctx->Edi;
182 sctx->eip = ctx->Eip;
184 switch (er->ExceptionCode) {
185 case EXCEPTION_STACK_OVERFLOW:
186 win32_handle_stack_overflow (ep, sctx);
188 case EXCEPTION_ACCESS_VIOLATION:
189 W32_SEH_HANDLE_EX(segv);
191 case EXCEPTION_ILLEGAL_INSTRUCTION:
192 W32_SEH_HANDLE_EX(ill);
194 case EXCEPTION_INT_DIVIDE_BY_ZERO:
195 case EXCEPTION_INT_OVERFLOW:
196 case EXCEPTION_FLT_DIVIDE_BY_ZERO:
197 case EXCEPTION_FLT_OVERFLOW:
198 case EXCEPTION_FLT_UNDERFLOW:
199 case EXCEPTION_FLT_INEXACT_RESULT:
200 W32_SEH_HANDLE_EX(fpe);
206 /* Copy context back */
207 ctx->Eax = sctx->eax;
208 ctx->Ebx = sctx->ebx;
209 ctx->Ecx = sctx->ecx;
210 ctx->Edx = sctx->edx;
211 ctx->Ebp = sctx->ebp;
212 ctx->Esp = sctx->esp;
213 ctx->Esi = sctx->esi;
214 ctx->Edi = sctx->edi;
215 ctx->Eip = sctx->eip;
222 void win32_seh_init()
224 /* install restore stack helper */
226 restore_stack = mono_win32_get_handle_stackoverflow ();
228 old_handler = SetUnhandledExceptionFilter(seh_handler);
231 void win32_seh_cleanup()
233 if (old_handler) SetUnhandledExceptionFilter(old_handler);
236 void win32_seh_set_handler(int type, MonoW32ExceptionHandler handler)
240 fpe_handler = handler;
243 ill_handler = handler;
246 segv_handler = handler;
253 #endif /* PLATFORM_WIN32 */
256 * mono_arch_get_restore_context:
258 * Returns a pointer to a method which restores a previously saved sigcontext.
261 mono_arch_get_restore_context (void)
263 static guint8 *start = NULL;
269 /* restore_contect (MonoContext *ctx) */
270 /* we do not restore X86_EAX, X86_EDX */
272 start = code = mono_global_codeman_reserve (128);
275 x86_mov_reg_membase (code, X86_EAX, X86_ESP, 4, 4);
277 /* get return address, stored in EDX */
278 x86_mov_reg_membase (code, X86_EDX, X86_EAX, G_STRUCT_OFFSET (MonoContext, eip), 4);
280 x86_mov_reg_membase (code, X86_EBX, X86_EAX, G_STRUCT_OFFSET (MonoContext, ebx), 4);
282 x86_mov_reg_membase (code, X86_EDI, X86_EAX, G_STRUCT_OFFSET (MonoContext, edi), 4);
284 x86_mov_reg_membase (code, X86_ESI, X86_EAX, G_STRUCT_OFFSET (MonoContext, esi), 4);
286 x86_mov_reg_membase (code, X86_ESP, X86_EAX, G_STRUCT_OFFSET (MonoContext, esp), 4);
288 x86_mov_reg_membase (code, X86_EBP, X86_EAX, G_STRUCT_OFFSET (MonoContext, ebp), 4);
290 /* jump to the saved IP */
291 x86_jump_reg (code, X86_EDX);
297 * mono_arch_get_call_filter:
299 * Returns a pointer to a method which calls an exception filter. We
300 * also use this function to call finally handlers (we pass NULL as
301 * @exc object in this case).
