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Fri, 30 Jun 2023 06:22:10 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: mjt@tls.msk.ru, laurent@vivier.eu Subject: [PATCH 13/24] linux-user: Rewrite mmap_frag Date: Fri, 30 Jun 2023 15:21:48 +0200 Message-Id: <20230630132159.376995-14-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230630132159.376995-1-richard.henderson@linaro.org> References: <20230630132159.376995-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::335; envelope-from=richard.henderson@linaro.org; helo=mail-wm1-x335.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=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1688131668701100006 Content-Type: text/plain; charset="utf-8" Use 'last' variables instead of 'end' variables. Always zero MAP_ANONYMOUS fragments, which we previously failed to do if they were not writable; early exit in case we allocate a new page from the kernel, known zeros. Signed-off-by: Richard Henderson --- linux-user/mmap.c | 123 +++++++++++++++++++++++----------------------- 1 file changed, 62 insertions(+), 61 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index c9bd72d3f9..e332555dd2 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -221,73 +221,76 @@ int target_mprotect(abi_ulong start, abi_ulong len, i= nt target_prot) } =20 /* map an incomplete host page */ -static int mmap_frag(abi_ulong real_start, - abi_ulong start, abi_ulong end, - int prot, int flags, int fd, off_t offset) +static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong las= t, + int prot, int flags, int fd, off_t offset) { - abi_ulong real_end, addr; + abi_ulong real_last; void *host_start; - int prot1, prot_new; + int prot_old, prot_new; + int host_prot_old, host_prot_new; =20 - real_end =3D real_start + qemu_host_page_size; - host_start =3D g2h_untagged(real_start); - - /* get the protection of the target pages outside the mapping */ - prot1 =3D 0; - for (addr =3D real_start; addr < real_end; addr++) { - if (addr < start || addr >=3D end) { - prot1 |=3D page_get_flags(addr); - } + if (!(flags & MAP_ANONYMOUS) + && (flags & MAP_TYPE) =3D=3D MAP_SHARED + && (prot & PROT_WRITE)) { + /* + * msync() won't work with the partial page, so we return an + * error if write is possible while it is a shared mapping. + */ + errno =3D EINVAL; + return false; } =20 - if (prot1 =3D=3D 0) { - /* no page was there, so we allocate one */ + real_last =3D real_start + qemu_host_page_size - 1; + host_start =3D g2h_untagged(real_start); + + /* Get the protection of the target pages outside the mapping. */ + prot_old =3D 0; + for (abi_ulong a =3D real_start; a < start; a +=3D TARGET_PAGE_SIZE) { + prot_old |=3D page_get_flags(a); + } + for (abi_ulong a =3D real_last; a > last; a -=3D TARGET_PAGE_SIZE) { + prot_old |=3D page_get_flags(a); + } + + if (prot_old =3D=3D 0) { + /* + * Since !(prot_old & PAGE_VALID), there were no guest pages + * outside of the fragment we need to map. Allocate a new host + * page to cover, discarding whatever else may have been present. + */ void *p =3D mmap(host_start, qemu_host_page_size, target_to_host_prot(prot), flags | MAP_ANONYMOUS, -1, 0); if (p =3D=3D MAP_FAILED) { - return -1; + return false; } - prot1 =3D prot; + prot_old =3D prot; } - prot1 &=3D PAGE_BITS; + prot_new =3D prot | prot_old; =20 - prot_new =3D prot | prot1; - if (!(flags & MAP_ANONYMOUS)) { - /* - * msync() won't work here, so we return an error if write is - * possible while it is a shared mapping. - */ - if ((flags & MAP_TYPE) =3D=3D MAP_SHARED && (prot & PROT_WRITE)) { - return -1; - } + host_prot_old =3D target_to_host_prot(prot_old); + host_prot_new =3D target_to_host_prot(prot_new); =20 - /* adjust protection to be able to read */ - if (!(prot1 & PROT_WRITE)) { - mprotect(host_start, qemu_host_page_size, - target_to_host_prot(prot1) | PROT_WRITE); - } + /* Adjust protection to be able to write. */ + if (!(host_prot_old & PROT_WRITE)) { + host_prot_old |=3D PROT_WRITE; + mprotect(host_start, qemu_host_page_size, host_prot_old); + } =20 - /* read the corresponding file data */ - if (pread(fd, g2h_untagged(start), end - start, offset) =3D=3D -1)= { - return -1; - } - - /* put final protection */ - if (prot_new !=3D (prot1 | PROT_WRITE)) { - mprotect(host_start, qemu_host_page_size, - target_to_host_prot(prot_new)); - } + /* Read or zero the new guest pages. */ + if (flags & MAP_ANONYMOUS) { + memset(g2h_untagged(start), 0, last - start + 1); } else { - if (prot_new !=3D prot1) { - mprotect(host_start, qemu_host_page_size, - target_to_host_prot(prot_new)); - } - if (prot_new & PROT_WRITE) { - memset(g2h_untagged(start), 0, end - start); + if (pread(fd, g2h_untagged(start), last - start + 1, offset) =3D= =3D -1) { + return false; } } - return 0; + + /* Put final protection */ + if (host_prot_new !=3D host_prot_old) { + mprotect(host_start, qemu_host_page_size, host_prot_new); + } + return true; } =20 #if HOST_LONG_BITS =3D=3D 64 && TARGET_ABI_BITS =3D=3D 64 @@ -675,27 +678,25 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, = int target_prot, if (start > real_start) { if (real_end =3D=3D real_start + qemu_host_page_size) { /* one single host page */ - ret =3D mmap_frag(real_start, start, end, - target_prot, flags, fd, offset); - if (ret =3D=3D -1) { + if (!mmap_frag(real_start, start, end - 1, + target_prot, flags, fd, offset)) { goto fail; } goto the_end1; } - ret =3D mmap_frag(real_start, start, real_start + qemu_host_pa= ge_size, - target_prot, flags, fd, offset); - if (ret =3D=3D -1) { + if (!mmap_frag(real_start, start, + real_start + qemu_host_page_size - 1, + target_prot, flags, fd, offset)) { goto fail; } real_start +=3D qemu_host_page_size; } /* handle the end of the mapping */ if (end < real_end) { - ret =3D mmap_frag(real_end - qemu_host_page_size, - real_end - qemu_host_page_size, end, - target_prot, flags, fd, - offset + real_end - qemu_host_page_size - star= t); - if (ret =3D=3D -1) { + if (!mmap_frag(real_end - qemu_host_page_size, + real_end - qemu_host_page_size, end - 1, + target_prot, flags, fd, + offset + real_end - qemu_host_page_size - start= )) { goto fail; } real_end -=3D qemu_host_page_size; --=20 2.34.1