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Tue, 07 Apr 2020 08:30:21 -0700 (PDT) Subject: Re: [PATCH] gcc-plugins/stackleak: Avoid assignment for unused macro argument To: Kees Cook , kernel-hardening@lists.openwall.com Cc: Emese Revfy , linux-kernel@vger.kernel.org References: <202004020103.731F201@keescook> From: Alexander Popov Autocrypt: addr=alex.popov@linux.com; prefer-encrypt=mutual; keydata= mQINBFX15q4BEADZartsIW3sQ9R+9TOuCFRIW+RDCoBWNHhqDLu+Tzf2mZevVSF0D5AMJW4f UB1QigxOuGIeSngfmgLspdYe2Kl8+P8qyfrnBcS4hLFyLGjaP7UVGtpUl7CUxz2Hct3yhsPz ID/rnCSd0Q+3thrJTq44b2kIKqM1swt/F2Er5Bl0B4o5WKx4J9k6Dz7bAMjKD8pHZJnScoP4 dzKPhrytN/iWM01eRZRc1TcIdVsRZC3hcVE6OtFoamaYmePDwWTRhmDtWYngbRDVGe3Tl8bT 7BYN7gv7Ikt7Nq2T2TOfXEQqr9CtidxBNsqFEaajbFvpLDpUPw692+4lUbQ7FL0B1WYLvWkG cVysClEyX3VBSMzIG5eTF0Dng9RqItUxpbD317ihKqYL95jk6eK6XyI8wVOCEa1V3MhtvzUo WGZVkwm9eMVZ05GbhzmT7KHBEBbCkihS+TpVxOgzvuV+heCEaaxIDWY/k8u4tgbrVVk+tIVG 99v1//kNLqd5KuwY1Y2/h2MhRrfxqGz+l/f/qghKh+1iptm6McN//1nNaIbzXQ2Ej34jeWDa xAN1C1OANOyV7mYuYPNDl5c9QrbcNGg3D6gOeGeGiMn11NjbjHae3ipH8MkX7/k8pH5q4Lhh Ra0vtJspeg77CS4b7+WC5jlK3UAKoUja3kGgkCrnfNkvKjrkEwARAQABtCZBbGV4YW5kZXIg UG9wb3YgPGFsZXgucG9wb3ZAbGludXguY29tPokCVwQTAQgAQQIbIwIeAQIXgAULCQgHAwUV CgkICwUWAgMBAAIZARYhBLl2JLAkAVM0bVvWTo4Oneu8fo+qBQJdehKcBQkLRpLuAAoJEI4O neu8fo+qrkgP/jS0EhDnWhIFBnWaUKYWeiwR69DPwCs/lNezOu63vg30O9BViEkWsWwXQA+c SVVTz5f9eB9K2me7G06A3U5AblOJKdoZeNX5GWMdrrGNLVISsa0geXNT95TRnFqE1HOZJiHT NFyw2nv+qQBUHBAKPlk3eL4/Yev/P8w990Aiiv6/RN3IoxqTfSu2tBKdQqdxTjEJ7KLBlQBm 5oMpm/P2Y/gtBiXRvBd7xgv7Y3nShPUDymjBnc+efHFqARw84VQPIG4nqVhIei8gSWps49DX kp6v4wUzUAqFo+eh/ErWmyBNETuufpxZnAljtnKpwmpFCcq9yfcMlyOO9/viKn14grabE7qE 4j3/E60wraHu8uiXJlfXmt0vG16vXb8g5a25Ck09UKkXRGkNTylXsAmRbrBrA3Moqf8QzIk9 p+aVu/vFUs4ywQrFNvn7Qwt2hWctastQJcH3jrrLk7oGLvue5KOThip0SNicnOxVhCqstjYx KEnzZxtna5+rYRg22Zbfg0sCAAEGOWFXjqg3hw400oRxTW7IhiE34Kz1wHQqNif0i5Eor+TS 22r9iF4jUSnk1jaVeRKOXY89KxzxWhnA06m8IvW1VySHoY1ZG6xEZLmbp3OuuFCbleaW07OU 9L8L1Gh1rkAz0Fc9eOR8a2HLVFnemmgAYTJqBks/sB/DD0SuuQINBFX15q4BEACtxRV/pF1P XiGSbTNPlM9z/cElzo/ICCFX+IKg+byRvOMoEgrzQ28ah0N5RXQydBtfjSOMV1IjSb3oc23z oW2J9DefC5b8G1Lx2Tz6VqRFXC5OAxuElaZeoowV1VEJuN3Ittlal0+KnRYY0PqnmLzTXGA9 GYjw/p7l7iME7gLHVOggXIk7MP+O+1tSEf23n+dopQZrkEP2BKSC6ihdU4W8928pApxrX1Lt tv2HOPJKHrcfiqVuFSsb/skaFf4uveAPC4AausUhXQVpXIg8ZnxTZ+MsqlwELv+Vkm/SNEWl n0KMd58gvG3s0bE8H2GTaIO3a0TqNKUY16WgNglRUi0WYb7+CLNrYqteYMQUqX7+bB+NEj/4 8dHw+xxaIHtLXOGxW6zcPGFszaYArjGaYfiTTA1+AKWHRKvD3MJTYIonphy5EuL9EACLKjEF v3CdK5BLkqTGhPfYtE3B/Ix3CUS1Aala0L+8EjXdclVpvHQ5qXHs229EJxfUVf2ucpWNIUdf lgnjyF4B3R3BFWbM4Yv8QbLBvVv1Dc4hZ70QUXy2ZZX8keza2EzPj3apMcDmmbklSwdC5kYG EFT4ap06R2QW+6Nw27jDtbK4QhMEUCHmoOIaS9j0VTU4fR9ZCpVT/ksc2LPMhg3YqNTrnb1v