304 mono_arch_get_call_filter (void)
306 static guint8* start;
307 static int inited = 0;
314 /* call_filter (MonoContext *ctx, unsigned long eip) */
315 start = code = mono_global_codeman_reserve (64);
317 x86_push_reg (code, X86_EBP);
318 x86_mov_reg_reg (code, X86_EBP, X86_ESP, 4);
319 x86_push_reg (code, X86_EBX);
320 x86_push_reg (code, X86_EDI);
321 x86_push_reg (code, X86_ESI);
324 x86_mov_reg_membase (code, X86_EAX, X86_EBP, 8, 4);
326 x86_mov_reg_membase (code, X86_ECX, X86_EBP, 12, 4);
328 x86_push_reg (code, X86_EBP);
331 x86_mov_reg_membase (code, X86_EBP, X86_EAX, G_STRUCT_OFFSET (MonoContext, ebp), 4);
332 /* restore registers used by global register allocation (EBX & ESI) */
333 x86_mov_reg_membase (code, X86_EBX, X86_EAX, G_STRUCT_OFFSET (MonoContext, ebx), 4);
334 x86_mov_reg_membase (code, X86_ESI, X86_EAX, G_STRUCT_OFFSET (MonoContext, esi), 4);
335 x86_mov_reg_membase (code, X86_EDI, X86_EAX, G_STRUCT_OFFSET (MonoContext, edi), 4);
337 /* call the handler */
338 x86_call_reg (code, X86_ECX);
341 x86_pop_reg (code, X86_EBP);
343 /* restore saved regs */
344 x86_pop_reg (code, X86_ESI);
345 x86_pop_reg (code, X86_EDI);
346 x86_pop_reg (code, X86_EBX);
350 g_assert ((code - start) < 64);
355 throw_exception (unsigned long eax, unsigned long ecx, unsigned long edx, unsigned long ebx,
356 unsigned long esi, unsigned long edi, unsigned long ebp, MonoObject *exc,
357 unsigned long eip, unsigned long esp, gboolean rethrow)
359 static void (*restore_context) (MonoContext *);
362 if (!restore_context)
363 restore_context = mono_arch_get_restore_context ();
365 /* Pop argument and return address */
366 ctx.esp = esp + (2 * sizeof (gpointer));
376 if (mono_debugger_throw_exception ((gpointer)(eip - 5), (gpointer)esp, exc)) {
378 * The debugger wants us to stop on the `throw' instruction.
379 * By the time we get here, it already inserted a breakpoint on
380 * eip - 5 (which is the address of the call).
383 ctx.esp = esp + sizeof (gpointer);
384 restore_context (&ctx);
385 g_assert_not_reached ();
388 /* adjust eip so that it point into the call instruction */
391 if (mono_object_isinst (exc, mono_defaults.exception_class)) {
392 MonoException *mono_ex = (MonoException*)exc;
394 mono_ex->stack_trace = NULL;
396 mono_handle_exception (&ctx, exc, (gpointer)eip, FALSE);
397 restore_context (&ctx);
399 g_assert_not_reached ();
403 get_throw_exception (gboolean rethrow)
405 guint8 *start, *code;
407 start = code = mono_global_codeman_reserve (64);
409 x86_push_reg (code, X86_ESP);
410 x86_push_membase (code, X86_ESP, 4); /* IP */
411 x86_push_membase (code, X86_ESP, 12); /* exception */
412 x86_push_reg (code, X86_EBP);
413 x86_push_reg (code, X86_EDI);
414 x86_push_reg (code, X86_ESI);
415 x86_push_reg (code, X86_EBX);
416 x86_push_reg (code, X86_EDX);
417 x86_push_reg (code, X86_ECX);
418 x86_push_reg (code, X86_EAX);
419 x86_call_code (code, throw_exception);
420 /* we should never reach this breakpoint */
421 x86_breakpoint (code);
423 g_assert ((code - start) < 64);
429 * mono_arch_get_throw_exception:
431 * Returns a function pointer which can be used to raise
432 * exceptions. The returned function has the following
433 * signature: void (*func) (MonoException *exc);
434 * For example to raise an arithmetic exception you can use:
