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, &lmf, 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, MonoLMF **lmf, gboolean *managed)
572 gpointer ip = MONO_CONTEXT_GET_IP (ctx);
574 /* Avoid costly table lookup during stack overflow */
575 if (prev_ji && (ip > prev_ji->code_start && ((guint8*)ip < ((guint8*)prev_ji->code_start) + prev_ji->code_size)))
578 ji = mono_jit_info_table_find (domain, ip);
589 if (!ji->method->wrapper_type)
593 * Some managed methods like pinvoke wrappers might have save_lmf set.
594 * In this case, register save/restore code is not generated by the
595 * JIT, so we have to restore callee saved registers from the lmf.
597 if (ji->method->save_lmf) {
599 * We only need to do this if the exception was raised in managed
600 * code, since otherwise the lmf was already popped of the stack.
602 if (*lmf && (MONO_CONTEXT_GET_BP (ctx) >= (gpointer)(*lmf)->ebp)) {
603 new_ctx->esi = (*lmf)->esi;
604 new_ctx->edi = (*lmf)->edi;
605 new_ctx->ebx = (*lmf)->ebx;
610 /* restore caller saved registers */
611 if (ji->used_regs & X86_EBX_MASK) {
612 new_ctx->ebx = *((int *)ctx->ebp + offset);
615 if (ji->used_regs & X86_EDI_MASK) {
616 new_ctx->edi = *((int *)ctx->ebp + offset);
619 if (ji->used_regs & X86_ESI_MASK) {
620 new_ctx->esi = *((int *)ctx->ebp + offset);
624 if (*lmf && (MONO_CONTEXT_GET_BP (ctx) >= (gpointer)(*lmf)->ebp)) {
625 /* remove any unused lmf */
626 *lmf = (gpointer)(((guint32)(*lmf)->previous_lmf) & ~1);
629 /* Pop EBP and the return address */
630 new_ctx->esp = ctx->ebp + (2 * sizeof (gpointer));
631 /* we substract 1, so that the IP points into the call instruction */
632 new_ctx->eip = *((int *)ctx->ebp + 1) - 1;
633 new_ctx->ebp = *((int *)ctx->ebp);
635 /* Pop arguments off the stack */
637 MonoJitArgumentInfo *arg_info = g_newa (MonoJitArgumentInfo, mono_method_signature (ji->method)->param_count + 1);
639 guint32 stack_to_pop = mono_arch_get_argument_info (mono_method_signature (ji->method), mono_method_signature (ji->method)->param_count, arg_info);
640 new_ctx->esp += stack_to_pop;
648 if ((ji = mono_jit_info_table_find (domain, (gpointer)(*lmf)->eip))) {
653 /* Trampoline lmf frame */
654 memset (res, 0, sizeof (MonoJitInfo));
655 res->method = (*lmf)->method;
658 new_ctx->esi = (*lmf)->esi;
659 new_ctx->edi = (*lmf)->edi;
660 new_ctx->ebx = (*lmf)->ebx;
661 new_ctx->ebp = (*lmf)->ebp;
662 new_ctx->eip = (*lmf)->eip;
664 /* Check if we are in a trampoline LMF frame */
665 if ((guint32)((*lmf)->previous_lmf) & 1) {
666 /* lmf->esp is set by the trampoline code */
667 new_ctx->esp = (*lmf)->esp;
669 /* Pop arguments off the stack */
670 /* FIXME: Handle the delegate case too ((*lmf)->method == NULL) */
671 /* FIXME: Handle the IMT/vtable case too */
672 if ((*lmf)->method && (*lmf)->method != MONO_FAKE_IMT_METHOD && (*lmf)->method != MONO_FAKE_VTABLE_METHOD) {
673 MonoMethod *method = (*lmf)->method;
674 MonoJitArgumentInfo *arg_info = g_newa (MonoJitArgumentInfo, mono_method_signature (method)->param_count + 1);
