From patchwork Tue Aug 20 05:08:47 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Henderson X-Patchwork-Id: 13769319 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1BDAEC3DA4A for ; Tue, 20 Aug 2024 05:09:54 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sgH7Q-0004PP-7P; Tue, 20 Aug 2024 01:09:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sgH7A-0004LU-FU for qemu-devel@nongnu.org; Tue, 20 Aug 2024 01:09:05 -0400 Received: from mail-oa1-x35.google.com ([2001:4860:4864:20::35]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1sgH77-0007q0-HT for qemu-devel@nongnu.org; Tue, 20 Aug 2024 01:09:04 -0400 Received: by mail-oa1-x35.google.com with SMTP id 586e51a60fabf-2704d461058so1541068fac.0 for ; Mon, 19 Aug 2024 22:09:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1724130540; x=1724735340; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=z/V+/zK9f6DneOT0stD1zbRm+cUo+xuW5miljh1QM8Q=; b=dvC/ETQRSGZ4XlRWPF3Cla6m8ZCxk8XrFRzuq2N2AttOy0JLds608Oaz2L82Qo2FrL gHf8O3UN3E870TlgrrKAiKx1whELzkGg1O8TOtnLf6Q4WYkV2fzZK4hEGXX6zSM3LWHc JPh30gs+VP+Dqt0UbPMV4Hkx0566NUSruOZZXaZ3gmN8US/A38jLmzo9dpUzBj8UiVct rX7lxuRly2sN1GBX786zTloH8ijGMrhrj2dLefBR5+otajQfKgpmNv1GQwHvPVeY3jQx tlLDrYZE9ChbB0cvO09+1EECWBffyPcvCPnRLdsPMZClonP/tecNSrSR0LZmYkRO4qyx XTRA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724130540; x=1724735340; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=z/V+/zK9f6DneOT0stD1zbRm+cUo+xuW5miljh1QM8Q=; b=UxfAfLOi23QUXubUn5LtDAhnNMyYguvDDEEHiCENZheBKQYVoeBcTd7VPSUxhbtZfJ sw1yhk6QZYGQqNLT+YP1xnWIaaQR60aeGcwBxGEGDex2lCmeZj2FNDiiJcQfCi1RseDz 8kQMs83vYHDSVwCkffmifzSddyATO4jX8nMenMDfvfKaingOqf9YaA/xRL9Va0wAW6iT S/pZ3KVswOZNlSWeYxNv3YRMg+I6oPj3OPgTXsf0h6ZbYDOqiDL6gmt40sa1w31QNaJN 6Qt8AHLlUB18i/raIOR2Jjh5Xi8NMFRXliB2PPYH10/MZshi9/dNorcsZHwB4fhi436t pfiQ== X-Gm-Message-State: AOJu0YxmSmm08f6Rg0CLYopCagimQW/VPY6ZuvmkgxjhGZJJggpCH3f/ QjOlG/wj4BFRnlf3+cKuGhHvzzaHB0nIpNSxFIfJ1d0o6jsNi//v57tWM6oMMev8Y9QzWbGGSyF 96CY= X-Google-Smtp-Source: AGHT+IGApbUlEljK6DxsVx9YsxklWq8nSaeVXvdWqH4JlCF9r/yuHl2DRYhQvp1RZMA7VQO098D3tg== X-Received: by 2002:a05:6870:d607:b0:261:1eb4:dd8e with SMTP id 586e51a60fabf-2701c3450e3mr15351560fac.2.1724130539755; Mon, 19 Aug 2024 22:08:59 -0700 (PDT) Received: from stoup.. ([203.30.3.188]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7127af416fbsm7382814b3a.207.2024.08.19.22.08.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Aug 2024 22:08:59 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: gaosong@loongson.cn, philmd@linaro.org, imp@bsdimp.com, qemu-stable@nongnu.org Subject: [PATCH v2 1/2] linux-user: Handle short reads in mmap_h_gt_g Date: Tue, 20 Aug 2024 15:08:47 +1000 Message-ID: <20240820050848.165253-2-richard.henderson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240820050848.165253-1-richard.henderson@linaro.org> References: <20240820050848.165253-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2001:4860:4864:20::35; envelope-from=richard.henderson@linaro.org; helo=mail-oa1-x35.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org In particular, if an image has a large bss, we can hit EOF before reading all host_len bytes of the mapping. Create a helper, mmap_pread to handle the job for both the larger block in mmap_h_gt_g itself, as well as the smaller block in mmap_frag. Cc: qemu-stable@nongnu.org Fixes: eb5027ac618 ("linux-user: Split out mmap_h_gt_g") Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2504 Signed-off-by: Richard Henderson --- linux-user/mmap.c | 44 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 38 insertions(+), 6 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 6418e811f6..e4bf5d5f39 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -283,6 +283,40 @@ static int do_munmap(void *addr, size_t len) return munmap(addr, len); } +/* + * Perform a pread on behalf of target_mmap. We can reach EOF, we can be + * interrupted by signals, and in general there's no good error return path. + * If @zero, zero the rest of the block at EOF. + * Return true on success. + */ +static bool mmap_pread(int fd, void *p, size_t len, off_t offset, bool zero) +{ + while (1) { + ssize_t r = pread(fd, p, len, offset); + + if (likely(r == len)) { + /* Complete */ + return true; + } + if (r == 0) { + /* EOF */ + if (zero) { + memset(p, 0, len); + } + return true; + } + if (r > 0) { + /* Short read */ + p += r; + len -= r; + offset += r; + } else if (errno != EINTR) { + /* Error */ + return false; + } + } +} + /* * Map an incomplete host page. * @@ -357,10 +391,9 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, /* Read or zero the new guest pages. */ if (flags & MAP_ANONYMOUS) { memset(g2h_untagged(start), 0, last - start + 1); - } else { - if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) { - return false; - } + } else if (!mmap_pread(fd, g2h_untagged(start), last - start + 1, + offset, true)) { + return false; } /* Put final protection */ @@ -853,8 +886,7 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len, } if (misaligned_offset) { - /* TODO: The read could be short. */ - if (pread(fd, p, host_len, offset + real_start - start) != host_len) { + if (!mmap_pread(fd, p, host_len, offset + real_start - start, false)) { do_munmap(p, host_len); return -1; }