436 * x86_push_imm (code, mono_get_exception_arithmetic ());
437 * x86_call_code (code, arch_get_throw_exception ());
441 mono_arch_get_throw_exception (void)
443 static guint8 *start;
444 static int inited = 0;
449 start = get_throw_exception (FALSE);
457 mono_arch_get_rethrow_exception (void)
459 static guint8 *start;
460 static int inited = 0;
465 start = get_throw_exception (TRUE);
473 * mono_arch_get_throw_exception_by_name:
475 * Returns a function pointer which can be used to raise
476 * corlib exceptions. The returned function has the following
477 * signature: void (*func) (gpointer ip, char *exc_name);
478 * For example to raise an arithmetic exception you can use:
480 * x86_push_imm (code, "ArithmeticException");
481 * x86_push_imm (code, <IP>)
482 * x86_jump_code (code, arch_get_throw_exception_by_name ());
486 mono_arch_get_throw_exception_by_name (void)
488 static guint8* start;
489 static int inited = 0;
496 code = start = mono_global_codeman_reserve (32);
498 x86_push_membase (code, X86_ESP, 4); /* exception name */
499 x86_push_imm (code, "System");
500 x86_push_imm (code, mono_defaults.exception_class->image);
501 x86_call_code (code, mono_exception_from_name);
502 x86_alu_reg_imm (code, X86_ADD, X86_ESP, 12);
503 /* save the newly create object (overwrite exception name)*/
504 x86_mov_membase_reg (code, X86_ESP, 4, X86_EAX, 4);
505 x86_jump_code (code, mono_arch_get_throw_exception ());
507 g_assert ((code - start) < 32);
513 * mono_arch_get_throw_corlib_exception:
515 * Returns a function pointer which can be used to raise
516 * corlib exceptions. The returned function has the following
517 * signature: void (*func) (guint32 ex_token, guint32 offset);
518 * Here, offset is the offset which needs to be substracted from the caller IP
519 * to get the IP of the throw. Passing the offset has the advantage that it
520 * needs no relocations in the caller.
523 mono_arch_get_throw_corlib_exception (void)
525 static guint8* start;
526 static int inited = 0;
533 code = start = mono_global_codeman_reserve (64);
535 x86_mov_reg_membase (code, X86_EAX, X86_ESP, 4, 4); /* token */
536 x86_alu_reg_imm (code, X86_ADD, X86_EAX, MONO_TOKEN_TYPE_DEF);
537 x86_push_reg (code, X86_EAX);
538 x86_push_imm (code, mono_defaults.exception_class->image);
539 x86_call_code (code, mono_exception_from_token);
540 x86_alu_reg_imm (code, X86_ADD, X86_ESP, 8);
541 /* Compute caller ip */
542 x86_pop_reg (code, X86_ECX);
544 x86_alu_reg_imm (code, X86_ADD, X86_ESP, 4);
545 x86_pop_reg (code, X86_EDX);
546 x86_alu_reg_reg (code, X86_SUB, X86_ECX, X86_EDX);
547 /* Push exception object */
548 x86_push_reg (code, X86_EAX);
550 x86_push_reg (code, X86_ECX);
551 x86_jump_code (code, mono_arch_get_throw_exception ());
553 g_assert ((code - start) < 64);
558 /* mono_arch_find_jit_info:
560 * This function is used to gather information from @ctx. It return the
561 * MonoJitInfo of the corresponding function, unwinds one stack frame and
562 * stores the resulting context into @new_ctx. It also stores a string
563 * describing the stack location into @trace (if not NULL), and modifies
564 * the @lmf if necessary. @native_offset return the IP offset from the
565 * start of the function or -1 if that info is not available.
