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([71.212.131.115]) by smtp.gmail.com with ESMTPSA id c25-20020aa781d9000000b0068a54866ca8sm1906977pfn.134.2023.08.31.19.23.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Aug 2023 19:23:51 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: laurent@vivier.eu, alex.bennee@linaro.org Subject: [PATCH v2 23/33] linux-user: Split out mmap_h_gt_g Date: Thu, 31 Aug 2023 19:23:21 -0700 Message-Id: <20230901022331.115247-24-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230901022331.115247-1-richard.henderson@linaro.org> References: <20230901022331.115247-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::42f; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42f.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 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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org Signed-off-by: Richard Henderson --- linux-user/mmap.c | 288 ++++++++++++++++++++++------------------------ 1 file changed, 139 insertions(+), 149 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index ed82b4bb75..6ab2f35e6f 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -223,7 +223,16 @@ int target_mprotect(abi_ulong start, abi_ulong len, int target_prot) return ret; } -/* map an incomplete host page */ +/* + * Map an incomplete host page. + * + * Here be dragons. This case will not work if there is an existing + * overlapping host page, which is file mapped, and for which the mapping + * is beyond the end of the file. In that case, we will see SIGBUS when + * trying to write a portion of this page. + * + * FIXME: Work around this with a temporary signal handler and longjmp. + */ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, int prot, int flags, int fd, off_t offset) { @@ -629,19 +638,138 @@ static abi_long mmap_h_lt_g(abi_ulong start, abi_ulong len, int host_prot, return mmap_end(start, last, start, pass_last, mmap_flags, page_flags); } +/* + * Special case host page size > target page size. + * + * The two special cases are address and file offsets that are valid + * for the guest that cannot be directly represented by the host. + */ +static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len, + int target_prot, int host_prot, + int flags, int page_flags, int fd, + off_t offset, int host_page_size) +{ + void *p, *want_p = g2h_untagged(start); + off_t host_offset = offset & -host_page_size; + abi_ulong last, real_start, real_last; + bool misaligned_offset = false; + size_t host_len; + + if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) { + /* + * Adjust the offset to something representable on the host. + */ + host_len = len + offset - host_offset; + p = mmap(want_p, host_len, host_prot, flags, fd, host_offset); + if (p == MAP_FAILED) { + return -1; + } + + /* Update start to the file position at offset. */ + p += offset - host_offset; + + start = h2g(p); + last = start + len - 1; + return mmap_end(start, last, start, last, flags, page_flags); + } + + if (!(flags & MAP_ANONYMOUS)) { + misaligned_offset = (start ^ offset) & (host_page_size - 1); + + /* + * The fallback for misalignment is a private mapping + read. + * This carries none of semantics required of MAP_SHARED. + */ + if (misaligned_offset && (flags & MAP_TYPE) != MAP_PRIVATE) { + errno = EINVAL; + return -1; + } + } + + last = start + len - 1; + real_start = start & -host_page_size; + real_last = ROUND_UP(last, host_page_size) - 1; + + /* + * Handle the start and end of the mapping. + */ + if (real_start < start) { + abi_ulong real_page_last = real_start + host_page_size - 1; + if (last <= real_page_last) { + /* Entire allocation a subset of one host page. */ + if (!mmap_frag(real_start, start, last, target_prot, + flags, fd, offset)) { + return -1; + } + return mmap_end(start, last, -1, 0, flags, page_flags); + } + + if (!mmap_frag(real_start, start, real_page_last, target_prot, + flags, fd, offset)) { + return -1; + } + real_start = real_page_last + 1; + } + + if (last < real_last) { + abi_ulong real_page_start = real_last - host_page_size + 1; + if (!mmap_frag(real_page_start, real_page_start, last, + target_prot, flags, fd, + offset + real_page_start - start)) { + return -1; + } + real_last = real_page_start - 1; + } + + if (real_start > real_last) { + return mmap_end(start, last, -1, 0, flags, page_flags); + } + + /* + * Handle the middle of the mapping. + */ + + host_len = real_last - real_start + 1; + want_p += real_start - start; + + if (flags & MAP_ANONYMOUS) { + p = mmap(want_p, host_len, host_prot, flags, -1, 0); + } else if (!misaligned_offset) { + p = mmap(want_p, host_len, host_prot, flags, fd, + offset + real_start - start); + } else { + p = mmap(want_p, host_len, host_prot | PROT_WRITE, + flags | MAP_ANONYMOUS, -1, 0); + } + if (p != want_p) { + if (p != MAP_FAILED) { + munmap(p, host_len); + errno = EEXIST; + } + return -1; + } + + if (misaligned_offset) { + /* TODO: The read could be short. */ + if (pread(fd, p, host_len, offset + real_start - start) != host_len) { + munmap(p, host_len); + return -1; + } + if (!