I recently stumbled on this code mentioning Linux kernel 2.6.25, and
thought it could be time for some spring cleaning (newer GDBs probably
don't need to supports 12-year old kernels). I then found that the
"legacy" case is probably broken anyway, which gives an even better
motivation for its removal.
In short, this patch removes the configure checks that check if
user_regs_struct contains the fs_base/gs_base fields and adjusts all
uses of the HAVE_STRUCT_USER_REGS_STRUCT_{FS,GS}_BASE macros. The
longer explanation/rationale follows.
Apparently, Linux kernels since 2.6.25 (that's from 2008) have been
reliably providing fs_base and gs_base as part of user_regs_struct.
Commit df5d438e33d7 in the Linux kernel [1] seems related. This means
that we can get these values by reading registers with PTRACE_GETREGS.
Previously, these values were obtained using a separate
PTRACE_ARCH_PRCTL ptrace call.
First, I'm not even sure the configure check was really right in the
first place.
The user_regs_struct used by GDB comes from
/usr/include/x86_64-linux-gnu/sys/user.h (or equivalent on other
distros) and is provided by glibc. glibc has had the fs_base/gs_base
fields in there for a very long time, at least since this commit from
2001 [2]. The Linux kernel also has its version of user_regs_struct,
which I think was exported to user-space at some point. It included the
fs_base/gs_base fields since at least this 2002 commit [3]. In any
case, my conclusion is that the fields were there long before the
aforementioned Linux kernel commit. The kernel commit didn't add these
fields, it only made sure that they have reliable values when obtained
with PTRACE_GETREGS.
So, checking for the presence of the fs_base/gs_base fields in struct
user_regs_struct doesn't sound like a good way of knowing if we can
reliably get the fs_base/gs_base values from PTRACE_GETREGS. My guess
is that if we were using that strategy on a < 2.6.25 kernel, things
would not work correctly:
- configure would find that the user_regs_struct has the fs_base/gs_base
fields (which are probided by glibc anyway)
- we would be reading the fs_base/gs_base values using PTRACE_GETREGS,
for which the kernel would provide unreliable values
Second, I have tried to see how things worked by forcing GDB to not use
fs_base/gs_base from PTRACE_GETREGS (forcing it to use the "legacy"
code, by configuring with
ac_cv_member_struct_user_regs_struct_gs_base=no ac_cv_member_struct_user_regs_struct_fs_base=no
Doing so breaks writing registers back to the inferior. For example,
calling an inferior functions gives an internal error:
(gdb) p malloc(10)
/home/smarchi/src/binutils-gdb/gdb/i387-tdep.c:1408: internal-error: invalid i387 regnum 152
The relevant last frames where this error happens are:
#8 0x0000563123d262fc in internal_error (file=0x563123e93fd8 "/home/smarchi/src/binutils-gdb/gdb/i387-tdep.c", line=1408, fmt=0x563123e94482 "invalid i387 regnum %d") at /home/smarchi/src/binutils-gdb/gdbsupport/errors.cc:55
#9 0x0000563123047d0d in i387_collect_xsave (regcache=0x5631269453f0, regnum=152, xsave=0x7ffd38402a20, gcore=0) at /home/smarchi/src/binutils-gdb/gdb/i387-tdep.c:1408
#10 0x0000563122c69e8a in amd64_collect_xsave (regcache=0x5631269453f0, regnum=152, xsave=0x7ffd38402a20, gcore=0) at /home/smarchi/src/binutils-gdb/gdb/amd64-tdep.c:3448
#11 0x0000563122c5e94c in amd64_linux_nat_target::store_registers (this=0x56312515fd10 <the_amd64_linux_nat_target>, regcache=0x5631269453f0, regnum=152) at /home/smarchi/src/binutils-gdb/gdb/amd64-linux-nat.c:335
#12 0x00005631234c8c80 in target_store_registers (regcache=0x5631269453f0, regno=152) at /home/smarchi/src/binutils-gdb/gdb/target.c:3485
#13 0x00005631232e8df7 in regcache::raw_write (this=0x5631269453f0, regnum=152, buf=0x56312759e468 "@\225\372\367\377\177") at /home/smarchi/src/binutils-gdb/gdb/regcache.c:765
#14 0x00005631232e8f0c in regcache::cooked_write (this=0x5631269453f0, regnum=152, buf=0x56312759e468 "@\225\372\367\377\177") at /home/smarchi/src/binutils-gdb/gdb/regcache.c:778
#15 0x00005631232e75ec in regcache::restore (this=0x5631269453f0, src=0x5631275eb130) at /home/smarchi/src/binutils-gdb/gdb/regcache.c:283
#16 0x0000563123083fc4 in infcall_suspend_state::restore (this=0x5631273ed930, gdbarch=0x56312718cf20, tp=0x5631270bca90, regcache=0x5631269453f0) at /home/smarchi/src/binutils-gdb/gdb/infrun.c:9103
#17 0x0000563123081eed in restore_infcall_suspend_state (inf_state=0x5631273ed930) at /home/smarchi/src/binutils-gdb/gdb/infrun.c:9151
The problem seems to be that amd64_linux_nat_target::store_registers
calls amd64_native_gregset_supplies_p to know whether gregset provides
fs_base. When !HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE,
amd64_native_gregset_supplies_p returns false. store_registers
therefore assumes that it must be an "xstate" register. This is of
course wrong, and that leads to the failed assertion when
i387_collect_xsave doesn't recognize the register.