568 mono_arch_find_jit_info (MonoDomain *domain, MonoJitTlsData *jit_tls, MonoJitInfo *res, MonoJitInfo *prev_ji, MonoContext *ctx,
569 MonoContext *new_ctx, char **trace, MonoLMF **lmf, int *native_offset,
573 gpointer ip = MONO_CONTEXT_GET_IP (ctx);
575 /* Avoid costly table lookup during stack overflow */
576 if (prev_ji && (ip > prev_ji->code_start && ((guint8*)ip < ((guint8*)prev_ji->code_start) + prev_ji->code_size)))
579 ji = mono_jit_info_table_find (domain, ip);
590 if (!ji->method->wrapper_type)
594 * Some managed methods like pinvoke wrappers might have save_lmf set.
595 * In this case, register save/restore code is not generated by the
596 * JIT, so we have to restore callee saved registers from the lmf.
598 if (ji->method->save_lmf) {
600 * We only need to do this if the exception was raised in managed
601 * code, since otherwise the lmf was already popped of the stack.
603 if (*lmf && (MONO_CONTEXT_GET_BP (ctx) >= (gpointer)(*lmf)->ebp)) {
604 new_ctx->esi = (*lmf)->esi;
605 new_ctx->edi = (*lmf)->edi;
606 new_ctx->ebx = (*lmf)->ebx;
611 /* restore caller saved registers */
612 if (ji->used_regs & X86_EBX_MASK) {
613 new_ctx->ebx = *((int *)ctx->ebp + offset);
616 if (ji->used_regs & X86_EDI_MASK) {
617 new_ctx->edi = *((int *)ctx->ebp + offset);
620 if (ji->used_regs & X86_ESI_MASK) {
621 new_ctx->esi = *((int *)ctx->ebp + offset);
625 if (*lmf && (MONO_CONTEXT_GET_BP (ctx) >= (gpointer)(*lmf)->ebp)) {
626 /* remove any unused lmf */
627 *lmf = (gpointer)(((guint32)(*lmf)->previous_lmf) & ~1);
630 /* Pop EBP and the return address */
631 new_ctx->esp = ctx->ebp + (2 * sizeof (gpointer));
632 /* we substract 1, so that the IP points into the call instruction */
633 new_ctx->eip = *((int *)ctx->ebp + 1) - 1;
634 new_ctx->ebp = *((int *)ctx->ebp);
636 /* Pop arguments off the stack */
638 MonoJitArgumentInfo *arg_info = g_newa (MonoJitArgumentInfo, mono_method_signature (ji->method)->param_count + 1);
640 guint32 stack_to_pop = mono_arch_get_argument_info (mono_method_signature (ji->method), mono_method_signature (ji->method)->param_count, arg_info);
641 new_ctx->esp += stack_to_pop;
649 if ((ji = mono_jit_info_table_find (domain, (gpointer)(*lmf)->eip))) {
654 /* Trampoline lmf frame */
655 memset (res, 0, sizeof (MonoJitInfo));
656 res->method = (*lmf)->method;
659 new_ctx->esi = (*lmf)->esi;
660 new_ctx->edi = (*lmf)->edi;
661 new_ctx->ebx = (*lmf)->ebx;
662 new_ctx->ebp = (*lmf)->ebp;
663 new_ctx->eip = (*lmf)->eip;
665 /* Check if we are in a trampoline LMF frame */
666 if ((guint32)((*lmf)->previous_lmf) & 1) {
667 /* lmf->esp is set by the trampoline code */
668 new_ctx->esp = (*lmf)->esp;
670 /* Pop arguments off the stack */
671 /* FIXME: Handle the delegate case too ((*lmf)->method == NULL) */
672 /* FIXME: Handle the IMT/vtable case too */
673 if ((*lmf)->method && (*lmf)->method != MONO_FAKE_IMT_METHOD && (*lmf)->method != MONO_FAKE_VTABLE_METHOD) {
674 MonoMethod *method = (*lmf)->method;
675 MonoJitArgumentInfo *arg_info = g_newa (MonoJitArgumentInfo, mono_method_signature (method)->param_count + 1);