(host_prot & PROT_WRITE)) { + mprotect(p, host_len, host_prot); + } + } + + return mmap_end(start, last, -1, 0, flags, page_flags); +} + static abi_long target_mmap__locked(abi_ulong start, abi_ulong len, int target_prot, int flags, int page_flags, int fd, off_t offset) { int host_page_size = qemu_real_host_page_size(); - abi_ulong ret, last, real_start, real_last, retaddr, host_len; - abi_ulong passthrough_start = -1, passthrough_last = 0; - off_t host_offset; int host_prot; - real_start = start & -host_page_size; - host_offset = offset & -host_page_size; - /* * For reserved_va, we are in full control of the allocation. * Find a suitible hole and convert to MAP_FIXED. @@ -655,6 +783,8 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len, } flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED; } else if (!(flags & MAP_FIXED)) { + abi_ulong real_start = start & -host_page_size; + off_t host_offset = offset & -host_page_size; size_t real_len = len + offset - host_offset; abi_ulong align = MAX(host_page_size, TARGET_PAGE_SIZE); @@ -676,150 +806,10 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len, } else if (host_page_size < TARGET_PAGE_SIZE) { return mmap_h_lt_g(start, len, host_prot, flags, page_flags, fd, offset, host_page_size); - } - - if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) { - uintptr_t host_start; - void *p; - - host_len = len + offset - host_offset; - host_len = ROUND_UP(host_len, host_page_size); - - /* Note: we prefer to control the mapping address. */ - p = mmap(g2h_untagged(start), host_len, host_prot, - flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0); - if (p == MAP_FAILED) { - return -1; - } - /* update start so that it points to the file position at 'offset' */ - host_start = (uintptr_t)p; - if (!(flags & MAP_ANONYMOUS)) { - p = mmap(g2h_untagged(start), len, host_prot, - flags | MAP_FIXED, fd, host_offset); - if (p == MAP_FAILED) { - munmap(g2h_untagged(start), host_len); - return -1; - } - host_start += offset - host_offset; - } - start = h2g(host_start); - last = start + len - 1; - passthrough_start = start; - passthrough_last = last; } else { - last = start + len - 1; - real_last = ROUND_UP(last, host_page_size) - 1; - - if (flags & MAP_FIXED_NOREPLACE) { - /* Validate that the chosen range is empty. */ - if (!page_check_range_empty(start, last)) { - errno = EEXIST; - return -1; - } - - /* - * With reserved_va, the entire address space is mmaped in the - * host to ensure it isn't accidentally used for something else. - * We have just checked that the guest address is not mapped - * within the guest, but need to replace the host reservation. - * - * Without reserved_va, despite the guest address check above, - * keep MAP_FIXED_NOREPLACE so that the guest does not overwrite - * any host address mappings. - */ - if (reserved_va) { - flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED; - } - } - - /* - * worst case: we cannot map the file because the offset is not - * aligned, so we read it - */ - if (!(flags & MAP_ANONYMOUS) && - (offset & (host_page_size - 1)) != (start & (host_page_size - 1))) { - /* - * msync() won't work here, so we return an error if write is - * possible while it is a shared mapping - */ - if ((flags & MAP_TYPE) == MAP_SHARED - && (target_prot & PROT_WRITE)) { - errno = EINVAL; - return -1; - } - retaddr = target_mmap(start, len, target_prot | PROT_WRITE, - (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE)) - | MAP_PRIVATE | MAP_ANONYMOUS, - -1, 0); - if (retaddr == -1) { - return -1; - } - if (pread(fd, g2h_untagged(start), len, offset) == -1) { - return -1; - } - if (!(target_prot & PROT_WRITE)) { - ret = target_mprotect(start, len, target_prot); - assert(ret == 0); - } - return mmap_end(start, last, -1, 0, flags, page_flags); - } - - /* handle the start of the mapping */ - if (start > real_start) { - if (real_last == real_start + host_page_size - 1) { - /* one single host page */ - if (!mmap_frag(real_start, start, last, - target_prot, flags, fd, offset)) { - return -1; - } - return mmap_end(start, last, -1, 0, flags, page_flags); - } - if (!mmap_frag(real_start, start, - real_start + host_page_size - 1, - target_prot, flags, fd, offset)) { - return -1; - } - real_start += host_page_size; - } - /* handle the end of the mapping */ - if (last < real_last) { - abi_ulong real_page = real_last - host_page_size + 1; - if (!mmap_frag(real_page, real_page, last, - target_prot, flags, fd, - offset + real_page - start)) { - return -1; - } - real_last -= host_page_size; - } - - /* map the middle (easier) */ - if (real_start < real_last) { - void *p, *want_p; - off_t offset1; - size_t len1; - - if (flags & MAP_ANONYMOUS) { - offset1 = 0; - } else { - offset1 = offset + real_start - start; - } - len1 = real_last - real_start + 1; - want_p = g2h_untagged(real_start); - - p = mmap(want_p, len1, host_prot, flags, fd, offset1); - if (p != want_p) { - if (p != MAP_FAILED) { - munmap(p, len1); - errno = EEXIST; - } - return -1; - } - passthrough_start = real_start; - passthrough_last = real_last; - } + return mmap_h_gt_g(start, len, target_prot, host_prot, flags, + page_flags, fd, offset, host_page_size); } - return mmap_end(start, last, passthrough_start, passthrough_last, - flags, page_flags); } /* NOTE: all the constants are the HOST ones */