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[79.214.176.215]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a8989035f80sm87313166b.78.2024.08.29.07.45.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2024 07:45:24 -0700 (PDT) From: Michael Vogt X-Google-Original-From: Michael Vogt To: qemu-devel@nongnu.org Cc: Richard Henderson , Laurent Vivier , Michael Vogt Subject: [PATCH v2 1/1] linux-user: add openat2 support in linux-user Date: Thu, 29 Aug 2024 16:44:15 +0200 Message-ID: <20240829144413.6942-4-mvogt@redhat.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240829144413.6942-2-mvogt@redhat.com> References: <20240829144413.6942-2-mvogt@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::52a; envelope-from=michael.vogt@gmail.com; helo=mail-ed1-x52a.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, FREEMAIL_FROM=0.001, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org This commit adds support for the `openat2()` syscall in the `linux-user` userspace emulator. It is implemented by extracting a new helper `maybe_do_fake_open()` out of the exiting `do_guest_openat()` and share that with the new `do_guest_openat2()`. Unfortunatly we cannot just make do_guest_openat2() a superset of do_guest_openat() because the openat2() syscall is stricter with the argument checking and will return an error for invalid flags or mode combinations (which open()/openat() will ignore). Note that in this commit using openat2() for a "faked" file in /proc will ignore the "resolve" flags. This is not great but it seems similar to the exiting behavior when openat() is called with a dirfd to "/proc". Here too the fake file lookup may not catch the special file because "realpath()" is used to determine if the path is in /proc. Alternatively to ignoring we could simply fail with `-TARGET_ENOSYS` (or similar) if `resolve` flags are passed and we found something that looks like a file in /proc that needs faking. Signed-off-by: Michael Vogt Buglink: https://github.com/osbuild/bootc-image-builder/issues/619 --- linux-user/syscall.c | 98 +++++++++++++++++++++++++++++++++++++-- linux-user/syscall_defs.h | 7 +++ meson.build | 1 + 3 files changed, 102 insertions(+), 4 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 9d5415674d..c241c6d3a0 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -85,6 +85,10 @@ #include #endif +#ifdef HAVE_OPENAT2_H +#include +#endif + #define termios host_termios #define winsize host_winsize #define termio host_termio @@ -653,6 +657,10 @@ safe_syscall3(ssize_t, read, int, fd, void *, buff, size_t, count) safe_syscall3(ssize_t, write, int, fd, const void *, buff, size_t, count) safe_syscall4(int, openat, int, dirfd, const char *, pathname, \ int, flags, mode_t, mode) +#ifdef HAVE_OPENAT2_H +safe_syscall4(int, openat2, int, dirfd, const char *, pathname, \ + const struct open_how *, how, size_t, size) +#endif #if defined(TARGET_NR_wait4) || defined(TARGET_NR_waitpid) safe_syscall4(pid_t, wait4, pid_t, pid, int *, status, int, options, \ struct rusage *, rusage) @@ -8334,8 +8342,9 @@ static int open_net_route(CPUArchState *cpu_env, int fd) } #endif -int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname, - int flags, mode_t mode, bool safe) +static int maybe_do_fake_open(CPUArchState *cpu_env, int dirfd, + const char *fname, int flags, mode_t mode, + bool safe, bool *use_returned_fd) { g_autofree char *proc_name = NULL; const char *pathname; @@ -8362,6 +8371,7 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname, #endif { NULL, NULL, NULL } }; + *use_returned_fd = true; /* if this is a file from /proc/ filesystem, expand full name */ proc_name = realpath(fname, NULL); @@ -8418,12 +8428,87 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname, return fd; } + *use_returned_fd = false; + return -1; +} + +int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname, + int