From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46173) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eM5A4-0001Pe-Uq for qemu-devel@nongnu.org; Mon, 04 Dec 2017 23:48:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eM5A1-00026C-OH for qemu-devel@nongnu.org; Mon, 04 Dec 2017 23:48:53 -0500 Received: from mail-pf0-x244.google.com ([2607:f8b0:400e:c00::244]:37617) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1eM5A1-00025V-Eu for qemu-devel@nongnu.org; Mon, 04 Dec 2017 23:48:49 -0500 Received: by mail-pf0-x244.google.com with SMTP id n6so10338947pfa.4 for ; Mon, 04 Dec 2017 20:48:49 -0800 (PST) From: Richard Henderson Date: Mon, 4 Dec 2017 20:48:44 -0800 Message-Id: <20171205044844.3597-1-richard.henderson@linaro.org> Subject: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, Richard Henderson From: Richard Henderson If the interp_prefix is a complete chroot, it may have a *lot* of files. Setting up the cache for this is quite expensive. Instead, use the *at versions of various syscalls to attempt the operation in the prefix. Signed-off-by: Richard Henderson --- Changes since v1 (Nov 2016): * Require interp_dirfd set before trying the *at path. r~ --- linux-user/qemu.h | 1 + linux-user/elfload.c | 12 ++- linux-user/main.c | 3 +- linux-user/syscall.c | 236 ++++++++++++++++++++++++++++++++++++++++++--------- 4 files changed, 208 insertions(+), 44 deletions(-) diff --git a/linux-user/qemu.h b/linux-user/qemu.h index 4edd7d0c08..d04924fd2e 100644 --- a/linux-user/qemu.h +++ b/linux-user/qemu.h @@ -437,6 +437,7 @@ void mmap_fork_start(void); void mmap_fork_end(int child); /* main.c */ +extern int interp_dirfd; extern unsigned long guest_stack_size; /* user access */ diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 20f3d8c2c3..5d3f7aa11d 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2203,7 +2203,17 @@ static void load_elf_interp(const char *filename, struct image_info *info, { int fd, retval; - fd = open(path(filename), O_RDONLY); + switch (interp_dirfd > 0 && filename[0] == '/') { + case true: + fd = openat(interp_dirfd, filename + 1, O_RDONLY); + if (fd >= 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + fd = open(filename, O_RDONLY); + break; + } if (fd < 0) { goto exit_perror; } diff --git a/linux-user/main.c b/linux-user/main.c index 6286661bd3..06edc2c6bc 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -99,6 +99,7 @@ unsigned long reserved_va; static void usage(int exitcode); static const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX; +int interp_dirfd; const char *qemu_uname_release; /* XXX: on x86 MAP_GROWSDOWN only works if ESP <= address + 32, so @@ -4297,7 +4298,7 @@ int main(int argc, char **argv, char **envp) memset(&bprm, 0, sizeof (bprm)); /* Scan interp_prefix dir for replacement files. */ - init_paths(interp_prefix); + interp_dirfd = open(interp_prefix, O_CLOEXEC | O_DIRECTORY | O_PATH); init_qemu_uname_release(); diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 11c9116c4a..dc4387e3e6 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -7228,7 +7228,18 @@ static abi_long do_name_to_handle_at(abi_long dirfd, abi_long pathname, fh = g_malloc0(total_size); fh->handle_bytes = size; - ret = get_errno(name_to_handle_at(dirfd, path(name), fh, &mid, flags)); + switch (interp_dirfd > 0 && name[0] == '/') { + case true: + ret = name_to_handle_at(interp_dirfd, name + 1, fh, &mid, flags); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = name_to_handle_at(dirfd, name, fh, &mid, flags); + break; + } + ret = get_errno(ret); unlock_user(name, pathname, 0); /* man name_to_handle_at(2): @@ -7604,6 +7615,7 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags, #endif { NULL, NULL, NULL } }; + int ret; if (is_proc_myself(pathname, "exe")) { int execfd = qemu_getauxval(AT_EXECFD); @@ -7643,7 +7655,18 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags, return fd; } - return safe_openat(dirfd, path(pathname), flags, mode); + switch (interp_dirfd > 0 && pathname[0] == '/') { + case true: + ret = safe_openat(interp_dirfd, pathname + 1, flags, mode); + if (ret >= 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = safe_openat(dirfd, pathname, flags, mode); + break; + } + return ret; } #define TIMER_MAGIC 0x0caf0000 @@ -7729,6 +7752,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, struct stat st; struct statfs stfs; void *p; + char *fn; #if defined(DEBUG_ERESTARTSYS) /* Debug-only code for exercising the syscall-restart code paths @@ -8260,10 +8284,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, } else { tvp = NULL; } - if (!