[tip:core/objtool] objtool: Detect infinite recursion

[tip-bot for Josh Poimboeuf]

Commit-ID:  b1e03249510b32645826bbf61a1452dd766c2e5c
Gitweb: http://git.kernel.org/tip/b1e03249510b32645826bbf61a1452dd766c2e5c
Author: Josh Poimboeuf 
AuthorDate: Wed, 9 Mar 2016 00:06:52 -0600
Committer:  Ingo Molnar 
CommitDate: Wed, 9 Mar 2016 10:48:07 +0100

objtool: Detect infinite recursion

I don't _think_ dead_end_function() can get into a recursive loop, but
just in case, stop the loop and print a warning.

Signed-off-by: Josh Poimboeuf 
Cc: Andrew Morton 
Cc: Andy Lutomirski 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Bernd Petrovitsch 
Cc: Borislav Petkov 
Cc: Chris J Arges 
Cc: Jiri Slaby 
Cc: Linus Torvalds 
Cc: Michal Marek 
Cc: Namhyung Kim 
Cc: Pedro Alves 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: live-patch...@vger.kernel.org
Link: 
http://lkml.kernel.org/r/ff489a63e6feb88abb192cfb361d81626dcf3e89.1457502970.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar 
---
 tools/objtool/builtin-check.c | 45 +++
 1 file changed, 33 insertions(+), 12 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 80d9ed9..51da270 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -121,8 +121,14 @@ static bool ignore_func(struct objtool_file *file, struct 
symbol *func)
  *
  * For local functions, we have to detect them manually by simply looking for
  * the lack of a return instruction.
+ *
+ * Returns:
+ *  -1: error
+ *   0: no dead end
+ *   1: dead end
  */
-static bool dead_end_function(struct objtool_file *file, struct symbol *func)
+static int __dead_end_function(struct objtool_file *file, struct symbol *func,
+  int recursion)
 {
int i;
struct instruction *insn, *func_insn;
@@ -144,19 +150,19 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
};
 
if (func->bind == STB_WEAK)
-   return false;
+   return 0;
 
if (func->bind == STB_GLOBAL)
for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
if (!strcmp(func->name, global_noreturns[i]))
-   return true;
+   return 1;
 
if (!func->sec)
-   return false;
+   return 0;
 
func_insn = find_instruction(file, func->sec, func->offset);
if (!func_insn)
-   return false;
+   return 0;
 
insn = func_insn;
list_for_each_entry_from(insn, >insns, list) {
@@ -167,11 +173,11 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
empty = false;
 
if (insn->type == INSN_RETURN)
-   return false;
+   return 0;
}
 
if (empty)
-   return false;
+   return 0;
 
/*
 * A function can have a sibling call instead of a return.  In that
@@ -190,7 +196,7 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
 
if (!dest)
/* sibling call to another file */
-   return false;
+   return 0;
 
if (dest->sec != func->sec ||
dest->offset < func->offset ||
@@ -201,16 +207,28 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
if (!dest_func)
continue;
 
-   return dead_end_function(file, dest_func);
+   if (recursion == 5) {
+   WARN_FUNC("infinite recursion (objtool 
bug!)",
+ dest->sec, dest->offset);
+   return -1;
+   }
+
+   return __dead_end_function(file, dest_func,
+  recursion + 1);
}
}
 
if (insn->type == INSN_JUMP_DYNAMIC)
/* sibling call */
-   return false;
+   return 0;
}
 
-   return true;
+   return 1;
+}
+
+static int dead_end_function(struct objtool_file *file, struct symbol *func)
+{
+   return __dead_end_function(file, func, 0);
 }
 
 /*
@@ -809,8 +827,11 @@ static int validate_branch(struct 

[tip:core/objtool] objtool: Detect infinite recursion

[tip-bot for Josh Poimboeuf]

Commit-ID:  b1e03249510b32645826bbf61a1452dd766c2e5c
Gitweb: http://git.kernel.org/tip/b1e03249510b32645826bbf61a1452dd766c2e5c
Author: Josh Poimboeuf 
AuthorDate: Wed, 9 Mar 2016 00:06:52 -0600
Committer:  Ingo Molnar 
CommitDate: Wed, 9 Mar 2016 10:48:07 +0100

objtool: Detect infinite recursion

I don't _think_ dead_end_function() can get into a recursive loop, but
just in case, stop the loop and print a warning.

Signed-off-by: Josh Poimboeuf 
Cc: Andrew Morton 
Cc: Andy Lutomirski 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Bernd Petrovitsch 
Cc: Borislav Petkov 
Cc: Chris J Arges 
Cc: Jiri Slaby 
Cc: Linus Torvalds 
Cc: Michal Marek 
Cc: Namhyung Kim 
Cc: Pedro Alves 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: live-patch...@vger.kernel.org
Link: 
http://lkml.kernel.org/r/ff489a63e6feb88abb192cfb361d81626dcf3e89.1457502970.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar 
---
 tools/objtool/builtin-check.c | 45 +++
 1 file changed, 33 insertions(+), 12 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 80d9ed9..51da270 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -121,8 +121,14 @@ static bool ignore_func(struct objtool_file *file, struct 
symbol *func)
  *
  * For local functions, we have to detect them manually by simply looking for
  * the lack of a return instruction.
+ *
+ * Returns:
+ *  -1: error
+ *   0: no dead end
+ *   1: dead end
  */
-static bool dead_end_function(struct objtool_file *file, struct symbol *func)
+static int __dead_end_function(struct objtool_file *file, struct symbol *func,
+  int recursion)
 {
int i;
struct instruction *insn, *func_insn;
@@ -144,19 +150,19 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
};
 
if (func->bind == STB_WEAK)
-   return false;
+   return 0;
 
if (func->bind == STB_GLOBAL)
for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
if (!strcmp(func->name, global_noreturns[i]))
-   return true;
+   return 1;
 
if (!func->sec)
-   return false;
+   return 0;
 
func_insn = find_instruction(file, func->sec, func->offset);
if (!func_insn)
-   return false;
+   return 0;
 
insn = func_insn;
list_for_each_entry_from(insn, >insns, list) {
@@ -167,11 +173,11 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
empty = false;
 
if (insn->type == INSN_RETURN)
-   return false;
+   return 0;
}
 
if (empty)
-   return false;
+   return 0;
 
/*
 * A function can have a sibling call instead of a return.  In that
@@ -190,7 +196,7 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
 
if (!dest)
/* sibling call to another file */
-   return false;
+   return 0;
 
if (dest->sec != func->sec ||
dest->offset < func->offset ||
@@ -201,16 +207,28 @@ static bool dead_end_function(struct objtool_file *file, 
struct symbol *func)
if (!dest_func)
continue;
 
-   return dead_end_function(file, dest_func);
+   if (recursion == 5) {
+   WARN_FUNC("infinite recursion (objtool 
bug!)",
+ dest->sec, dest->offset);
+   return -1;
+   }
+
+   return __dead_end_function(file, dest_func,
+  recursion + 1);
}
}
 
if (insn->type == INSN_JUMP_DYNAMIC)
/* sibling call */
-   return false;
+   return 0;
}
 
-   return true;
+   return 1;
+}
+
+static int dead_end_function(struct objtool_file *file, struct symbol *func)
+{
+   return __dead_end_function(file, func, 0);
 }
 
 /*
@@ -809,8 +827,11 @@ static int validate_branch(struct objtool_file *file,
break;
}
 
-   if (dead_end_function(file, insn->call_dest))
+   ret = dead_end_function(file, insn->call_dest);
+   if (ret == 1)
return warnings;
+   if (ret == -1)
+