flags, mode_t mode, bool safe) +{ + bool use_returned_fd; + int fd = maybe_do_fake_open(cpu_env, dirfd, fname, flags, mode, safe, + &use_returned_fd); + if (use_returned_fd) + return fd; + if (safe) { - return safe_openat(dirfd, path(pathname), flags, mode); + return safe_openat(dirfd, path(fname), flags, mode); } else { - return openat(dirfd, path(pathname), flags, mode); + return openat(dirfd, path(fname), flags, mode); + } +} + +#ifdef HAVE_OPENAT2_H +static int do_guest_openat2(CPUArchState *cpu_env, int dirfd, const char *fname, + struct open_how *how) +{ + /* + * Ideally we would pass "how->resolve" flags into this helper too but + * the lookup for files that need faking is based on "realpath()" so + * neither a dirfd for "proc" nor restrictions via "resolve" flags can + * be honored right now. + */ + bool use_returned_fd; + int fd = maybe_do_fake_open(cpu_env, dirfd, fname, how->flags, how->mode, + true, &use_returned_fd); + if (use_returned_fd) + return fd; + + return safe_openat2(dirfd, fname, how, sizeof(struct open_how)); +} + +static int do_openat2(CPUArchState *cpu_env, abi_long arg1, abi_long arg2, + abi_long arg3, abi_long arg4) +{ + struct open_how how = {0}; + struct target_open_how *target_how = NULL; + int ret; + + char *p = lock_user_string(arg2); + if (!p) { + ret = -TARGET_EFAULT; + goto out; + } + if (!(lock_user_struct(VERIFY_READ, target_how, arg3, 1))) { + ret = -TARGET_EFAULT; + goto out; + } + size_t target_open_how_struct_size = arg4; + if (target_open_how_struct_size < sizeof(struct target_open_how)) { + ret = -TARGET_EINVAL; + goto out; + } + if (target_open_how_struct_size > sizeof(struct target_open_how)) { + qemu_log_mask(LOG_UNIMP, "Unimplemented openat2 open_how size: %lu\n", + target_open_how_struct_size); + ret = -TARGET_E2BIG; + goto out; } + + how.flags = target_to_host_bitmask(target_how->flags, fcntl_flags_tbl); + how.mode = tswap64(target_how->mode); + how.resolve = tswap64(target_how->resolve); + ret = get_errno(do_guest_openat2(cpu_env, arg1, p, &how)); + + fd_trans_unregister(ret); + out: + if (target_how) + unlock_user_struct(target_how, arg3, 0); + if (p) + unlock_user(p, arg2, 0); + return ret; } +#endif ssize_t do_guest_readlink(const char *pathname, char *buf, size_t bufsiz) { @@ -9197,6 +9282,11 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, fd_trans_unregister(ret); unlock_user(p, arg2, 0); return ret; +#if defined(TARGET_NR_openat2) && defined(HAVE_OPENAT2_H) + case TARGET_NR_openat2: + ret = do_openat2(cpu_env, arg1, arg2, arg3, arg4); + return ret; +#endif #if defined(TARGET_NR_name_to_handle_at) && defined(CONFIG_OPEN_BY_HANDLE) case TARGET_NR_name_to_handle_at: ret = do_name_to_handle_at(arg1, arg2, arg3, arg4, arg5); diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h index a00b617cae..2a79ae13c9 100644 --- a/linux-user/syscall_defs.h +++ b/linux-user/syscall_defs.h @@ -2754,4 +2754,11 @@ struct target_sched_param { abi_int sched_priority; }; +/* from kernel's include/uapi/linux/openat2.h */ +struct target_open_how { + abi_ullong flags; + abi_ullong mode; + abi_ullong resolve; +}; + #endif diff --git a/meson.build b/meson.build index fbda17c987..220ccbcbe6 100644 --- a/meson.build +++ b/meson.build @@ -2465,6 +2465,7 @@ config_host_data.set('CONFIG_LINUX_MAGIC_H', cc.has_header('linux/magic.h')) config_host_data.set('CONFIG_VALGRIND_H', cc.has_header('valgrind/valgrind.h')) config_host_data.set('HAVE_BTRFS_H', cc.has_header('linux/btrfs.h')) config_host_data.set('HAVE_DRM_H', cc.has_header('libdrm/drm.h')) +config_host_data.set('HAVE_OPENAT2_H', cc.has_header('linux/openat2.h')) config_host_data.set('HAVE_PTY_H', cc.has_header('pty.h')) config_host_data.set('HAVE_SYS_DISK_H', cc.has_header('sys/disk.h')) config_host_data.set('HAVE_SYS_IOCCOM_H', cc.has_header('sys/ioccom.h'))