676 guint32 stack_to_pop = mono_arch_get_argument_info (mono_method_signature (method), mono_method_signature (method)->param_count, arg_info);
677 new_ctx->esp += stack_to_pop;
681 /* the lmf is always stored on the stack, so the following
682 * expression points to a stack location which can be used as ESP */
683 new_ctx->esp = (unsigned long)&((*lmf)->eip);
685 *lmf = (gpointer)(((guint32)(*lmf)->previous_lmf) & ~1);
687 return ji ? ji : res;
706 mono_arch_sigctx_to_monoctx (void *sigctx, MonoContext *mctx)
708 #ifdef MONO_ARCH_USE_SIGACTION
709 ucontext_t *ctx = (ucontext_t*)sigctx;
711 mctx->eax = UCONTEXT_REG_EAX (ctx);
712 mctx->ebx = UCONTEXT_REG_EBX (ctx);
713 mctx->ecx = UCONTEXT_REG_ECX (ctx);
714 mctx->edx = UCONTEXT_REG_EDX (ctx);
715 mctx->ebp = UCONTEXT_REG_EBP (ctx);
716 mctx->esp = UCONTEXT_REG_ESP (ctx);
717 mctx->esi = UCONTEXT_REG_ESI (ctx);
718 mctx->edi = UCONTEXT_REG_EDI (ctx);
719 mctx->eip = UCONTEXT_REG_EIP (ctx);
721 struct sigcontext *ctx = (struct sigcontext *)sigctx;
723 mctx->eax = ctx->SC_EAX;
724 mctx->ebx = ctx->SC_EBX;
725 mctx->ecx = ctx->SC_ECX;
726 mctx->edx = ctx->SC_EDX;
727 mctx->ebp = ctx->SC_EBP;
728 mctx->esp = ctx->SC_ESP;
729 mctx->esi = ctx->SC_ESI;
730 mctx->edi = ctx->SC_EDI;
731 mctx->eip = ctx->SC_EIP;
736 mono_arch_monoctx_to_sigctx (MonoContext *mctx, void *sigctx)
738 #ifdef MONO_ARCH_USE_SIGACTION
739 ucontext_t *ctx = (ucontext_t*)sigctx;
741 UCONTEXT_REG_EAX (ctx) = mctx->eax;
742 UCONTEXT_REG_EBX (ctx) = mctx->ebx;
743 UCONTEXT_REG_ECX (ctx) = mctx->ecx;
744 UCONTEXT_REG_EDX (ctx) = mctx->edx;
745 UCONTEXT_REG_EBP (ctx) = mctx->ebp;
746 UCONTEXT_REG_ESP (ctx) = mctx->esp;
747 UCONTEXT_REG_ESI (ctx) = mctx->esi;
748 UCONTEXT_REG_EDI (ctx) = mctx->edi;
749 UCONTEXT_REG_EIP (ctx) = mctx->eip;
751 struct sigcontext *ctx = (struct sigcontext *)sigctx;
753 ctx->SC_EAX = mctx->eax;
754 ctx->SC_EBX = mctx->ebx;
755 ctx->SC_ECX = mctx->ecx;
756 ctx->SC_EDX = mctx->edx;
757 ctx->SC_EBP = mctx->ebp;
758 ctx->SC_ESP = mctx->esp;
759 ctx->SC_ESI = mctx->esi;
760 ctx->SC_EDI = mctx->edi;
761 ctx->SC_EIP = mctx->eip;
766 mono_arch_ip_from_context (void *sigctx)
768 #ifdef MONO_ARCH_USE_SIGACTION
769 ucontext_t *ctx = (ucontext_t*)sigctx;
770 return (gpointer)UCONTEXT_REG_EIP (ctx);
772 struct sigcontext *ctx = sigctx;
773 return (gpointer)ctx->SC_EIP;
778 mono_arch_handle_exception (void *sigctx, gpointer obj, gboolean test_only)
782 mono_arch_sigctx_to_monoctx (sigctx, &mctx);
784 mono_handle_exception (&mctx, obj, (gpointer)mctx.eip, test_only);
786 mono_arch_monoctx_to_sigctx (&mctx, sigctx);
792 restore_soft_guard_pages (void)
794 MonoJitTlsData *jit_tls = TlsGetValue (mono_jit_tls_id);
795 if (jit_tls->stack_ovf_guard_base)
796 mono_mprotect (jit_tls->stack_ovf_guard_base, jit_tls->stack_ovf_guard_size, MONO_MMAP_NONE);
800 * this function modifies mctx so that when it is restored, it
801 * won't execcute starting at mctx.eip, but in a function that
802 * will restore the protection on the soft-guard pages and return back to
803 * continue at mctx.eip.
