From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from relay12.mail.gandi.net ([217.70.178.232]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iBDoN-0001P4-5S for barebox@lists.infradead.org; Fri, 20 Sep 2019 07:58:41 +0000 Received: from geraet.fritz.box (muedsl-82-207-195-051.citykom.de [82.207.195.51]) (Authenticated sender: ahmad@a3f.at) by relay12.mail.gandi.net (Postfix) with ESMTPSA id 092A7200008 for ; Fri, 20 Sep 2019 07:58:21 +0000 (UTC) From: Ahmad Fatoum Date: Fri, 20 Sep 2019 09:58:12 +0200 Message-Id: <20190920075813.22471-3-ahmad@a3f.at> In-Reply-To: <20190920075813.22471-1-ahmad@a3f.at> References: <20190920075813.22471-1-ahmad@a3f.at> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: [PATCH v1 3/4] common: ubsan: ignore shifting one into sign bit To: barebox@lists.infradead.org The __ubsan_handle_shift_out_of_bounds handler would be called for code shifting a one into the sign bit like (1 << 31), which is all too common in barebox. It's technically UB, but it's so prevalent that it's highly unlikely to be treated by a compiler as anything else than the standard-compliant (1U << 31). Check for this case here and ignore it selectively. Signed-off-by: Ahmad Fatoum --- lib/ubsan.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/lib/ubsan.c b/lib/ubsan.c index 89ca6e580bce..41a5731dda66 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -382,6 +382,26 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, if (suppress_report(&data->location)) return; + /* This handler would be called for code shifting a one into the + * sign bit like (1 << 31), which is all too common in barebox. + * It's technically UB, but it's so prevalent that it's highly + * unlikely to be treated by a compiler as anything else than the + * standard-compliant (1U << 31). Thus check for this case here + * and ignore it selectively + */ + if (type_is_signed(lhs_type)) { + s_max lhs_int, rhs_int; + + lhs_int = get_signed_val(lhs_type, lhs); + rhs_int = get_signed_val(rhs_type, rhs); + + if (fls(lhs_int) + rhs_int == type_bit_width(lhs_type)) { + pr_debug("signed left shift of %lld by %lld ignored.\n", + (s64)lhs_int, (s64)rhs_int); + return; + } + } + ubsan_prologue(&data->location, &flags); val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs); -- 2.20.1 _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox