From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A25FE846A; Sun, 27 Sep 2026 00:57:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790470654; cv=none; b=D8d99eMFIXBuOa5w+guphAOOJ6XBlKCdZRlxbTK/4AHjM5fpbM9RTl3zrF+4F03C1kYZhIAO90fIZOLBMgIanGbG4N+X/fT1oQOx/ShkOH3JE/YAtzWI5/r9jqdqbJMPOaNCe0GR3VHckWwz5LbpgECSW5EHZzUxNoTsFw+Oz80= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790470654; c=relaxed/simple; bh=kWIOhGRUlAQyfvB6LGJ7tanRtsf+WUVQo1enbwMxuLw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=F5nF/nu12ApivQ5SxDdZNYQTGVEfhs9GhSO1fqyTpYoLvNME6EfV3jpfUOg5RlH+40trOOeudKvMotsvW/7NXTVbs/xZSI78ycEDOPoXk7hLXStMGKQi0M18FQN3ycb/iyTkWmKA3omdimyGioSrbDiPM6kiCFdXj/YlV5w4r2E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BFvrXsK4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BFvrXsK4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E19A51F000FF; Sun, 27 Sep 2026 00:57:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790470653; bh=mlGblNF0KjkLghO+zmfgnegg8eN2gwMPX91bcyPsmTw=; h=From:To:Cc:Subject:Date; b=BFvrXsK4Z2evgqJht13bk8twZr1rA0W6y6Yaj44gk28lZyGl0o8dM3b5S3YtNlIZO knkE1+eFF4LZz0OKFCTu57sY7YDLFZ66brfNeEEiMkgSlqeuTW0fXMyrPqo4NIxJy0 2cEv1Hq+MtNqi4xsqMjNkDIqi/QZUaXZX1kzGrWynoipmap3GGaYp8fSr+9dbPX/OW fFETXxYRJmchojdxtrMcryp8iABdQFNRJskE740OCGbnbCP8cTZnEYnCViv800SUnA V5zSw/KKRU8PZTO4dOxNhjEsSBCiZtm7oEDeNu0rERl5d7Dku1IYwTqSYYXeT3e8sg rjZX0B6Vm/HLA== From: Imre Kaloz To: Andreas Larsson , sparclinux@vger.kernel.org Cc: "David S. Miller" , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] math-emu: fix wrong word index in _FP_FRAC_CLZ_4 Date: Sun, 27 Sep 2026 02:56:30 +0200 Message-ID: <20260927005630.8202-1-kaloz@kernel.org> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit _FP_FRAC_CLZ_4 picks a word by testing X##_f[3], X##_f[2] and X##_f[1] in turn and counts the leading zeros of the first non-zero one. The X##_f[1] branch passes X##_f[2] to __FP_CLZ, a word already known to be zero, so the result is 3 * _FP_W_TYPE_SIZE - 1 whatever X##_f[1] holds. Normalizing a quad then shifts by up to a word too much whenever the leading set bit falls in word 1. sparc traps every quad operation to do_mathemu(), so hex floats parsed by strtod() and scanf() in ordinary user code come back wrong. With this, the affected float-parse tests pass on a SPARCstation 20. The wrong index has been there since 2.1.97. Cc: stable@vger.kernel.org Signed-off-by: Imre Kaloz --- Notes: - _FP_FRAC_CLZ_4 is the generic 4-word helper in include/math-emu/op-4.h, which is why LKML is on Cc. - The checkpatch error "space required after that ','" is the surrounding soft-fp idiom: every neighbouring line in op-4.h is written __FP_CLZ(R,X##_f[N]). - No Fixes: tag: this has been broken since 2.1.97, before the git history. checkpatch asks for one to go with the stable@ Cc, but there is no commit to name. include/math-emu/op-4.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/math-emu/op-4.h b/include/math-emu/op-4.h index ba226f8237a6..429c8f5cbf8a 100644 --- a/include/math-emu/op-4.h +++ b/include/math-emu/op-4.h @@ -170,7 +170,7 @@ } \ else if (X##_f[1]) \ { \ - __FP_CLZ(R,X##_f[2]); \ + __FP_CLZ(R,X##_f[1]); \ R += _FP_W_TYPE_SIZE*2; \ } \ else \ base-commit: 62f4c998b297cf233997a2b4cd6fc2d2df0319c9 -- 2.47.3