677 guint32 stack_to_pop = mono_arch_get_argument_info (mono_method_signature (method), mono_method_signature (method)->param_count, arg_info);
678 new_ctx->esp += stack_to_pop;
682 /* the lmf is always stored on the stack, so the following
683 * expression points to a stack location which can be used as ESP */
684 new_ctx->esp = (unsigned long)&((*lmf)->eip);
686 *lmf = (gpointer)(((guint32)(*lmf)->previous_lmf) & ~1);
688 return ji ? ji : res;
707 mono_arch_sigctx_to_monoctx (void *sigctx, MonoContext *mctx)
709 #ifdef MONO_ARCH_USE_SIGACTION
710 ucontext_t *ctx = (ucontext_t*)sigctx;
712 mctx->eax = UCONTEXT_REG_EAX (ctx);
713 mctx->ebx = UCONTEXT_REG_EBX (ctx);
714 mctx->ecx = UCONTEXT_REG_ECX (ctx);
715 mctx->edx = UCONTEXT_REG_EDX (ctx);
716 mctx->ebp = UCONTEXT_REG_EBP (ctx);
717 mctx->esp = UCONTEXT_REG_ESP (ctx);
718 mctx->esi = UCONTEXT_REG_ESI (ctx);
719 mctx->edi = UCONTEXT_REG_EDI (ctx);
720 mctx->eip = UCONTEXT_REG_EIP (ctx);
722 struct sigcontext *ctx = (struct sigcontext *)sigctx;
724 mctx->eax = ctx->SC_EAX;
725 mctx->ebx = ctx->SC_EBX;
726 mctx->ecx = ctx->SC_ECX;
727 mctx->edx = ctx->SC_EDX;
728 mctx->ebp = ctx->SC_EBP;
729 mctx->esp = ctx->SC_ESP;
730 mctx->esi = ctx->SC_ESI;
731 mctx->edi = ctx->SC_EDI;
732 mctx->eip = ctx->SC_EIP;
737 mono_arch_monoctx_to_sigctx (MonoContext *mctx, void *sigctx)
739 #ifdef MONO_ARCH_USE_SIGACTION
740 ucontext_t *ctx = (ucontext_t*)sigctx;
742 UCONTEXT_REG_EAX (ctx) = mctx->eax;
743 UCONTEXT_REG_EBX (ctx) = mctx->ebx;
744 UCONTEXT_REG_ECX (ctx) = mctx->ecx;
745 UCONTEXT_REG_EDX (ctx) = mctx->edx;
746 UCONTEXT_REG_EBP (ctx) = mctx->ebp;
747 UCONTEXT_REG_ESP (ctx) = mctx->esp;
748 UCONTEXT_REG_ESI (ctx) = mctx->esi;
749 UCONTEXT_REG_EDI (ctx) = mctx->edi;
750 UCONTEXT_REG_EIP (ctx) = mctx->eip;
752 struct sigcontext *ctx = (struct sigcontext *)sigctx;
754 ctx->SC_EAX = mctx->eax;
755 ctx->SC_EBX = mctx->ebx;
756 ctx->SC_ECX = mctx->ecx;
757 ctx->SC_EDX = mctx->edx;
758 ctx->SC_EBP = mctx->ebp;
759 ctx->SC_ESP = mctx->esp;
760 ctx->SC_ESI = mctx->esi;
761 ctx->SC_EDI = mctx->edi;
762 ctx->SC_EIP = mctx->eip;
767 mono_arch_ip_from_context (void *sigctx)
769 #ifdef MONO_ARCH_USE_SIGACTION
770 ucontext_t *ctx = (ucontext_t*)sigctx;
771 return (gpointer)UCONTEXT_REG_EIP (ctx);
773 struct sigcontext *ctx = sigctx;
774 return (gpointer)ctx->SC_EIP;
779 mono_arch_handle_exception (void *sigctx, gpointer obj, gboolean test_only)
783 mono_arch_sigctx_to_monoctx (sigctx, &mctx);
785 mono_handle_exception (&mctx, obj, (gpointer)mctx.eip, test_only);
787 mono_arch_monoctx_to_sigctx (&mctx, sigctx);
793 restore_soft_guard_pages (void)
795 MonoJitTlsData *jit_tls = TlsGetValue (mono_jit_tls_id);
796 if (jit_tls->stack_ovf_guard_base)
797 mono_mprotect (jit_tls->stack_ovf_guard_base, jit_tls->stack_ovf_guard_size, MONO_MMAP_NONE);
801 * this function modifies mctx so that when it is restored, it
802 * won't execcute starting at mctx.eip, but in a function that
803 * will restore the protection on the soft-guard pages and return back to
804 * continue at mctx.eip.
807 prepare_for_guard_pages (MonoContext *mctx)
810 sp = (gpointer)(mctx->esp);
812 /* the resturn addr */
813 sp [0] = (gpointer)(mctx->eip);
814 mctx->eip = (unsigned long)restore_soft_guard_pages;
815 mctx->esp = (unsigned long)sp;
819 altstack_handle_and_restore (void *sigctx, gpointer obj, gboolean stack_ovf)
821 void (*restore_context) (MonoContext *);
824 restore_context = mono_arch_get_restore_context ();
825 mono_arch_sigctx_to_monoctx (sigctx, &mctx);
826 mono_handle_exception (&mctx, obj, (gpointer)mctx.eip, FALSE);
828 prepare_for_guard_pages (&mctx);
829 restore_context (&mctx);
833 mono_arch_handle_altstack_exception (void *sigctx, gpointer fault_addr, gboolean stack_ovf)
835 #ifdef MONO_ARCH_USE_SIGACTION
836 MonoException *exc = NULL;
837 ucontext_t *ctx = (ucontext_t*)sigctx;
838 MonoJitInfo *ji = mono_jit_info_table_find (mono_domain_get (), (gpointer)UCONTEXT_REG_EIP (ctx));
842 /* if we didn't find a managed method for the ip address and it matches the fault
843 * address, we assume we followed a broken pointer during an indirect call, so
844 * we try the lookup again with the return address pushed on the stack
846 if (!ji && fault_addr == (gpointer)UCONTEXT_REG_EIP (ctx)) {
847 glong *sp = (gpointer)UCONTEXT_REG_ESP (ctx);
848 ji = mono_jit_info_table_find (mono_domain_get (), (gpointer)sp [0]);
850 UCONTEXT_REG_EIP (ctx) = sp [0];
853 exc = mono_domain_get ()->stack_overflow_ex;
855 mono_handle_native_sigsegv (SIGSEGV, sigctx);
856 /* setup a call frame on the real stack so that control is returned there
857 * and exception handling can continue.
858 * If this was a stack overflow the caller already ensured the stack pages
859 * needed have been unprotected.
860 * The frame looks like:
867 frame_size = sizeof (ucontext_t) + sizeof (gpointer) * 4;
870 sp = (gpointer)(UCONTEXT_REG_ESP (ctx) & ~15);
871 sp = (gpointer)((char*)sp - frame_size);
872 /* the incoming arguments are aligned to 16 bytes boundaries, so the return address IP
875 sp [-1] = (gpointer)UCONTEXT_REG_EIP (ctx);
878 sp [2] = (gpointer)stack_ovf;
879 /* may need to adjust pointers in the new struct copy, depending on the OS */
880 memcpy (sp + 4, ctx, sizeof (ucontext_t));
881 /* at the return form the signal handler execution starts in altstack_handle_and_restore() */
882 UCONTEXT_REG_EIP (ctx) = (unsigned long)altstack_handle_and_restore;
883 UCONTEXT_REG_ESP (ctx) = (unsigned long)(sp - 1);