amd64_linux_nat_target::store_registers could probably be fixed to
handle this case, but I don't think it's worth it, given that it would
only be to support very old kernels.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df5d438e33d7fc914ba9b6e0d6b019a8966c5fcc
[2] https://sourceware.org/git/?p=glibc.git;a=commit;h=c9cf6ddeebb7bb
[3] https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=88e4bc32686ebd0b1111a94f93eba2d334241f68
gdb/ChangeLog:
* configure.ac: Remove check for fs_base/gs_base in
user_regs_struct.
* configure: Re-generate.
* config.in: Re-generate.
* amd64-nat.c (amd64_native_gregset_reg_offset): Adjust.
* amd64-linux-nat.c (amd64_linux_nat_target::fetch_registers,
amd64_linux_nat_target::store_registers, ps_get_thread_area, ): Adjust.
gdbserver/ChangeLog:
* configure.ac: Remove check for fs_base/gs_base in
user_regs_struct.
* configure: Re-generate.
* config.in: Re-generate.
* linux-x86-low.cc (x86_64_regmap, x86_fill_gregset,
x86_store_gregset): Adjust.
If the search area is bigger than SEARCH_CHUNK_SIZE (16000), then you get
an error in gdbserver:
gdb: (gdb) find /w 0x3c43f0,+20000,0x04030201
gdb: Pattern not found.
gdbserver: Unable to access 3997 bytes of target memory at 0x3c8273, halting search.
The return value of any additional gdb_read_memory calls were compared with the
wrong value, this fixes it.
gdbserver/ChangeLog:
2020-04-22 Hannes Domani <ssbssa@yahoo.de>
* server.cc (handle_search_memory_1): Fix gdb_read_memory return value
comparison.
Simon pointed out that the windows-nat sharing series broke the Cygwin
build. This patch fixes the problem, by moving the Cygwin-specific
code to a new handler function. This approach is taken because this
code calls find_pc_partial_function, which isn't available in
gdbserver.
gdb/ChangeLog
2020-04-16 Tom Tromey <tromey@adacore.com>
* windows-nat.c (windows_nat::handle_access_violation): New
function.
* nat/windows-nat.h (handle_access_violation): Declare.
* nat/windows-nat.c (handle_exception): Move Cygwin code to
windows-nat.c. Call handle_access_violation.
gdbserver/ChangeLog
2020-04-16 Tom Tromey <tromey@adacore.com>
* win32-low.cc (windows_nat::handle_access_violation): New
function.
When compiling on Cygwin, we get:
CXX win32-low.o
/home/smarchi/src/binutils-gdb/gdbserver/win32-low.cc: In function ‘int get_child_debug_event(DWORD*, target_waitstatus*)’:
/home/smarchi/src/binutils-gdb/gdbserver/win32-low.cc:1459:17: error: format ‘%x’ expects argument of type ‘unsigned int’, but argument 2 has type ‘long int’ [-Werror=format=]
1459 | OUTMSG2 (("get_windows_debug_event - "
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
1460 | "unexpected stop in 0x%x (expecting 0x%x)\n",
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1461 | ptid.lwp (), desired_stop_thread_id));
| ~~~~~~~~~~~
| |
| long int
/home/smarchi/src/binutils-gdb/gdbserver/win32-low.cc:52:11: note: in definition of macro ‘OUTMSG2’
52 | printf X; \
| ^
/home/smarchi/src/binutils-gdb/gdbserver/win32-low.cc:1460:26: note: format string is defined here
1460 | "unexpected stop in 0x%x (expecting 0x%x)\n",
| ~^
| |
| unsigned int
| %lx
`ptid.lwp ()` is a `long` value, so it indeed needs the `l` size modifier.