806 prepare_for_guard_pages (MonoContext *mctx)
809 sp = (gpointer)(mctx->esp);
811 /* the resturn addr */
812 sp [0] = (gpointer)(mctx->eip);
813 mctx->eip = (unsigned long)restore_soft_guard_pages;
814 mctx->esp = (unsigned long)sp;
818 altstack_handle_and_restore (void *sigctx, gpointer obj, gboolean stack_ovf)
820 void (*restore_context) (MonoContext *);
823 restore_context = mono_arch_get_restore_context ();
824 mono_arch_sigctx_to_monoctx (sigctx, &mctx);
825 mono_handle_exception (&mctx, obj, (gpointer)mctx.eip, FALSE);
827 prepare_for_guard_pages (&mctx);
828 restore_context (&mctx);
832 mono_arch_handle_altstack_exception (void *sigctx, gpointer fault_addr, gboolean stack_ovf)
834 #ifdef MONO_ARCH_USE_SIGACTION
835 MonoException *exc = NULL;
836 ucontext_t *ctx = (ucontext_t*)sigctx;
837 MonoJitInfo *ji = mono_jit_info_table_find (mono_domain_get (), (gpointer)UCONTEXT_REG_EIP (ctx));
841 /* if we didn't find a managed method for the ip address and it matches the fault
842 * address, we assume we followed a broken pointer during an indirect call, so
843 * we try the lookup again with the return address pushed on the stack
845 if (!ji && fault_addr == (gpointer)UCONTEXT_REG_EIP (ctx)) {
846 glong *sp = (gpointer)UCONTEXT_REG_ESP (ctx);
847 ji = mono_jit_info_table_find (mono_domain_get (), (gpointer)sp [0]);
849 UCONTEXT_REG_EIP (ctx) = sp [0];
852 exc = mono_domain_get ()->stack_overflow_ex;
854 mono_handle_native_sigsegv (SIGSEGV, sigctx);
855 /* setup a call frame on the real stack so that control is returned there
856 * and exception handling can continue.
857 * If this was a stack overflow the caller already ensured the stack pages
858 * needed have been unprotected.
859 * The frame looks like:
866 frame_size = sizeof (ucontext_t) + sizeof (gpointer) * 4;
869 sp = (gpointer)(UCONTEXT_REG_ESP (ctx) & ~15);
870 sp = (gpointer)((char*)sp - frame_size);
871 /* the incoming arguments are aligned to 16 bytes boundaries, so the return address IP
874 sp [-1] = (gpointer)UCONTEXT_REG_EIP (ctx);
877 sp [2] = (gpointer)stack_ovf;
878 /* may need to adjust pointers in the new struct copy, depending on the OS */
879 memcpy (sp + 4, ctx, sizeof (ucontext_t));
880 /* at the return form the signal handler execution starts in altstack_handle_and_restore() */
881 UCONTEXT_REG_EIP (ctx) = (unsigned long)altstack_handle_and_restore;
882 UCONTEXT_REG_ESP (ctx) = (unsigned long)(sp - 1);