2 files changed, 42 insertions, 14 deletions

diff --git a/sys/ddb/db_main.c b/sys/ddb/db_main.c
index 6e9286cbc1c1..bee321cc34ed 100644
--- a/sys/ddb/db_main.c
+++ b/sys/ddb/db_main.c
@@ -56,7 +56,12 @@ static dbbe_trace_thread_f db_trace_thread_wrapper;
 KDB_BACKEND(ddb, db_init, db_trace_self_wrapper, db_trace_thread_wrapper,
     db_trap);
 
-vm_offset_t ksym_start, ksym_end;
+/*
+ * Symbols can be loaded by specifying the exact addresses of
+ * the symtab and strtab in memory. This is used when loaded from
+ * boot loaders different than the native one (like Xen).
+ */
+vm_offset_t ksymtab, kstrtab, ksymtab_size;
 
 boolean_t
 X_db_line_at_pc(db_symtab_t *symtab, c_db_sym_t sym, char **file, int *line,
@@ -168,24 +173,39 @@ X_db_symbol_values(db_symtab_t *symtab, c_db_sym_t sym, const char **namep,
 	}
 }
 
+int
+db_fetch_ksymtab(vm_offset_t ksym_start, vm_offset_t ksym_end)
+{
+	Elf_Size strsz;
+
+	if (ksym_end > ksym_start && ksym_start != 0) {
+		ksymtab = ksym_start;
+		ksymtab_size = *(Elf_Size*)ksymtab;
+		ksymtab += sizeof(Elf_Size);
+		kstrtab = ksymtab + ksymtab_size;
+		strsz = *(Elf_Size*)kstrtab;
+		kstrtab += sizeof(Elf_Size);
+		if (kstrtab + strsz > ksym_end) {
+			/* Sizes doesn't match, unset everything. */
+			ksymtab = ksymtab_size = kstrtab = 0;
+		}
+	}
+
+	if (ksymtab == 0 || ksymtab_size == 0 || kstrtab == 0)
+		return (-1);
+
+	return (0);
+}
+
 static int
 db_init(void)
 {
-	uintptr_t symtab, strtab;
-	Elf_Size tabsz, strsz;
 
 	db_command_init();
-	if (ksym_end > ksym_start && ksym_start != 0) {
-		symtab = ksym_start;
-		tabsz = *((Elf_Size*)symtab);
-		symtab += sizeof(Elf_Size);
-		strtab = symtab + tabsz;
-		strsz = *((Elf_Size*)strtab);
-		strtab += sizeof(Elf_Size);
-		if (strtab + strsz <= ksym_end) {
-			db_add_symbol_table((char *)symtab,
-			    (char *)(symtab + tabsz), "elf", (char *)strtab);
-		}
+
+	if (ksymtab != 0 && kstrtab != 0 && ksymtab_size != 0) {
+		db_add_symbol_table((char *)ksymtab,
+		    (char *)(ksymtab + ksymtab_size), "elf", (char *)kstrtab);
 	}
 	db_add_symbol_table(NULL, NULL, "kld", NULL);
 	return (1);	/* We're the default debugger. */
diff --git a/sys/ddb/ddb.h b/sys/ddb/ddb.h
index 42fc9025954f..5aa646b3302a 100644
--- a/sys/ddb/ddb.h
+++ b/sys/ddb/ddb.h
@@ -77,6 +77,13 @@ int	DB_CALL(db_expr_t, db_expr_t *, int, db_expr_t[]);
 #endif
 
 /*
+ * Extern variables to set the address and size of the symtab and strtab.
+ * Most users should use db_fetch_symtab in order to set them from the
+ * boot loader provided values.
+ */
+extern vm_offset_t ksymtab, kstrtab, ksymtab_size;
+
+/*
  * There are three "command tables":
  * - One for simple commands; a list of these is displayed
  *   by typing 'help' at the debugger prompt.
@@ -218,6 +225,7 @@ int		db_value_of_name_vnet(const char *name, db_expr_t *valuep);
 int		db_write_bytes(vm_offset_t addr, size_t size, char *data);
 void		db_command_register(struct command_table *, struct command *);
 void		db_command_unregister(struct command_table *, struct command *);
+int		db_fetch_ksymtab(vm_offset_t ksym_start, vm_offset_t ksym_end);
 
 db_cmdfcn_t	db_breakpoint_cmd;
 db_cmdfcn_t	db_capture_cmd;