git: bdf0f24bb16d - main - linux: implement PTRACE_GET_SYSCALL_INFO

Jessica Clarke jrtc27 at freebsd.org
Tue Sep 14 22:54:17 UTC 2021


On 14 Sep 2021, at 23:45, Konstantin Belousov <kostikbel at gmail.com> wrote:
> 
> On Tue, Sep 14, 2021 at 08:41:06PM +0000, Edward Tomasz Napierala wrote:
>> The branch main has been updated by trasz:
>> 
>> URL: https://cgit.FreeBSD.org/src/commit/?id=bdf0f24bb16d556a5b1e01cdfc087d08e91ac572
>> 
>> commit bdf0f24bb16d556a5b1e01cdfc087d08e91ac572
>> Author:     Edward Tomasz Napierala <trasz at FreeBSD.org>
>> AuthorDate: 2021-09-12 11:31:10 +0000
>> Commit:     Edward Tomasz Napierala <trasz at FreeBSD.org>
>> CommitDate: 2021-09-14 20:19:55 +0000
>> 
>>    linux: implement PTRACE_GET_SYSCALL_INFO
>> 
>>    This is one of the pieces required to make modern (ie Focal)
>>    strace(1) work.
>> 
>>    Reviewed By:    jhb (earlier version)
>>    Sponsored by:   EPSRC
>>    Differential Revision:  https://reviews.freebsd.org/D28212
>> ---
>> lib/libsysdecode/mktables             |  2 +-
>> sys/amd64/linux/linux_ptrace.c        | 98 +++++++++++++++++++++++++++++++++--
>> sys/compat/freebsd32/freebsd32_misc.c |  3 ++
>> sys/kern/sys_process.c                | 17 ++++++
>> sys/sys/ptrace.h                      |  4 ++
>> 5 files changed, 120 insertions(+), 4 deletions(-)
>> 
>> +	case PT_GET_SC_ARGS_ALL:
>> +		CTR1(KTR_PTRACE, "PT_GET_SC_ARGS_ALL: pid %d", p->p_pid);
>> +		if ((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) == 0
>> +#ifdef COMPAT_FREEBSD32
>> +		    || (wrap32 && !safe)
>> +#endif
>> +		    ) {
>> +			error = EINVAL;
>> +			break;
>> +		}
>> +		bcopy(td2->td_sa.args, addr, sizeof(td2->td_sa.args));
>> +		break;
> 
> This is awful, you already got that feedback in review, as I read it.
> I strongly suggest to remove PT_GET_SC_ARGS_ALL, and instead checks something
> in the implementation of PT_GET_SC_ARGS to select either full copy or just
> nargs args.
> 
> Easiest thing for 'something' would be SV_PROC_ABI(p) == SV_ABI_LINUX.

That is incorrect. The original review just changed PT_GET_SC_ARGS even
for FreeBSD and that was what was described as horrible. John suggested
two alternatives: this approach, and having the Linuxulator bypass
kern_ptrace entirely by doing its own thing.

Your option seems simpler but I don’t know if there’s a good reason why
that wasn’t suggested.

Jess



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