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: 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 >
WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com> To: "Dmitry V. Levin" <ldv@altlinux.org> Cc: libc-alpha@sourceware.org, Matheus Castanho <msc@linux.ibm.com>, musl@lists.openwall.com, linux-api@vger.kernel.org, libc-dev@lists.llvm.org, linuxppc-dev@lists.ozlabs.org Subject: 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: 83+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-11 8:12 Linux powerpc new system call instruction and ABI Nicholas Piggin 2020-06-11 8:12 ` Nicholas Piggin 2020-06-11 8:12 ` [PATCH 1/2] powerpc/64s/exception: treat NIA below __end_interrupts as soft-masked Nicholas Piggin 2020-06-11 8:12 ` Nicholas Piggin 2020-07-24 13:25 ` Michael Ellerman 2020-07-24 13:25 ` Michael Ellerman 2020-06-11 8:12 ` [PATCH 2/2] powerpc/64s: system call support for scv/rfscv instructions Nicholas Piggin 2020-06-11 8:12 ` Nicholas Piggin 2020-07-23 6:47 ` Michael Ellerman 2020-07-23 16:48 ` Christophe Leroy 2020-07-23 16:48 ` Christophe Leroy 2020-07-24 10:45 ` Michael Ellerman 2020-07-24 10:45 ` Michael Ellerman 2020-06-11 21:02 ` Linux powerpc new system call instruction and ABI Segher Boessenkool 2020-06-11 21:02 ` Segher Boessenkool 2020-06-14 9:26 ` Nicholas Piggin 2020-06-14 9:26 ` Nicholas Piggin 2021-05-18 23:13 ` Dmitry V. Levin 2021-05-18 23:13 ` Dmitry V. Levin 2021-05-19 2:50 ` Nicholas Piggin 2021-05-19 2:50 ` Nicholas Piggin 2021-05-19 5:01 ` Nicholas Piggin 2021-05-19 5:01 ` Nicholas Piggin 2021-05-21 19:40 ` Matheus Castanho 2021-05-21 19:40 ` Matheus Castanho 2021-05-21 19:52 ` Florian Weimer 2021-05-21 19:52 ` Florian Weimer 2021-05-21 20:00 ` Matheus Castanho 2021-05-21 20:00 ` Matheus Castanho 2021-05-21 20:52 ` Dmitry V. Levin 2021-05-21 20:52 ` Dmitry V. Levin 2021-05-24 12:11 ` Matheus Castanho 2021-05-24 12:11 ` Matheus Castanho 2021-05-24 20:33 ` Matheus Castanho 2021-05-24 20:33 ` Matheus Castanho 2021-05-19 10:24 ` Dmitry V. Levin 2021-05-19 10:24 ` Dmitry V. Levin 2021-05-19 10:59 ` Nicholas Piggin [this message] 2021-05-19 10:59 ` Nicholas Piggin 2021-05-19 12:39 ` Tulio Magno Quites Machado Filho 2021-05-19 12:39 ` Tulio Magno Quites Machado Filho 2021-05-19 13:26 ` Dmitry V. Levin 2021-05-19 13:26 ` Dmitry V. Levin 2021-05-19 22:51 ` Nicholas Piggin 2021-05-19 22:51 ` Nicholas Piggin 2021-05-19 23:27 ` Dmitry V. Levin 2021-05-19 23:27 ` Dmitry V. Levin 2021-05-20 2:40 ` Nicholas Piggin 2021-05-20 2:40 ` Nicholas Piggin 2021-05-20 3:06 ` Dmitry V. Levin 2021-05-20 3:06 ` Dmitry V. Levin 2021-05-20 5:12 ` Nicholas Piggin 2021-05-20 5:12 ` Nicholas Piggin 2021-05-19 7:33 ` Joakim Tjernlund 2021-05-19 7:33 ` Joakim Tjernlund 2021-05-19 7:55 ` Nicholas Piggin 2021-05-19 7:55 ` Nicholas Piggin 2021-05-19 8:08 ` Joakim Tjernlund 2021-05-19 8:08 ` Joakim Tjernlund 2021-05-19 8:42 ` Nicholas Piggin 2021-05-19 8:42 ` Nicholas Piggin 2021-05-19 11:12 ` Nicholas Piggin 2021-05-19 11:12 ` Nicholas Piggin 2021-05-19 14:38 ` Segher Boessenkool 2021-05-19 14:38 ` Segher Boessenkool 2021-05-19 15:06 ` Joakim Tjernlund 2021-05-19 15:06 ` Joakim Tjernlund 2021-05-19 15:22 ` Segher Boessenkool 2021-05-19 15:22 ` Segher Boessenkool 2021-05-19 15:36 ` [musl] " Rich Felker 2021-05-19 15:36 ` Rich Felker 2021-05-19 18:09 ` Joakim Tjernlund 2021-05-19 18:09 ` Joakim Tjernlund 2021-05-19 23:48 ` [musl] " Rich Felker 2021-05-19 23:48 ` Rich Felker 2021-05-20 1:06 ` Dmitry V. Levin 2021-05-20 1:06 ` Dmitry V. Levin 2021-05-20 2:45 ` Nicholas Piggin 2021-05-20 2:45 ` Nicholas Piggin 2021-05-20 2:59 ` Dmitry V. Levin 2021-05-20 2:59 ` Dmitry V. Levin 2021-05-20 7:20 ` Nicholas Piggin 2021-05-20 7:20 ` Nicholas Piggin
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