gdbserver/ChangeLog:
* win32-low.cc (get_child_debug_event): Fix format string warning.
event-loop.c requires the client to provide some functions. This
patch implements these functions for gdbserver.
gdbserver/ChangeLog
2020-04-13 Tom Tromey <tom@tromey.com>
* server.c (invoke_async_signal_handlers)
(check_async_event_handlers, flush_streams, gdb_select): New
functions.
gdb_select.h and the event loop require some configure checks, so this
moves the needed checks to common.m4 and updates the configure
scripts.
gdb/ChangeLog
2020-04-13 Tom Tromey <tom@tromey.com>
* configure: Rebuild.
* configure.ac: Remove checks that are now in GDB_AC_COMMON.
gdbserver/ChangeLog
2020-04-13 Tom Tromey <tom@tromey.com>
* configure: Rebuild.
* config.in: Rebuild.
gdbsupport/ChangeLog
2020-04-13 Tom Tromey <tom@tromey.com>
* config.in, configure: Rebuild.
* common.m4 (GDB_AC_COMMON): Check for poll.h, sys/poll.h,
sys/select.h, and poll.
This changes gdbserver to also handle pending stops, the same way that
gdb does. This is PR gdb/22992.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
PR gdb/22992
* win32-low.c (child_continue): Call matching_pending_stop.
(get_child_debug_event): Call fetch_pending_stop. Push pending
stop when needed.
This changes the Windows gdbserver port to implement the
stopped_by_sw_breakpoint target method. This is needed to support
pending stops.
This is a separate patch now, because Pedro suggested splitting it out
for simpler bisecting, in the case that it introduces a bug.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.h (win32_process_target::stopped_by_sw_breakpoint)
(win32_process_target::supports_stopped_by_sw_breakpoint):
Declare.
* win32-low.c (win32_supports_z_point_type): Always handle
Z_PACKET_SW_BP.
(win32_insert_point): Call insert_memory_breakpoint when needed.
(win32_remove_point): Call remove_memory_breakpoint when needed.
(win32_process_target::stopped_by_sw_breakpoint)
(win32_process_target::supports_stopped_by_sw_breakpoint): New
methods.
(win32_target_ops): Update.
(maybe_adjust_pc): New function.
(win32_wait): Call maybe_adjust_pc.
This adds a decr_pc_after_break member to win32_target_ops and updates
the two Windows targets to set it.
Note that I can't test the win32-arm-low.c change.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.h (struct win32_target_ops) <decr_pc_after_break>: New
field.
* win32-i386-low.c (the_low_target): Update.
* win32-arm-low.c (the_low_target): Update.
This changes win32-low.c to implement the read_pc and write_pc
methods. A subsequent patch will need these.
Note that I have no way to test, or even compile, the win32-arm-low.c
change.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.h (win32_process_target::read_pc)
(win32_process_target::write_pc): Declare.
* win32-low.c (win32_process_target::read_pc)
(win32_process_target::write_pc): New methods.
* win32-i386-low.c (i386_win32_get_pc, i386_win32_set_pc): New
functions.
(the_low_target): Update.
* win32-arm-low.c (arm_win32_get_pc, arm_win32_set_pc): New
functions.
(the_low_target): Update.
This moves the wait_for_debug_event helper function to
nat/windows-nat.c, and changes gdbserver to use it.
wait_for_debug_event is a wrapper for WaitForDebugEvent that also sets
last_wait_event when appropriate. This is needed to properly handle
queued stops.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (wait_for_debug_event): Move to
nat/windows-nat.c.
* nat/windows-nat.h (wait_for_debug_event): Declare.
* nat/windows-nat.c (wait_for_debug_event): Move from
windows-nat.c. No longer static.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (win32_kill, get_child_debug_event): Use
wait_for_debug_event.
This adds a couple of functions to nat/windows-nat.c and changes gdb
and gdbserver to use them. One function checks the list of pending
stops for a match (not yet used by gdbserver, but will be in a
subsequent patch); and the other is a wrapper for ContinueDebugEvent
that always uses the last "real" stop event.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (windows_continue): Use matching_pending_stop and
continue_last_debug_event.