RVNUZvh78zQeCXC2VamSl9DMcwARAQABiQI8BBgBCAAmAhsMFiEEuXYksCQBUzRtW9ZOjg6d 67x+j6oFAl16ErcFCQtGkwkACgkQjg6d67x+j6q7zA/+IsjSKSJypgOImN9LYjeb++7wDjXp qvEpq56oAn21CvtbGus3OcC0hrRtyZ/rC5Qc+S5SPaMRFUaK8S3j1vYC0wZJ99rrmQbcbYMh C2o0k4pSejaINmgyCajVOhUhln4IuwvZke1CLfXe1i3ZtlaIUrxfXqfYpeijfM/JSmliPxwW BRnQRcgS85xpC1pBUMrraxajaVPwu7hCTke03v6bu8zSZlgA1rd9E6KHu2VNS46VzUPjbR77 kO7u6H5PgQPKcuJwQQ+d3qa+5ZeKmoVkc2SuHVrCd1yKtAMmKBoJtSku1evXPwyBzqHFOInk mLMtrWuUhj+wtcnOWxaP+n4ODgUwc/uvyuamo0L2Gp3V5ItdIUDO/7ZpZ/3JxvERF3Yc1md8 5kfflpLzpxyl2fKaRdvxr48ZLv9XLUQ4qNuADDmJArq/+foORAX4BBFWvqZQKe8a9ZMAvGSh uoGUVg4Ks0uC4IeG7iNtd+csmBj5dNf91C7zV4bsKt0JjiJ9a4D85dtCOPmOeNuusK7xaDZc gzBW8J8RW+nUJcTpudX4TC2SGeAOyxnM5O4XJ8yZyDUY334seDRJWtS4wRHxpfYcHKTewR96 IsP1USE+9ndu6lrMXQ3aFsd1n1m1pfa/y8hiqsSYHy7JQ9Iuo9DxysOj22UNOmOE+OYPK48D j3lCqPk= Message-ID: <13c90df4-a422-bb73-a119-b8ccd11fc4f1@linux.com> Date: Tue, 7 Apr 2020 18:30:18 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <202004020103.731F201@keescook> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Hello Kees, On 02.04.2020 11:10, Kees Cook wrote: > With GCC version >= 8, the cgraph_create_edge() macro argument using > "frequency" goes unused. Instead of assigning a temporary variable for > the argument, pass the compute_call_stmt_bb_frequency() call directly > as the macro argument so that it will just not be uncalled when it is > not wanted by the macros. Do you mean "it will just not be called"? Thanks! > Silences the warning: > > scripts/gcc-plugins/stackleak_plugin.c:54:6: warning: variable ‘frequency’ set but not used [-Wunused-but-set-variable] > > Now builds cleanly with gcc-7 and gcc-9. Both boot and pass > STACKLEAK_ERASING LKDTM test. > > Signed-off-by: Kees Cook > --- > scripts/gcc-plugins/stackleak_plugin.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c > index dbd37460c573..cc75eeba0be1 100644 > --- a/scripts/gcc-plugins/stackleak_plugin.c > +++ b/scripts/gcc-plugins/stackleak_plugin.c > @@ -51,7 +51,6 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after) > gimple stmt; > gcall *stackleak_track_stack; > cgraph_node_ptr node; > - int frequency; > basic_block bb; > > /* Insert call to void stackleak_track_stack(void) */ > @@ -68,9 +67,9 @@ static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after) > bb = gimple_bb(stackleak_track_stack); > node = cgraph_get_create_node(track_function_decl); > gcc_assert(node); > - frequency = compute_call_stmt_bb_frequency(current_function_decl, bb); > cgraph_create_edge(cgraph_get_node(current_function_decl), node, > - stackleak_track_stack, bb->count, frequency); > + stackleak_track_stack, bb->count, > + compute_call_stmt_bb_frequency(current_function_decl, bb)); > } > > static bool is_alloca(gimple stmt) >