From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37530) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fDiQt-0004r0-TL for qemu-devel@nongnu.org; Tue, 01 May 2018 23:27:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fDiQq-0006fs-O2 for qemu-devel@nongnu.org; Tue, 01 May 2018 23:27:55 -0400 Received: from mail-pg0-x241.google.com ([2607:f8b0:400e:c05::241]:44797) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fDiQq-0006eg-Bi for qemu-devel@nongnu.org; Tue, 01 May 2018 23:27:52 -0400 Received: by mail-pg0-x241.google.com with SMTP id 82-v6so9589800pge.11 for ; Tue, 01 May 2018 20:27:52 -0700 (PDT) References: <20180501235332.31245-1-laurent@vivier.eu> From: Richard Henderson Message-ID: <573362f2-a00c-0bf6-59e2-6dd4aa143e16@linaro.org> Date: Tue, 1 May 2018 20:27:46 -0700 MIME-Version: 1.0 In-Reply-To: <20180501235332.31245-1-laurent@vivier.eu> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] linux-user: remove useless padding in flock64 structure List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laurent Vivier , qemu-devel@nongnu.org Cc: Riku Voipio On 05/01/2018 04:53 PM, Laurent Vivier wrote: > Since commit 8efb2ed5ec ("linux-user: Correct signedness of > target_flock l_start and l_len fields"), flock64 structure uses > abi_llong for l_start and l_len in place of "unsigned long long" > this should force them to be aligned accordingly to the target > rules. So we can remove the padding field and the QEMU_PACKED > attribute. > > I have compared the result of the following program before and > after the change: > > cat -> flock64_dump < p/d sizeof(struct target_flock64) > p/d &((struct target_flock64 *)0)->l_type > p/d &((struct target_flock64 *)0)->l_whence > p/d &((struct target_flock64 *)0)->l_start > p/d &((struct target_flock64 *)0)->l_len > p/d &((struct target_flock64 *)0)->l_pid > quit > EOF > > for file in build/all/*-linux-user/qemu-* ; do > echo $file > gdb -batch -nx -x flock64_dump $file 2> /dev/null > done > > The sizeof() changes because we remove the QEMU_PACKED. > The new size is 32 (except for i386 and m68k) and this is > the real size of "struct flock64" on the target architecture. > > The following architectures differ: > aarch64_be, aarch64, alpha, armeb, arm, cris, hppa, nios2, or1k, > riscv32, riscv64, s390x. > > For a subset of these architectures, I have checked with the following > program the new structure is the correct one: > > #include > #define __USE_LARGEFILE64 > #include > > int main(void) > { > printf("struct flock64 %d\n", sizeof(struct flock64)); > printf("l_type %d\n", &((struct flock64 *)0)->l_type); > printf("l_whence %d\n", &((struct flock64 *)0)->l_whence); > printf("l_start %d\n", &((struct flock64 *)0)->l_start); > printf("l_len %d\n", &((struct flock64 *)0)->l_len); > printf("l_pid %d\n", &((struct flock64 *)0)->l_pid); > } > > [I have checked aarch64, alpha, arm, s390x] > > I have also fixed the alignment value for sh4 (to align llong on 4 bytes) > (see c2e3dee6e0 "linux-user: Define target alignment size") Reviewed-by: Richard Henderson r~