* nat/windows-nat.h (matching_pending_stop)
(continue_last_debug_event): Declare.
* nat/windows-nat.c (DEBUG_EVENTS): New define.
(matching_pending_stop, continue_last_debug_event): New
functions.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (child_continue): Call continue_last_debug_event.
Both gdb and gdbserver have a "handle_exception" function, the bulk of
which is shared between the two implementations. This patch arranges
for the entire thing to be moved into nat/windows-nat.c, with the
differences handled by callbacks. This patch introduces one more
callback to make this possible.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (MS_VC_EXCEPTION): Move to nat/windows-nat.c.
(handle_exception_result): Move to nat/windows-nat.h.
(DEBUG_EXCEPTION_SIMPLE): Remove.
(windows_nat::handle_ms_vc_exception): New function.
(handle_exception): Move to nat/windows-nat.c.
(get_windows_debug_event): Update.
(STATUS_WX86_BREAKPOINT, STATUS_WX86_SINGLE_STEP): Move to
nat/windows-nat.c.
* nat/windows-nat.h (handle_ms_vc_exception): Declare.
(handle_exception_result): Move from windows-nat.c.
(handle_exception): Declare.
* nat/windows-nat.c (MS_VC_EXCEPTION, handle_exception)
(STATUS_WX86_SINGLE_STEP, STATUS_WX86_BREAKPOINT): Move from
windows-nat.c.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (handle_exception): Remove.
(windows_nat::handle_ms_vc_exception): New function.
(get_child_debug_event): Add "continue_status" parameter.
Update.
(win32_wait): Update.
This changes nat/windows-nat.h to declare handle_load_dll and
handle_unload_dll. The embedding application is required to implement
these -- while the actual code was difficult to share due to some
other differences between the two programs, sharing the declaration
lets a subsequent patch share more code that uses these as callbacks.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (windows_nat::handle_load_dll)
(windows_nat::handle_unload_dll): Rename. No longer static.
* nat/windows-nat.h (handle_load_dll, handle_unload_dll):
Declare.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (windows_nat::handle_load_dll): Rename from
handle_load_dll. No longer static.
(windows_nat::handle_unload_dll): Rename from handle_unload_dll.
No longer static.
This changes gdbserver's implementation of handle_output_debug_string
to have the same calling convention as that of gdb. This allows for
sharing some more code in a subsequent patch.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (windows_nat::handle_output_debug_string):
Rename. No longer static.
* nat/windows-nat.h (handle_output_debug_string): Declare.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (handle_output_debug_string): Add parameter. Change
return type.
(win32_kill, get_child_debug_event): Update.
This moves get_image_name to nat/windows-nat.c so that it can be
shared between gdb and gdbserver.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (get_image_name): Move to nat/windows-nat.c.
(handle_load_dll): Update.
* nat/windows-nat.c (get_image_name): Move from windows-nat.c.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (get_image_name): Remove.
(handle_load_dll): Update.
This changes gdb and gdbserver to use the same calling convention for
the "thread_rec" helper function. Fully merging these is difficult
due to differences in how threads are managed by the enclosing
applications; but sharing a declaration makes it possible for future
shared code to call this method.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (enum thread_disposition_type): Move to
nat/windows-nat.h.
(windows_nat::thread_rec): Rename from thread_rec. No longer
static.
(windows_add_thread, windows_nat_target::fetch_registers)
(windows_nat_target::store_registers, handle_exception)
(windows_nat_target::resume, get_windows_debug_event)
(windows_nat_target::get_tib_address)
(windows_nat_target::thread_name)
(windows_nat_target::thread_alive): Update.
* nat/windows-nat.h (enum thread_disposition_type): Move from
windows-nat.c.
(thread_rec): Declare.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (windows_nat::thread_rec): Rename from thread_rec.
No longer static. Change parameters.
(child_add_thread, child_fetch_inferior_registers)
(child_store_inferior_registers, win32_resume)
(win32_get_tib_address): Update.
This adds "suspend" and "resume" methods to windows_thread_info, and
changes gdb and gdbserver to share this code.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (thread_rec): Use windows_thread_info::suspend.
(windows_continue): Use windows_continue::resume.
* nat/windows-nat.h (struct windows_thread_info) <suspend,
resume>: Declare new methods.
* nat/windows-nat.c: New file.
* configure.nat (NATDEPFILES): Add nat/windows-nat.o when needed.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (win32_require_context, suspend_one_thread): Use
windows_thread_info::suspend.
