Support for backtracing exceptions

conf/i386.rmk

@@ -25,3 +25,9 @@ pkglib_MODULES += ata.mod
 ata_mod_SOURCES = disk/ata.c
 ata_mod_CFLAGS = $(COMMON_CFLAGS)
 ata_mod_LDFLAGS = $(COMMON_LDFLAGS)
+
+pkglib_MODULES += backtrace.mod
+backtrace_mod_SOURCES = lib/i386/backtrace.c lib/i386/backtrace_int.S
+backtrace_mod_CFLAGS = $(COMMON_CFLAGS)
+backtrace_mod_ASFLAGS = $(COMMON_ASFLAGS)
+backtrace_mod_LDFLAGS = $(COMMON_LDFLAGS)

include/grub/backtrace.h

@@ -0,0 +1,25 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2009  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef GRUB_BACKTRACE_HEADER
+#define GRUB_BACKTRACE_HEADER	1
+
+void grub_backtrace (void);
+void grub_backtrace_pointer (void *ptr);
+
+#endif

kern/i386/realmode.S

@@ -108,6 +108,12 @@ gdt:
 gdtdesc:
 	.word	0x27			/* limit */
 	.long	gdt			/* addr */
+realidt:
+	.word 0
+	.long 0
+protidt:
+	.word 0
+	.long 0
 
 /*
  *  These next two routines, "real_to_prot" and "prot_to_real" are structured
@@ -159,6 +165,9 @@ protcseg:
 	/* zero %eax */
 	xorl	%eax, %eax
 
+	sidt realidt
+	lidt protidt
+
 	/* return on the old (or initialized) stack! */
 	ret
 
@@ -166,6 +175,9 @@ prot_to_real:
 	/* just in case, set GDT */
 	lgdt	gdtdesc
 
+	sidt    protidt
+	lidt    realidt
+
 	/* save the protected mode stack */
 	movl	%esp, %eax
 	movl	%eax, protstack