(p = lock_user_string(arg2))) + if (!(fn = lock_user_string(arg2))) goto efault; - ret = get_errno(futimesat(arg1, path(p), tvp)); - unlock_user(p, arg2, 0); + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = futimesat(interp_dirfd, fn + 1, tvp); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = futimesat(arg1, fn, tvp); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg2, 0); } break; #endif @@ -8277,18 +8312,42 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, #endif #ifdef TARGET_NR_access case TARGET_NR_access: - if (!(p = lock_user_string(arg1))) + if (!(fn = lock_user_string(arg1))) { goto efault; - ret = get_errno(access(path(p), arg2)); - unlock_user(p, arg1, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = faccessat(interp_dirfd, fn + 1, arg2, 0); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = access(fn, arg2); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg1, 0); break; #endif #if defined(TARGET_NR_faccessat) && defined(__NR_faccessat) case TARGET_NR_faccessat: - if (!(p = lock_user_string(arg2))) + if (!(fn = lock_user_string(arg2))) { goto efault; - ret = get_errno(faccessat(arg1, p, arg3, 0)); - unlock_user(p, arg2, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = faccessat(interp_dirfd, fn + 1, arg3, 0); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = faccessat(arg1, fn, arg3, 0); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg2, 0); break; #endif #ifdef TARGET_NR_nice /* not on alpha */ @@ -8415,7 +8474,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, } else { if (!(p = lock_user_string(arg1))) goto efault; - ret = get_errno(acct(path(p))); + ret = get_errno(acct(p)); unlock_user(p, arg1, 0); } break; @@ -9181,14 +9240,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, case TARGET_NR_readlink: { void *p2; - p = lock_user_string(arg1); + fn = lock_user_string(arg1); p2 = lock_user(VERIFY_WRITE, arg2, arg3, 0); - if (!p || !p2) { + if (!fn || !p2) { ret = -TARGET_EFAULT; } else if (!arg3) { /* Short circuit this for the magic exe check. */ ret = -TARGET_EINVAL; - } else if (is_proc_myself((const char *)p, "exe")) { + } else if (is_proc_myself(fn, "exe")) { char real[PATH_MAX], *temp; temp = realpath(exec_path, real); /* Return value is # of bytes that we wrote to the buffer. */ @@ -9202,10 +9261,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, memcpy(p2, real, ret); } } else { - ret = get_errno(readlink(path(p), p2, arg3)); + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = readlinkat(interp_dirfd, fn + 1, p2, arg3); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = readlink(fn, p2, arg3); + break; + } + ret = get_errno(ret); } unlock_user(p2, arg2, ret); - unlock_user(p, arg1, 0); + unlock_user(fn, arg1, 0); } break; #endif @@ -9213,20 +9283,31 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, case TARGET_NR_readlinkat: { void *p2; - p = lock_user_string(arg2); + fn = lock_user_string(arg2); p2 = lock_user(VERIFY_WRITE, arg3, arg4, 0); - if (!p || !p2) { + if (!fn || !p2) { ret = -TARGET_EFAULT; - } else if (is_proc_myself((const char *)p, "exe")) { + } else if (is_proc_myself(fn, "exe")) { char real[PATH_MAX], *temp; temp = realpath(exec_path, real); ret = temp == NULL ? get_errno(-1) : strlen(real) ; snprintf((char *)p2, arg4, "%s", real); } else { - ret = get_errno(readlinkat(arg1, path(p), p2, arg4)); + switch (interp_dirfd && fn[0] == '/') { + case true: + ret = readlinkat(interp_dirfd, fn + 1, p2, arg4); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = readlinkat(arg1, fn, p2, arg4); + break; + } + ret = get_errno(ret); } unlock_user(p2, arg3, ret); - unlock_user(p, arg2, 0); + unlock_user(fn, arg2, 0); } break; #endif @@ -9395,7 +9476,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, case TARGET_NR_statfs: if (!