From: Oleg Nesterov <oleg@redhat.com>
To: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: Andy Lutomirski <luto@kernel.org>,
Elvira Khabirova <lineprinter@altlinux.org>,
Eugene Syromyatnikov <esyr@redhat.com>,
Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
linux-api@vger.kernel.org, strace-devel@lists.strace.io,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 24/25] ptrace: add PTRACE_GET_SYSCALL_INFO request
Date: Wed, 12 Dec 2018 19:00:17 +0100 [thread overview]
Message-ID: <20181212180017.GB30309@redhat.com> (raw)
In-Reply-To: <20181211202709.GA3839@altlinux.org>
On 12/11, Dmitry V. Levin wrote:
>
> > > Still can't understand... are you saying that without (say) __pad2[4]
> > > sizeof(ptrace_syscall_info) or offsetofend(ptrace_syscall_info, seccomp)
> > > will depend on arch? Or what? I am just curious.
> >
> > Yes, without padding these sizes will depend on architecture:
>
> > $ cat t.c
> > #include <linux/types.h>
> > int main() {
> > struct s {
> > __u64 nr;
> > __u64 args[6];
> > __u32 ret_data;
> > };
> > return sizeof(struct s);
> > }
> >
> > $ gcc -m64 -Wall -O2 t.c && ./a.out; echo $?
> > 64
> > $ gcc -m32 -Wall -O2 t.c && ./a.out; echo $?
> > 60
> >
> > This happens because __u64 has 32-bit alignment on some 32-bit
> > architectures like x86.
> >
> > There is also m68k where __u32 has 16-bit alignment.
OK, thanks,
> Said that, I think it would be better if PTRACE_GET_SYSCALL_INFO
> did not take these trailing pads into account, e.g.
>
> - return offsetofend(struct ptrace_syscall_info, seccomp);
> + return offsetofend(struct ptrace_syscall_info, seccomp.ret_data);
> ...
> - return offsetofend(struct ptrace_syscall_info, exit);
> + return offsetofend(struct ptrace_syscall_info, exit.is_error);
>
> The reason is that it would allow to fill these trailing pads with
> something useful in the future.
Agreed.
But this way everything looks even more confusing. To me it would be
better to simply remove these pads, but I won't insist.
Oleg.
next prev parent reply other threads:[~2018-12-12 18:00 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20181210042352.GA6092@altlinux.org>
2018-12-10 4:27 ` [PATCH v5 01/25] alpha: define remaining syscall_get_* functions Dmitry V. Levin
2018-12-10 4:28 ` [PATCH v5 02/25] Move EM_ARCOMPACT and EM_ARCV2 to uapi/linux/elf-em.h Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 03/25] arc: define syscall_get_arch() Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 04/25] c6x: " Dmitry V. Levin
2018-12-11 22:40 ` Mark Salter
2018-12-10 4:29 ` [PATCH v5 05/25] elf-em.h: add EM_CSKY Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 06/25] csky: define syscall_get_arch() Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 07/25] h8300: define remaining syscall_get_* functions Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 08/25] Move EM_HEXAGON to uapi/linux/elf-em.h Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 09/25] hexagon: define remaining syscall_get_* functions Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 10/25] Move EM_NDS32 to uapi/linux/elf-em.h Dmitry V. Levin
2018-12-10 4:29 ` [PATCH v5 11/25] nds32: define syscall_get_arch() Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 12/25] nios2: " Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 13/25] m68k: add asm/syscall.h Dmitry V. Levin
2018-12-10 8:45 ` Geert Uytterhoeven
2018-12-10 12:40 ` Dmitry V. Levin
2018-12-10 13:06 ` Geert Uytterhoeven
2018-12-10 13:30 ` Dmitry V. Levin
2018-12-12 8:55 ` Dmitry V. Levin
2018-12-12 9:01 ` Geert Uytterhoeven
2018-12-12 9:27 ` Dmitry V. Levin
2018-12-12 9:43 ` Geert Uytterhoeven
2018-12-12 12:04 ` Dmitry V. Levin
2018-12-12 12:27 ` Geert Uytterhoeven
2018-12-12 12:37 ` Dmitry V. Levin
2018-12-12 12:54 ` Geert Uytterhoeven
2018-12-12 13:07 ` Dmitry V. Levin
2018-12-12 23:12 ` Dmitry V. Levin
2019-03-29 22:04 ` Dmitry V. Levin
2019-03-30 20:57 ` Geert Uytterhoeven
2018-12-10 4:30 ` [PATCH v5 14/25] mips: define syscall_get_error() Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 15/25] parisc: " Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 16/25] powerpc: " Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 17/25] riscv: define syscall_get_arch() Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 18/25] Move EM_XTENSA to uapi/linux/elf-em.h Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 19/25] xtensa: define syscall_get_* functions Dmitry V. Levin
2018-12-10 5:02 ` Max Filippov
2018-12-10 12:53 ` Dmitry V. Levin
2018-12-10 20:14 ` Max Filippov
2018-12-10 20:24 ` Dmitry V. Levin
2018-12-10 20:30 ` Dmitry V. Levin
2018-12-10 21:29 ` Max Filippov
2018-12-12 10:45 ` kbuild test robot
2018-12-19 5:58 ` kbuild test robot
2018-12-10 4:30 ` [PATCH v5 20/25] Move EM_UNICORE to uapi/linux/elf-em.h Dmitry V. Levin
2018-12-10 4:30 ` [PATCH v5 21/25] unicore32: add asm/syscall.h Dmitry V. Levin
2018-12-10 4:31 ` [PATCH v5 22/25] syscall_get_arch: add "struct task_struct *" argument Dmitry V. Levin
2018-12-10 17:29 ` Kees Cook
2018-12-11 22:44 ` Mark Salter
2018-12-10 4:31 ` [PATCH v5 23/25] powerpc/ptrace: replace ptrace_report_syscall() with a tracehook call Dmitry V. Levin
2018-12-10 4:31 ` [PATCH v5 24/25] ptrace: add PTRACE_GET_SYSCALL_INFO request Dmitry V. Levin
2018-12-10 14:11 ` Oleg Nesterov
2018-12-10 16:21 ` Dmitry V. Levin
2018-12-11 15:29 ` Oleg Nesterov
2018-12-11 16:23 ` Dmitry V. Levin
2018-12-11 20:27 ` Dmitry V. Levin
2018-12-12 18:00 ` Oleg Nesterov [this message]
2018-12-10 14:26 ` kbuild test robot
2018-12-10 16:09 ` Dmitry V. Levin
2018-12-10 18:04 ` Paul Burton
2018-12-10 21:04 ` Palmer Dabbelt
2018-12-10 19:38 ` Andy Lutomirski
2018-12-10 17:44 ` Kees Cook
2018-12-12 9:28 ` kbuild test robot
2018-12-10 4:31 ` [PATCH v5 25/25] selftests/ptrace: add a test case for PTRACE_GET_SYSCALL_INFO Dmitry V. Levin
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