lib/i386/backtrace.c

@@ -0,0 +1,194 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2009  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/misc.h>
+#include <grub/command.h>
+#include <grub/err.h>
+#include <grub/dl.h>
+#include <grub/mm.h>
+#include <grub/term.h>
+#include <grub/backtrace.h>
+
+#define MAX_STACK_FRAME 102400
+
+struct idt_descriptor
+{
+  grub_uint16_t limit;
+  void *base;
+} __attribute__ ((packed));
+
+#define GRUB_IDT_ENTRY_TYPE_PRESENT     0x80
+#define GRUB_IDT_ENTRY_TYPE_NOT_PRESENT 0x00
+#define GRUB_IDT_ENTRY_TYPE_RING0       0x00
+#define GRUB_IDT_ENTRY_TYPE_TRAP32      0x0f
+
+struct idt_entry
+{
+  grub_uint16_t addr_low;
+  grub_uint16_t segment;
+  grub_uint8_t unused;
+  grub_uint8_t type;
+  grub_uint16_t addr_high;
+} __attribute__ ((packed));
+
+void
+print_address (void *addr)
+{
+  const char *name;
+  int section;
+  grub_off_t off;
+  auto int hook (grub_dl_t mod);
+  int hook (grub_dl_t mod)
+  {
+    grub_dl_segment_t segment;
+    for (segment = mod->segment; segment; segment = segment->next)
+      if (segment->addr <= addr && (grub_uint8_t *) segment->addr
+	  + segment->size > (grub_uint8_t *) addr)
+	{
+	  name = mod->name;
+	  section = segment->section;
+	  off = (grub_uint8_t *) addr - (grub_uint8_t *) segment->addr;
+	  return 1;
+	}
+    return 0;
+  }
+
+  name = NULL;
+  grub_dl_iterate (hook);
+  if (name)
+    grub_printf ("%s.%x+%lx", name, section, (unsigned long) off);
+  else
+    grub_printf ("%p", addr);
+}
+
+void
+grub_backtrace_pointer (void *ebp)
+{
+  void *ptr, *nptr;
+  unsigned i;
+
+  ptr = ebp;
+  while (1)
+    {
+      grub_printf ("%p: ", ptr);
+      print_address (*(void **) (ptr + sizeof (void *)));
+      grub_printf (" (");
+      for (i = 0; i < 2; i++)
+	grub_printf ("%p,", *(void **)
+		     (ptr + (i + 2) * sizeof (void *)));
+      grub_printf ("%p", *(void **)
+		   (ptr + (i + 2) * sizeof (void *)));
+      grub_printf (")\n");
+      nptr = *(void **)ptr;
+      if (nptr < ptr || (void **) nptr - (void **) ptr > MAX_STACK_FRAME
+	  || nptr == ptr)
+	{
+	  grub_printf ("Invalid stack frame at %p (%p)\n", ptr, nptr);
+	  break;
+	}
+      ptr = nptr;
+    }
+}
+
+void
+grub_interrupt_handler_real (void *ret, void *ebp)
+{
+  grub_printf ("Unhandled exception at ");
+  print_address (ret);
+  grub_printf ("\n");
+  grub_backtrace_pointer (ebp);
+  grub_abort ();
+}
+
+
+void
+grub_backtrace (void)
+{
+#ifdef __x86_64__
+  asm volatile ("movq %rbp, %rdi\n"
+		"call grub_backtrace_pointer");
+#else
+  asm volatile ("movl %ebp, %eax\n"
+		"call grub_backtrace_pointer");
+#endif
+}
+
+static grub_err_t
+grub_cmd_backtrace (grub_command_t cmd __attribute__ ((unused)),
+		    int argc __attribute__ ((unused)),
+		    char **args __attribute__ ((unused)))
+{
+  grub_backtrace ();
+  return 0;
+}
+
+#define NUM_INTERRUPTS 0x20
+
+void grub_int_handler (void);
+
+struct idt_descriptor idt_desc;
+
+static grub_err_t
+setup_interrupts (void)
+{
+  struct idt_entry *idt_table;
+  unsigned long i;
+  grub_uint16_t seg;
+  idt_table = grub_memalign (0x10, NUM_INTERRUPTS * sizeof (struct idt_entry));
+  if (!idt_table)
+    return grub_errno;
+  idt_desc.base = idt_table;
+  idt_desc.limit = NUM_INTERRUPTS;
+
+  asm volatile ("xorl %%eax, %%eax\n"
+		"mov %%cs, %%ax\n" :"=a" (seg));
+
+  for (i = 0; i < NUM_INTERRUPTS; i++)
+    {
+      idt_table[i].addr_low = ((grub_addr_t) grub_int_handler) & 0xffff;
+      idt_table[i].addr_high = ((grub_addr_t) grub_int_handler) >> 16;
+      idt_table[i].unused = 0;
+      idt_table[i].segment = seg;
+      idt_table[i].type = GRUB_IDT_ENTRY_TYPE_PRESENT
+	| GRUB_IDT_ENTRY_TYPE_RING0 | GRUB_IDT_ENTRY_TYPE_TRAP32;
+    }
+
+  asm volatile ("lidt %0" : : "m" (idt_desc));
+
+  return GRUB_ERR_NONE;
+}
+
+static grub_command_t cmd;
+
+GRUB_MOD_INIT(backtrace)
+{
+  grub_err_t err;
+  err = setup_interrupts();
+  if (err)
+    {
+      grub_print_error ();
+      grub_errno = GRUB_ERR_NONE;
+    }
+  cmd = grub_register_command ("backtrace", grub_cmd_backtrace,
+			       0, "Print backtrace.");
+}
+
+GRUB_MOD_FINI(backtrace)
+{
+  grub_unregister_command (cmd);
+}

lib/i386/backtrace_int.S

@@ -0,0 +1,12 @@
+#include <grub/symbol.h>
+
+	.text
+	.p2align 4
+
+FUNCTION(grub_int_handler)
+	/* FIXME: push this only when CPU pushes no error on stack.  */
+	push $0
+	pusha
+	movl 36(%esp), %eax
+	movl %ebp, %edx
+	call EXT_C(grub_interrupt_handler_real)