(p = lock_user_string(arg1))) goto efault; - ret = get_errno(statfs(path(p), &stfs)); + ret = get_errno(statfs(p, &stfs)); unlock_user(p, arg1, 0); convert_statfs: if (!is_error(ret)) { @@ -9425,7 +9506,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, case TARGET_NR_statfs64: if (!(p = lock_user_string(arg1))) goto efault; - ret = get_errno(statfs(path(p), &stfs)); + ret = get_errno(statfs(p, &stfs)); unlock_user(p, arg1, 0); convert_statfs64: if (!is_error(ret)) { @@ -9654,18 +9735,42 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, break; #ifdef TARGET_NR_stat case TARGET_NR_stat: - if (!(p = lock_user_string(arg1))) + if (!(fn = lock_user_string(arg1))) { goto efault; - ret = get_errno(stat(path(p), &st)); - unlock_user(p, arg1, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = fstatat(interp_dirfd, fn + 1, &st, 0); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = stat(fn, &st); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg1, 0); goto do_stat; #endif #ifdef TARGET_NR_lstat case TARGET_NR_lstat: - if (!(p = lock_user_string(arg1))) + if (!(fn = lock_user_string(arg1))) { goto efault; - ret = get_errno(lstat(path(p), &st)); - unlock_user(p, arg1, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = fstatat(interp_dirfd, fn + 1, &st, AT_SYMLINK_NOFOLLOW); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = lstat(fn, &st); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg1, 0); goto do_stat; #endif case TARGET_NR_fstat: @@ -10745,20 +10850,44 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, #endif #ifdef TARGET_NR_stat64 case TARGET_NR_stat64: - if (!(p = lock_user_string(arg1))) + if (!(fn = lock_user_string(arg1))) { goto efault; - ret = get_errno(stat(path(p), &st)); - unlock_user(p, arg1, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = fstatat(interp_dirfd, fn + 1, &st, 0); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = stat(fn, &st); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg1, 0); if (!is_error(ret)) ret = host_to_target_stat64(cpu_env, arg2, &st); break; #endif #ifdef TARGET_NR_lstat64 case TARGET_NR_lstat64: - if (!(p = lock_user_string(arg1))) + if (!(fn = lock_user_string(arg1))) { goto efault; - ret = get_errno(lstat(path(p), &st)); - unlock_user(p, arg1, 0); + } + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = fstatat(interp_dirfd, fn + 1, &st, AT_SYMLINK_NOFOLLOW); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = lstat(fn, &st); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg1, 0); if (!is_error(ret)) ret = host_to_target_stat64(cpu_env, arg2, &st); break; @@ -10777,9 +10906,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, #ifdef TARGET_NR_newfstatat case TARGET_NR_newfstatat: #endif - if (!(p = lock_user_string(arg2))) + if (!(fn = lock_user_string(arg2))) goto efault; - ret = get_errno(fstatat(arg1, path(p), &st, arg4)); + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = fstatat(interp_dirfd, fn + 1, &st, arg4); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = fstatat(arg1, fn, &st, arg4); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg2, 0); if (!is_error(ret)) ret = host_to_target_stat64(cpu_env, arg3, &st); break; @@ -11776,12 +11917,23 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, if (!arg2) ret = get_errno(sys_utimensat(arg1, NULL, tsp, arg4)); else { - if (!(p = lock_user_string(arg2))) { + if (!(fn = lock_user_string(arg2))) { ret = -TARGET_EFAULT; goto fail; } - ret = get_errno(sys_utimensat(arg1, path(p), tsp, arg4)); - unlock_user(p, arg2, 0); + switch (interp_dirfd > 0 && fn[0] == '/') { + case true: + ret = sys_utimensat(interp_dirfd, fn + 1, tsp, arg4); + if (ret == 0 || errno != ENOENT) { + break; + } + /* fallthru */ + default: + ret = sys_utimensat(arg1, fn, tsp, arg4); + break; + } + ret = get_errno(ret); + unlock_user(fn, arg2, 0); } } break; @@ -11811,7 +11963,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, #if defined(TARGET_NR_inotify_add_watch) && defined(__NR_inotify_add_watch) case TARGET_NR_inotify_add_watch: p = lock_user_string(arg2); - ret = get_errno(sys_inotify_add_watch(arg1, path(p), arg3)); + ret = get_errno(sys_inotify_add_watch(arg1, p, arg3)); unlock_user(p, arg2, 0); break; #endif -- 2.13.6