From patchwork Wed Jul 31 18:31:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella Netto X-Patchwork-Id: 1139965 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=sourceware.org (client-ip=209.132.180.131; helo=sourceware.org; envelope-from=libc-alpha-return-104073-incoming=patchwork.ozlabs.org@sourceware.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.b="bTu5AHGO"; dkim=pass (2048-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b="r7B77di0"; dkim-atps=neutral Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45zMTN4sS6z9s00 for ; Thu, 1 Aug 2019 04:31:52 +1000 (AEST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:subject:date:message-id; q=dns; s= default; b=pWIW867zJVy+WmZO5lcHqQoQBhpSMP4uxJNg2/R79LEqUH8AM4x8j w1U46G5vRc5mtbO0dDmVom4NplJ5NGnRiAVhxEv024JbVcwqzXZG9WHqNtVBzhyF 1Gf/GM3XjgfbifQV6+gAJ2TwclJtLCdJR6suAMFyyyY+hiFCyZ9T70= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:subject:date:message-id; s=default; bh=UOFESxQPEbJRJzak1ffKHuePnVo=; b=bTu5AHGOvzS3hnDVB2aKvDIfWuRI iqQqiSzu9QVrtGVtnUcLSa4p/rxAXKRC1aNjMFdh8HPOUloZyUAhBmZvcYqs016J kjJo3fy4oQf+7JVm62gyzAQg/lUkFtda0bn6FzeJPaLeEcNoCibw6/msLz7bItXB mESYkmEadGy0gow= Received: (qmail 122212 invoked by alias); 31 Jul 2019 18:31:45 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 122204 invoked by uid 89); 31 Jul 2019 18:31:44 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-15.8 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.1 spammy=offsetof, Our X-HELO: mail-qt1-f196.google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:subject:date:message-id; bh=uujKKiaFQSuV6+tEBdmXKlpITJ6uszb/OBs3WzZXiEU=; b=r7B77di0zkdgNvPkidszJW5/Hcm7ICMCZ40/00t/TVIgdqw+/txdjLrE2sOr6Kk4bX aMNCwYX4ylgCDMvJIu2yBXX8FsxhVObBq50tqdLPTEKZb8F9aOWbF+GmNPbzqgwasnc2 Ti1b7pjgM3rG4XYBA+BIJ1Thnu75p+2INdv5LON1btoHnd8T0BDC9pPLPzFRlck03iM5 2A+aNlHmdvTaKfqNINb1igwEfTjAD4N/FadkUk0PiFw1ea7BySCIlXjcphQ4Yb/NSOuE Ws/r4VRrRu8Q2Umpb6sgnBg4RfSEIJz7LpHKMEiuiDl+nNib/Fl72uhVpJk/OTjG9v1I B+cg== From: Adhemerval Zanella To: libc-alpha@sourceware.org Subject: [PATCH v2 1/5] mips: Do not malloc on getdents64 fallback Date: Wed, 31 Jul 2019 15:31:32 -0300 Message-Id: <20190731183136.21545-1-adhemerval.zanella@linaro.org> This patch changes how the fallback getdents64 implementation calls non-LFS getdents by replacing the scratch_buffer with static buffer plus a loop on getdents calls. This avoids the potential malloc call on scratch_buffer_set_array_size for large input buffer size at the cost of more getdents syscalls. It also adds a small optimization for older kernels, where the first ENOSYS failure for getdents64 disable subsequent calls. Check the dirent tests on a mips64-linux-gnu with getdents64 code disabled. * sysdeps/unix/sysv/linux/mips/mips64/getdents64.c (__getdents64): Add small optimization for older kernel to avoid issuing __NR_getdents64 on each call and replace scratch_buffer usage with a static allocated buffer. --- .../unix/sysv/linux/mips/mips64/getdents64.c | 122 ++++++++---------- 1 file changed, 54 insertions(+), 68 deletions(-) diff --git a/sysdeps/unix/sysv/linux/mips/mips64/getdents64.c b/sysdeps/unix/sysv/linux/mips/mips64/getdents64.c index 8bf3abb0e0..3b5afd9324 100644 --- a/sysdeps/unix/sysv/linux/mips/mips64/getdents64.c +++ b/sysdeps/unix/sysv/linux/mips/mips64/getdents64.c @@ -22,98 +22,84 @@ #include #include #include -#include #include ssize_t -__getdents64 (int fd, void *buf0, size_t nbytes) +__getdents64 (int fd, void *buf, size_t nbytes) { - char *buf = buf0; - /* The system call takes an unsigned int argument, and some length checks in the kernel use an int type. */ if (nbytes > INT_MAX) nbytes = INT_MAX; #ifdef __NR_getdents64 - ssize_t ret = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes); - if (ret != -1) - return ret; + static bool getdents64_supportted = true; + if (atomic_load_relaxed (&getdents64_supportted)) + { + ssize_t ret = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes); + if (ret >= 0 || errno != ENOSYS) + return ret; + + atomic_store_relaxed (&getdents64_supportted, false); + } #endif /* Unfortunately getdents64 was only wire-up for MIPS n64 on Linux 3.10. - If syscall is not available it need to fallback to non-LFS one. */ + If the syscall is not available it need to fallback to the non-LFS one. + Also to avoid an unbounded allocation through VLA/alloca or malloc (which + would make the syscall non async-signal-safe) it uses a limited buffer. + This is sub-optimal for large NBYTES, however this is a fallback + mechanism to emulate a syscall that kernel should provide. */ + enum { KBUF_SIZE = 1024 }; struct kernel_dirent - { - unsigned long d_ino; - unsigned long d_off; - unsigned short int d_reclen; - char d_name[256]; - }; - - const size_t size_diff = (offsetof (struct dirent64, d_name) - - offsetof (struct kernel_dirent, d_name)); - - size_t red_nbytes = MIN (nbytes - - ((nbytes / (offsetof (struct dirent64, d_name) - + 14)) * size_diff), - nbytes - size_diff); - - struct scratch_buffer tmpbuf; - scratch_buffer_init (&tmpbuf); - if (!scratch_buffer_set_array_size (&tmpbuf, red_nbytes, sizeof (uint8_t))) - INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOMEM); - - struct kernel_dirent *skdp, *kdp; - skdp = kdp = tmpbuf.data; - - ssize_t retval = INLINE_SYSCALL_CALL (getdents, fd, kdp, red_nbytes); - if (retval == -1) - { - scratch_buffer_free (&tmpbuf); - return -1; - } + { + unsigned long d_ino; + unsigned long d_off; + unsigned short int d_reclen; + char d_name[1]; + } kbuf[KBUF_SIZE / sizeof (struct kernel_dirent)]; + size_t kbuf_size = nbytes < KBUF_SIZE ? nbytes : KBUF_SIZE; - off64_t last_offset = -1; struct dirent64 *dp = (struct dirent64 *) buf; - while ((char *) kdp < (char *) skdp + retval) + + size_t nb = 0; + off64_t last_offset = -1; + + ssize_t r; + while ((r = INLINE_SYSCALL_CALL (getdents, fd, kbuf, kbuf_size)) > 0) { - const size_t alignment = _Alignof (struct dirent64); - /* Since kdp->d_reclen is already aligned for the kernel structure - this may compute a value that is bigger than necessary. */ - size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1) - & ~(alignment - 1)); - if ((char *) dp + new_reclen > buf + nbytes) - { - /* Our heuristic failed. We read too many entries. Reset - the stream. */ - assert (last_offset != -1); - __lseek64 (fd, last_offset, SEEK_SET); - - if ((char *) dp == buf) + struct kernel_dirent *skdp, *kdp; + skdp = kdp = kbuf; + + while ((char *) kdp < (char *) skdp + r) + { + const size_t alignment = _Alignof (struct dirent64); + size_t new_reclen = ((kdp->d_reclen + alignment - 1) + & ~(alignment - 1)); + if (nb + new_reclen > nbytes) { - scratch_buffer_free (&tmpbuf); - return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL); + /* The new entry will overflow the input buffer, rewind to + last obtained entry and return. */ + __lseek64 (fd, last_offset, SEEK_SET); + goto out; } + nb += new_reclen; - break; - } - - last_offset = kdp->d_off; - dp->d_ino = kdp->d_ino; - dp->d_off = kdp->d_off; - dp->d_reclen = new_reclen; - dp->d_type = *((char *) kdp + kdp->d_reclen - 1); - memcpy (dp->d_name, kdp->d_name, - kdp->d_reclen - offsetof (struct kernel_dirent, d_name)); + dp->d_ino = kdp->d_ino; + dp->d_off = last_offset = kdp->d_off; + dp->d_reclen = new_reclen; + dp->d_type = *((char *) kdp + kdp->d_reclen - 1); + memcpy (dp->d_name, kdp->d_name, + kdp->d_reclen - offsetof (struct kernel_dirent, d_name)); - dp = (struct dirent64 *) ((char *) dp + new_reclen); - kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen); + dp = (struct dirent64 *) ((char *) dp + new_reclen); + kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen); + } } - scratch_buffer_free (&tmpbuf); - return (char *) dp - buf; +out: + return (char *) dp - (char *) buf; } libc_hidden_def (__getdents64) weak_alias (__getdents64, getdents64)