Re: [PATCH] Implement 'catch syscall' for gdbserver

[Eli Zaretskii <eliz at gnu dot org>]

> From: Josh Stone <jistone@redhat.com>
> Cc: sergiodj@redhat.com, palves@redhat.com, philippe.waroquiers@skynet.be,        Josh Stone <jistone@redhat.com>
> Date: Thu, 29 Oct 2015 18:52:26 -0700
> 
> gdb/ChangeLog:
> 
> 2015-10-29  Josh Stone  <jistone@redhat.com>
> 
> 	* NEWS (Changes since GDB 7.10): Mention QCatchSyscalls and new
> 	GDBserver support for catch syscall.
> 	* remote.c (PACKET_QCatchSyscalls): New enum.
> 	(remote_set_syscall_catchpoint): New function.
> 	(remote_protocol_features): New element for QCatchSyscalls.
> 	(remote_parse_stop_reply): Parse syscall_entry/return stops.
> 	(init_remote_ops): Install remote_set_syscall_catchpoint.
> 	(_initialize_remote): Config QCatchSyscalls.
> 
> gdb/doc/ChangeLog:
> 
> 2015-10-29  Josh Stone  <jistone@redhat.com>
> 
> 	* gdb.texinfo (Remote Configuration): List the QCatchSyscalls packet.
> 	(Stop Reply Packets): List the syscall entry and return stop reasons.
> 	(General Query Packets): Describe QCatchSyscalls, and add it to the
> 	table and detailed list of stub features.
> 
> gdb/gdbserver/ChangeLog:
> 
> 2015-10-29  Josh Stone  <jistone@redhat.com>
> 
> 	* inferiors.h: Include "gdb_vecs.h".
> 	(struct process_info): Add syscalls_to_catch.
> 	* inferiors.c (remove_process): Free syscalls_to_catch.
> 	* remote-utils.c (prepare_resume_reply): Report syscall_entry and
> 	syscall_resume stops.
> 	* server.h (UNKNOWN_SYSCALL, ANY_SYSCALL): Define.
> 	* server.c (handle_general_set): Handle QCatchSyscalls.
> 	(handle_query): Report support for QCatchSyscalls.
> 	* target.h (struct target_ops): Add supports_catch_syscall.
> 	(target_supports_catch_syscall): New macro.
> 	* linux-low.h (struct linux_target_ops): Add get_syscall_trapinfo.
> 	(struct lwp_info): Add syscall_state.
> 	* linux-low.c (SYSCALL_SIGTRAP): Define.
> 	(handle_extended_wait): Mark syscall_state like an entry.
> 	(get_syscall_trapinfo): New function, proxy to the_low_target.
> 	(linux_low_ptrace_options): Enable PTRACE_O_TRACESYSGOOD.
> 	(linux_low_filter_event): Set ptrace options even before arch-specific
> 	setup.  Either toggle syscall_state entry/return or set ignored.
> 	(gdb_catching_syscalls_p): New function.
> 	(gdb_catch_this_syscall_p): New function.
> 	(linux_wait_1): Handle SYSCALL_SIGTRAP.
> 	(linux_resume_one_lwp_throw): Add PTRACE_SYSCALL possibility.
> 	(linux_supports_catch_syscall): New function.
> 	(linux_target_ops): Install it.
> 	* linux-x86-low.c (x86_get_syscall_trapinfo): New function.
> 	(the_low_target): Install it.
> 	* nto-low.c (nto_target_ops): Install NULL supports_catch_syscall.
> 	* spu-low.c (spu_target_ops): Likewise.
> 	* win32-low.c (win32_target_ops): Likewise.
> 
> gdb/testsuite/ChangeLog:
> 
> 2015-10-29  Josh Stone  <jistone@redhat.com>
> 
> 	* gdb.base/catch-syscall.exp: Enable testing for x86 and x86_64 linux
> 	remote targets.
> 	(do_syscall_tests): Only test mid-vfork on local or extended-remote.

The documentation parts are OK, with this minor comment and one
question.  Here's the comment:

> +Note that if a syscall not member of the list is reported, @value{GDBN}
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"a syscall not in the list" sounds simpler and more clear, and doesn't
change the meaning.

> +will filter it if this syscall is not caught.  It is however more efficient
> +to only report the needed syscalls.

The question is about the same sentence: maybe because I don't really
use this stuff, I'm not sure I understand the distinction between
"reported" and "caught" here: what does it mean for a syscall to be
reported, but not caught?  Perhaps this text should be clarified to
not cause such confusion.

Thanks.