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* [PATCH] objtool: Fix infinite loop in find_jump_table()
@ 2020-04-28 21:45 Josh Poimboeuf
  2020-04-28 22:40 ` Peter Zijlstra
  2020-05-07 15:28 ` [tip: objtool/urgent] " tip-bot2 for Josh Poimboeuf
  0 siblings, 2 replies; 3+ messages in thread
From: Josh Poimboeuf @ 2020-04-28 21:45 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Peter Zijlstra, Miroslav Benes, Julien Thierry,
	Kristen Carlson Accardi

Kristen found a hang in objtool when building with -ffunction-sections.

It was caused by evergreen_pcie_gen2_enable.cold() being laid out
immediately before evergreen_pcie_gen2_enable().  Since their "pfunc" is
always the same, find_jump_table() got into an infinite loop because it
didn't recognize the boundary between the two functions.

Fix that with a new prev_insn_same_sym() helper, which doesn't cross
subfunction boundaries.

Reported-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0c732d586924..4b51a06c7683 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -73,6 +73,17 @@ static struct instruction *next_insn_same_func(struct objtool_file *file,
 	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
 }
 
+static struct instruction *prev_insn_same_sym(struct objtool_file *file,
+					       struct instruction *insn)
+{
+	struct instruction *prev = list_prev_entry(insn, list);
+
+	if (&prev->list != &file->insn_list && prev->func == insn->func)
+		return prev;
+
+	return NULL;
+}
+
 #define func_for_each_insn(file, func, insn)				\
 	for (insn = find_insn(file, func->sec, func->offset);		\
 	     insn;							\
@@ -1096,8 +1107,8 @@ static struct rela *find_jump_table(struct objtool_file *file,
 	 * it.
 	 */
 	for (;
-	     &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
-	     insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
+	     insn && insn->func && insn->func->pfunc == func;
+	     insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
 
 		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
 			break;
-- 
2.21.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH] objtool: Fix infinite loop in find_jump_table()
  2020-04-28 21:45 [PATCH] objtool: Fix infinite loop in find_jump_table() Josh Poimboeuf
@ 2020-04-28 22:40 ` Peter Zijlstra
  2020-05-07 15:28 ` [tip: objtool/urgent] " tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2020-04-28 22:40 UTC (permalink / raw)
  To: Josh Poimboeuf
  Cc: x86, linux-kernel, Miroslav Benes, Julien Thierry,
	Kristen Carlson Accardi

On Tue, Apr 28, 2020 at 04:45:16PM -0500, Josh Poimboeuf wrote:
> Kristen found a hang in objtool when building with -ffunction-sections.
> 
> It was caused by evergreen_pcie_gen2_enable.cold() being laid out
> immediately before evergreen_pcie_gen2_enable().  Since their "pfunc" is
> always the same, find_jump_table() got into an infinite loop because it
> didn't recognize the boundary between the two functions.
> 
> Fix that with a new prev_insn_same_sym() helper, which doesn't cross
> subfunction boundaries.
> 
> Reported-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread

* [tip: objtool/urgent] objtool: Fix infinite loop in find_jump_table()
  2020-04-28 21:45 [PATCH] objtool: Fix infinite loop in find_jump_table() Josh Poimboeuf
  2020-04-28 22:40 ` Peter Zijlstra
@ 2020-05-07 15:28 ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2020-05-07 15:28 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Kristen Carlson Accardi, Josh Poimboeuf, Peter Zijlstra (Intel),
	x86, LKML

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     1119d265bc20226c241e5540fc8a246d9e30b272
Gitweb:        https://git.kernel.org/tip/1119d265bc20226c241e5540fc8a246d9e30b272
Author:        Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate:    Tue, 28 Apr 2020 16:45:16 -05:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 07 May 2020 17:22:31 +02:00

objtool: Fix infinite loop in find_jump_table()

Kristen found a hang in objtool when building with -ffunction-sections.

It was caused by evergreen_pcie_gen2_enable.cold() being laid out
immediately before evergreen_pcie_gen2_enable().  Since their "pfunc" is
always the same, find_jump_table() got into an infinite loop because it
didn't recognize the boundary between the two functions.

Fix that with a new prev_insn_same_sym() helper, which doesn't cross
subfunction boundaries.

Reported-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/378b51c9d9c894dc3294bc460b4b0869e950b7c5.1588110291.git.jpoimboe@redhat.com
---
 tools/objtool/check.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4b170fd..0e8f9a3 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -72,6 +72,17 @@ static struct instruction *next_insn_same_func(struct objtool_file *file,
 	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
 }
 
+static struct instruction *prev_insn_same_sym(struct objtool_file *file,
+					       struct instruction *insn)
+{
+	struct instruction *prev = list_prev_entry(insn, list);
+
+	if (&prev->list != &file->insn_list && prev->func == insn->func)
+		return prev;
+
+	return NULL;
+}
+
 #define func_for_each_insn(file, func, insn)				\
 	for (insn = find_insn(file, func->sec, func->offset);		\
 	     insn;							\
@@ -1050,8 +1061,8 @@ static struct rela *find_jump_table(struct objtool_file *file,
 	 * it.
 	 */
 	for (;
-	     &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
-	     insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
+	     insn && insn->func && insn->func->pfunc == func;
+	     insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
 
 		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
 			break;

^ permalink raw reply related	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2020-05-07 15:28 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-04-28 21:45 [PATCH] objtool: Fix infinite loop in find_jump_table() Josh Poimboeuf
2020-04-28 22:40 ` Peter Zijlstra
2020-05-07 15:28 ` [tip: objtool/urgent] " tip-bot2 for Josh Poimboeuf

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