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Wed, 02 Aug 2023 00:18:10 -0700 (PDT) Received: from alarm.flets-east.jp ([2400:4050:a840:1e00:78d2:b862:10a7:d486]) by smtp.gmail.com with ESMTPSA id x12-20020a63b20c000000b00528da88275bsm11004440pge.47.2023.08.02.00.18.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Aug 2023 00:18:09 -0700 (PDT) From: Akihiko Odaki To: Cc: Helge Deller , Joel Stanley , Michael Tokarev , qemu-devel@nongnu.org, Laurent Vivier , Peter Maydell , Richard Henderson , Akihiko Odaki Subject: [PATCH v2 4/6] linux-user: Use MAP_FIXED_NOREPLACE for do_brk() Date: Wed, 2 Aug 2023 16:17:50 +0900 Message-ID: <20230802071754.14876-5-akihiko.odaki@daynix.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230802071754.14876-1-akihiko.odaki@daynix.com> References: <20230802071754.14876-1-akihiko.odaki@daynix.com> MIME-Version: 1.0 Received-SPF: none client-ip=2607:f8b0:4864:20::32d; envelope-from=akihiko.odaki@daynix.com; helo=mail-ot1-x32d.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org MAP_FIXED_NOREPLACE can ensure the mapped address is fixed without concerning that the new mapping overwrites something else. Signed-off-by: Akihiko Odaki --- linux-user/syscall.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index b9d2ec02f9..ac429a185a 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -854,17 +854,12 @@ abi_long do_brk(abi_ulong brk_val) return target_brk; } - /* We need to allocate more memory after the brk... Note that - * we don't use MAP_FIXED because that will map over the top of - * any existing mapping (like the one with the host libc or qemu - * itself); instead we treat "mapped but at wrong address" as - * a failure and unmap again. - */ if (new_host_brk_page > brk_page) { new_alloc_size = new_host_brk_page - brk_page; mapped_addr = target_mmap(brk_page, new_alloc_size, - PROT_READ|PROT_WRITE, - MAP_ANON|MAP_PRIVATE, 0, 0); + PROT_READ | PROT_WRITE, + MAP_FIXED_NOREPLACE | MAP_ANON | MAP_PRIVATE, + 0, 0); } else { new_alloc_size = 0; mapped_addr = brk_page; @@ -883,12 +878,6 @@ abi_long do_brk(abi_ulong brk_val) target_brk = brk_val; brk_page = new_host_brk_page; return target_brk; - } else if (mapped_addr != -1) { - /* Mapped but at wrong address, meaning there wasn't actually - * enough space for this brk. - */ - target_munmap(mapped_addr, new_alloc_size); - mapped_addr = -1; } #if defined(TARGET_ALPHA)