From nobody Sun Oct 26 00:03:05 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1521643204749814.501003391514; Wed, 21 Mar 2018 07:40:04 -0700 (PDT) Received: from localhost ([::1]:55487 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eyeuB-0005De-R2 for importer@patchew.org; Wed, 21 Mar 2018 10:39:55 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36763) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eyesU-0003qe-JC for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:38:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eyesQ-00017x-CW for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:38:10 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:56750 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eyesQ-00017e-6x for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:38:06 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E6C08401DEBF; Wed, 21 Mar 2018 14:38:03 +0000 (UTC) Received: from localhost (ovpn-112-73.ams2.redhat.com [10.36.112.73]) by smtp.corp.redhat.com (Postfix) with ESMTP id 636AE10B009A; Wed, 21 Mar 2018 14:38:03 +0000 (UTC) From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= To: qemu-devel@nongnu.org Date: Wed, 21 Mar 2018 15:37:53 +0100 Message-Id: <20180321143754.5606-2-marcandre.lureau@redhat.com> In-Reply-To: <20180321143754.5606-1-marcandre.lureau@redhat.com> References: <20180321143754.5606-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 21 Mar 2018 14:38:03 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 21 Mar 2018 14:38:03 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'marcandre.lureau@redhat.com' RCPT:'' Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PULL 1/2] dump.c: allow fd_write_vmcore to return errno on failure X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Henrique Barboza , peter.maydell@linaro.org, Jose Ricardo Ziviani , Yasmin Beatriz , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Type: text/plain; charset="utf-8" From: Yasmin Beatriz fd_write_vmcore can fail to execute for a lot of reasons that can be retrieved by errno, but it only returns -1. This makes difficult for the caller to know what happened and only a generic error message is propagated back to the user. This is an example using dump-guest-memory: (qemu) dump-guest-memory /home/yasmin/mnt/test.dump dump: failed to save memory All callers of fd_write_vmcore of dump.c does error handling via error_setg(), so at first it seems feasible to add the Error pointer as an argument of fd_write_vmcore. This proved to be more complex than it first looked. fd_write_vmcore is used by write_elf64_notes and write_elf32_notes as a WriteCoreDumpFunction prototype. WriteCoreDumpFuncti= on is declared in include/qom/cpu.h and is used all around the code. This leaves us with few alternatives: - change the WriteCoreDumpFunction prototype to include an error pointer. This would require to change all functions that implements this prototype to also receive an Error pointer; - change both write_elf64_notes and write_elf32_notes to no use the WriteCoreDumpFunction. These functions use not only fd_write_vmcore but also buf_write_note, so this would require to change buf_write_note to handle an Error pointer. Considerable easier than the alternative above, but it's still a lot of code just for the benefit of the callers of fd_write_vmcore. This patch presents an easier solution that benefits all fd_write_vmcore callers: - instead of returning -1 on error, return -errno. All existing callers already checks for ret < 0 so there is no need to change the caller's logic too much. This also allows the retrieval of the errno. - all callers were updated to use error_setg_errno instead of just errno_setg. Now that fd_write_vmcore can return an errno, let's update all callers so they can benefit from a more detailed error message. This is the same dump-guest-memory example with this patch applied: (qemu) dump-guest-memory /home/yasmin/mnt/test.dump dump: failed to save memory: No space left on device (qemu) This example illustrates an error of fd_write_vmcore when called from write_data. All other callers will benefit from better error messages as well. Reported-by: yilzhang@redhat.com Cc: Jose Ricardo Ziviani Signed-off-by: Yasmin Beatriz Signed-off-by: Daniel Henrique Barboza Message-Id: <20180212142506.28445-2-danielhb@linux.vnet.ibm.com> Reviewed-by: Eric Blake Reviewed-by: Marc-Andr=C3=A9 Lureau Signed-off-by: Marc-Andr=C3=A9 Lureau --- dump.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/dump.c b/dump.c index 6bdb0dbe23..669f715274 100644 --- a/dump.c +++ b/dump.c @@ -107,7 +107,7 @@ static int fd_write_vmcore(const void *buf, size_t size= , void *opaque) =20 written_size =3D qemu_write_full(s->fd, buf, size); if (written_size !=3D size) { - return -1; + return -errno; } =20 return 0; @@ -140,7 +140,7 @@ static void write_elf64_header(DumpState *s, Error **er= rp) =20 ret =3D fd_write_vmcore(&elf_header, sizeof(elf_header), s); if (ret < 0) { - error_setg(errp, "dump: failed to write elf header"); + error_setg_errno(errp, -ret, "dump: failed to write elf header"); } } =20 @@ -171,7 +171,7 @@ static void write_elf32_header(DumpState *s, Error **er= rp) =20 ret =3D fd_write_vmcore(&elf_header, sizeof(elf_header), s); if (ret < 0) { - error_setg(errp, "dump: failed to write elf header"); + error_setg_errno(errp, -ret, "dump: failed to write elf header"); } } =20 @@ -194,7 +194,8 @@ static void write_elf64_load(DumpState *s, MemoryMappin= g *memory_mapping, =20 ret =3D fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s); if (ret < 0) { - error_setg(errp, "dump: failed to write program header table"); + error_setg_errno(errp, -ret, + "dump: failed to write program header table"); } } =20 @@ -217,7 +218,8 @@ static void write_elf32_load(DumpState *s, MemoryMappin= g *memory_mapping, =20 ret =3D fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s); if (ret < 0) { - error_setg(errp, "dump: failed to write program header table"); + error_setg_errno(errp, -ret, + "dump: failed to write program header table"); } } =20 @@ -237,7 +239,8 @@ static void write_elf64_note(DumpState *s, Error **errp) =20 ret =3D fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s); if (ret < 0) { - error_setg(errp, "dump: failed to write program header table"); + error_setg_errno(errp, -ret, + "dump: failed to write program header table"); } } =20 @@ -302,7 +305,8 @@ static void write_elf32_note(DumpState *s, Error **errp) =20 ret =3D fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s); if (ret < 0) { - error_setg(errp, "dump: failed to write program header table"); + error_setg_errno(errp, -ret, + "dump: failed to write program header table"); } } =20 @@ -355,7 +359,8 @@ static void write_elf_section(DumpState *s, int type, E= rror **errp) =20 ret =3D fd_write_vmcore(&shdr, shdr_size, s); if (ret < 0) { - error_setg(errp, "dump: failed to write section header table"); + error_setg_errno(errp, -ret, + "dump: failed to write section header table"); } } =20 @@ -365,7 +370,7 @@ static void write_data(DumpState *s, void *buf, int len= gth, Error **errp) =20 ret =3D fd_write_vmcore(buf, length, s); if (ret < 0) { - error_setg(errp, "dump: failed to save memory"); + error_setg_errno(errp, -ret, "dump: failed to save memory"); } else { s->written_size +=3D length; } --=20 2.16.2.521.g9aa15f885a