svn commit: r350017 - in head: lib/libc/sys sys/kern sys/sys tests/sys/kern

[John Baldwin]

On 11/25/19 11:01 AM, Kyle Evans wrote:
> On Mon, Jul 15, 2019 at 4:48 PM John Baldwin <jhb at freebsd.org> wrote:
>>
>> Author: jhb
>> Date: Mon Jul 15 21:48:02 2019
>> New Revision: 350017
>> URL: https://svnweb.freebsd.org/changeset/base/350017
>>
>> Log:
>>   Add ptrace op PT_GET_SC_RET.
>>
>>   This ptrace operation returns a structure containing the error and
>>   return values from the current system call.  It is only valid when a
>>   thread is stopped during a system call exit (PL_FLAG_SCX is set).
>>
>>   The sr_error member holds the error value from the system call.  Note
>>   that this error value is the native FreeBSD error value that has _not_
>>   been translated to an ABI-specific error value similar to the values
>>   logged to ktrace.
>>
>>   If sr_error is zero, then the return values of the system call will be
>>   set in sr_retval[0] and sr_retval[1].
>>
>>   Reviewed by:  kib
>>   MFC after:    1 month
>>   Sponsored by: DARPA
>>   Differential Revision:        https://reviews.freebsd.org/D20901
>>
>> Modified:
>>   head/lib/libc/sys/ptrace.2
>>   head/sys/kern/sys_process.c
>>   head/sys/sys/ptrace.h
>>   head/tests/sys/kern/ptrace_test.c
>>
> 
> Hey John,
> 
> Any objection to MFC'ing this to stable/12 at least? I've found this
> to be almost-required in the ptrace user I've been working on
> lately... I certainly ripped out plenty of hair before realizing that
> it wasn't detecting error returns properly.

Hmm, I did have it in my queue, but not the most urgent priority.   Are
you using truss or something else?  You can achieve the same thing without
the new op, it just requires arch-specific code to fetch the error status
and return value from registers.

-- 
John Baldwin