From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33825) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZwcVM-0000Af-Qd for qemu-devel@nongnu.org; Wed, 11 Nov 2015 16:00:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZwcVH-0000jZ-Ql for qemu-devel@nongnu.org; Wed, 11 Nov 2015 16:00:32 -0500 From: Rodrigo Rebello Date: Wed, 11 Nov 2015 18:57:37 -0200 Message-Id: <1447275457-1415-1-git-send-email-rprebello@gmail.com> Subject: [Qemu-devel] [PATCH 1/1] configure: use appropriate code fragment for -fstack-protector checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-trivial@nongnu.org, Rodrigo Rebello The check for stack-protector support consisted in compiling and linking the test program below (output by function write_c_skeleton()) with the compiler flag -fstack-protector-strong first and then with -fstack-protector-all if the first one failed to work: int main(void) { return 0; } This caused false positives when using certain toolchains in which the compiler accepted -fstack-protector-strong but no support was provided by the C library, since for this stack-protector variant the compiler emits canary code only for functions that meet specific conditions (local arrays, memory references to local variables, etc.) and the code fragment under test included none of them (hence no stack protection code generated, no link failure). This fix changes the test program used for -fstack-protector checks to include a function that meets conditions which cause the compiler to generate canary code in all variants. Signed-off-by: Rodrigo Rebello --- configure | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/configure b/configure index 46fd8bd..c3d9592 100755 --- a/configure +++ b/configure @@ -1486,6 +1486,24 @@ for flag in $gcc_flags; do done if test "$stack_protector" != "no"; then + cat > $TMPC << EOF +void foo(const char *c); + +void foo(const char *c) +{ + char arr[64], *p; + for (p = arr; *c; c++, p++) { + *p = *c; + } +} + +int main(void) +{ + char c[] = ""; + foo(c); + return 0; +} +EOF gcc_flags="-fstack-protector-strong -fstack-protector-all" sp_on=0 for flag in $gcc_flags; do -- 2.1.4