From: Nicholas Piggin <npiggin@gmail.com>
To: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: libc-alpha@sourceware.org, libc-dev@lists.llvm.org,
linux-api@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Michael Ellerman <mpe@ellerman.id.au>,
Matheus Castanho <msc@linux.ibm.com>,
musl@lists.openwall.com
Subject: [musl] Re: Linux powerpc new system call instruction and ABI
Date: Wed, 19 May 2021 20:59:05 +1000 [thread overview]
Message-ID: <1621421721.r9fefebis8.astroid@bobo.none> (raw)
In-Reply-To: <20210519102403.GA15207@altlinux.org>
Excerpts from Dmitry V. Levin's message of May 19, 2021 8:24 pm:
> On Wed, May 19, 2021 at 12:50:24PM +1000, Nicholas Piggin wrote:
> [...]
>> With this patch, I think the ptrace ABI should mostly be fixed. I think
>> a problem remains with applications that look at system call return
>> registers directly and have powerpc specific error cases. Those probably
>> will just need to be updated unfortunately. Michael thought it might be
>> possible to return an indication via ptrace somehow that the syscall is
>> using a new ABI, so such apps can be updated to test for it. I don't
>> know how that would be done.
>
> Is there any sane way for these applications to handle the scv case?
> How can they tell that the scv semantics is being used for the given
> syscall invocation? Can this information be obtained e.g. from struct
> pt_regs?
Not that I know of. Michael suggested there might be a way to add
something. ptrace_syscall_info has some pad bytes, could
we use one for flags bits and set a bit for "new system call ABI"?
As a more hacky thing you could make a syscall with -1 and see how
the error looks, and then assume all syscalls will be the same.
Thanks,
Nick
>
> For example, in strace we have the following powerpc-specific code used
> for syscall tampering:
>
> $ cat src/linux/powerpc/set_error.c
> /*
> * Copyright (c) 2016-2021 The strace developers.
> * All rights reserved.
> *
> * SPDX-License-Identifier: LGPL-2.1-or-later
> */
>
> static int
> arch_set_r3_ccr(struct tcb *tcp, const unsigned long r3,
> const unsigned long ccr_set, const unsigned long ccr_clear)
> {
> if (ptrace_syscall_info_is_valid() &&
> upeek(tcp, sizeof(long) * PT_CCR, &ppc_regs.ccr))
> return -1;
> const unsigned long old_ccr = ppc_regs.ccr;
> ppc_regs.gpr[3] = r3;
> ppc_regs.ccr |= ccr_set;
> ppc_regs.ccr &= ~ccr_clear;
> if (ppc_regs.ccr != old_ccr &&
> upoke(tcp, sizeof(long) * PT_CCR, ppc_regs.ccr))
> return -1;
> return upoke(tcp, sizeof(long) * (PT_R0 + 3), ppc_regs.gpr[3]);
> }
>
> static int
> arch_set_error(struct tcb *tcp)
> {
> return arch_set_r3_ccr(tcp, tcp->u_error, 0x10000000, 0);
> }
>
> static int
> arch_set_success(struct tcb *tcp)
> {
> return arch_set_r3_ccr(tcp, tcp->u_rval, 0, 0x10000000);
> }
>
>
> --
> ldv
>
next prev parent reply other threads:[~2021-05-19 10:59 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 8:12 [musl] " Nicholas Piggin
2020-06-11 8:12 ` [musl] [PATCH 1/2] powerpc/64s/exception: treat NIA below __end_interrupts as soft-masked Nicholas Piggin
2020-07-24 13:25 ` [musl] " Michael Ellerman
2020-06-11 8:12 ` [musl] [PATCH 2/2] powerpc/64s: system call support for scv/rfscv instructions Nicholas Piggin
2020-07-23 6:47 ` [musl] " Michael Ellerman
2020-07-23 16:48 ` Christophe Leroy
2020-07-24 10:45 ` Michael Ellerman
2020-06-11 21:02 ` [musl] Re: Linux powerpc new system call instruction and ABI Segher Boessenkool
2020-06-14 9:26 ` Nicholas Piggin
2021-05-18 23:13 ` Dmitry V. Levin
2021-05-19 2:50 ` Nicholas Piggin
2021-05-19 5:01 ` Nicholas Piggin
2021-05-21 19:40 ` Matheus Castanho
2021-05-21 19:52 ` Florian Weimer
2021-05-21 20:00 ` Matheus Castanho
2021-05-21 20:52 ` Dmitry V. Levin
2021-05-24 12:11 ` Matheus Castanho
2021-05-24 20:33 ` Matheus Castanho
2021-05-19 10:24 ` Dmitry V. Levin
2021-05-19 10:59 ` Nicholas Piggin [this message]
2021-05-19 12:39 ` Tulio Magno Quites Machado Filho
2021-05-19 13:26 ` Dmitry V. Levin
2021-05-19 22:51 ` Nicholas Piggin
2021-05-19 23:27 ` Dmitry V. Levin
2021-05-20 2:40 ` Nicholas Piggin
2021-05-20 3:06 ` Dmitry V. Levin
2021-05-20 5:12 ` Nicholas Piggin
2021-05-19 7:33 ` Joakim Tjernlund
2021-05-19 7:55 ` Nicholas Piggin
2021-05-19 8:08 ` Joakim Tjernlund
2021-05-19 8:42 ` Nicholas Piggin
2021-05-19 11:12 ` Nicholas Piggin
2021-05-19 14:38 ` Segher Boessenkool
2021-05-19 15:06 ` Joakim Tjernlund
2021-05-19 15:22 ` Segher Boessenkool
2021-05-19 15:36 ` Rich Felker
2021-05-19 18:09 ` Joakim Tjernlund
2021-05-19 23:48 ` Rich Felker
2021-05-20 1:06 ` Dmitry V. Levin
2021-05-20 2:45 ` Nicholas Piggin
2021-05-20 2:59 ` Dmitry V. Levin
2021-05-20 7:20 ` Nicholas Piggin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1621421721.r9fefebis8.astroid@bobo.none \
--to=npiggin@gmail.com \
--cc=ldv@altlinux.org \
--cc=libc-alpha@sourceware.org \
--cc=libc-dev@lists.llvm.org \
--cc=linux-api@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mpe@ellerman.id.au \
--cc=msc@linux.ibm.com \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).