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[PATCH 04/17] libebl: Use static number for array stack allocation in openbackend.
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Sat, 23 May 2015 23:10:17 +0200
- Subject: [PATCH 04/17] libebl: Use static number for array stack allocation in openbackend.
Help the compiler see we stack allocate a small array. Add assert to check
no machine prefix is ever larger than 16. Current maximum number is 7.
This prevents gcc warning about possible unbounded stack usage with
-Wstack-usage.
Signed-off-by: Mark Wielaard <mjw@redhat.com>
---
libebl/ChangeLog | 5 +++++
libebl/eblopenbackend.c | 10 ++++++++--
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/libebl/ChangeLog b/libebl/ChangeLog
index 3655e72..9ca7b47 100644
--- a/libebl/ChangeLog
+++ b/libebl/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-17 Mark Wielaard <mjw@redhat.com>
+
+ * eblopenbackend.c (MAX_PREFIX_LEN): New define (16).
+ (openbackend): Stack allocate symname array using MAX_PREFIX_LEN.
+
2015-01-27 Mark Wielaard <mjw@redhat.com>
* libebl.h: Add comment from README that this is completely
diff --git a/libebl/eblopenbackend.c b/libebl/eblopenbackend.c
index 3a22f53..2766e7b 100644
--- a/libebl/eblopenbackend.c
+++ b/libebl/eblopenbackend.c
@@ -1,5 +1,5 @@
/* Generate ELF backend handle.
- Copyright (C) 2000-2014 Red Hat, Inc.
+ Copyright (C) 2000-2015 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -135,6 +135,8 @@ static const struct
};
#define nmachines (sizeof (machines) / sizeof (machines[0]))
+/* No machine prefix should be larger than this. */
+#define MAX_PREFIX_LEN 16
/* Default callbacks. Mostly they just return the error value. */
static const char *default_object_type_name (int ignore, char *buf,
@@ -343,7 +345,11 @@ openbackend (elf, emulation, machine)
static const char version[] = MODVERSION;
const char *modversion;
ebl_bhinit_t initp;
- char symname[machines[cnt].prefix_len + sizeof "_init"];
+
+ // We use a static number to help the compiler see we don't
+ // overflow the stack with an arbitrary number.
+ assert (machines[cnt].prefix_len <= MAX_PREFIX_LEN);
+ char symname[MAX_PREFIX_LEN + sizeof "_init"];
strcpy (mempcpy (symname, machines[cnt].prefix,
machines[cnt].prefix_len), "_init");
--
1.8.3.1