(continue_one_thread): Use windows_thread_info::resume.
* configure.srv (srv_tgtobj): Add windows-nat.o when needed.
This changes a couple of fields of windows_thread_info to have type
"bool". It also updates the comment of another field, to clarify the
possible values it can hold.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (thread_rec)
(windows_nat_target::fetch_registers): Update.
* nat/windows-nat.h (struct windows_thread_info) <suspended>:
Update comment.
<debug_registers_changed, reload_context>: Now bool.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-i386-low.c (update_debug_registers)
(i386_prepare_to_resume, i386_thread_added): Update.
This adds a constructor, destructor, and member initializers to
windows_thread_info, and changes gdb and gdbserver to use new and
delete.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (windows_add_thread): Use new.
(windows_init_thread_list, windows_delete_thread): Use delete.
(get_windows_debug_event): Update.
* nat/windows-nat.h (struct windows_thread_info): Add constructor,
destructor, and initializers.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.c (child_add_thread): Use new.
(delete_thread_info): Use delete.
This introduces a new file, nat/windows-nat.h, which holds the
definition of windows_thread_info. This is now shared between gdb and
gdbserver.
Note that the two implementations different slightly. gdb had a
couple of fields ("name" and "reload_context") that gdbserver did not;
while gdbserver had one field ("base_context") that gdb did not, plus
better comments. The new file preserves all the fields, and the
comments.
gdb/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* windows-nat.c (struct windows_thread_info): Remove.
* nat/windows-nat.h: New file.
gdbserver/ChangeLog
2020-04-08 Tom Tromey <tromey@adacore.com>
* win32-low.h (struct windows_thread_info): Remove.
gdbserver/ChangeLog:
2020-04-02 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Remove the 'get_ipa_tdesc_idx' linux target op and let a concrete
linux target define the op by overriding the declaration in
process_stratum_target.
* linux-low.h (struct linux_target_ops): Remove the op.
(class linux_process_target) <get_ipa_tdesc_idx>: Remove.
* linux-low.cc (linux_process_target::get_ipa_tdesc_idx): Remove.
* linux-x86-low.cc (class x86_target) <get_ipa_tdesc_idx>: Declare.
(x86_get_ipa_tdesc_idx): Turn into...
(x86_target::get_ipa_tdesc_idx): ...this.
(the_low_target): Remove the op field.
* linux-ppc-low.cc (class ppc_target) <get_ipa_tdesc_idx>: Declare.
(ppc_get_ipa_tdesc_idx): Turn into...
(ppc_target::get_ipa_tdesc_idx): ...this.
(the_low_target): Remove the op field.
* linux-s390-low.cc (class s390_target) <get_ipa_tdesc_idx>: Declare.
(s390_get_ipa_tdesc_idx): Turn into...
(s390_target::get_ipa_tdesc_idx): ...this.
(the_low_target): Remove the op field.
All the linux low targets except arm define the
'supports_hardware_single_step' op to return true. Hence, we override
the method to return true in linux_process_target, and remove the
definitions in all the linux low targets but arm.
gdbserver/ChangeLog:
2020-04-02 Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Remove the 'supports_hardware_single_step' linux target op and
override the process_stratum_target's op definition in
linux_process_target to return true.
* linux-low.h (struct linux_target_ops): Remove the op.
(class linux_process_target) <finish_step_over>
<maybe_hw_step>: Declare.
* linux-low.cc (can_hardware_single_step): Remove.
(maybe_hw_step): Turn into...
(linux_process_target::maybe_hw_step): ...this.
(finish_step_over): Turn into...
(linux_process_target::finish_step_over): ...this.
(linux_process_target::supports_hardware_single_step): Update
to return true.
Update the callers below.
(linux_process_target::single_step)
(linux_process_target::resume_one_lwp_throw)
* linux-arm-low.cc (class arm_target)
<supports_hardware_single_step>: Declare.
(arm_supports_hardware_single_step): Turn into...
(arm_target::supports_hardware_single_step): ...this.
(the_low_target): Remove the op field.
* linux-x86-low.cc (x86_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-aarch64-low.cc (aarch64_supports_hardware_single_step):
Remove.
(the_low_target): Remove the op field.
* linux-bfin-low.cc (bfin_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-crisv32-low.cc (cris_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-m32r-low.cc (m32r_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-m68k-low.cc (m68k_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-ppc-low.cc (ppc_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-s390-low.cc (s390_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-sh-low.cc (sh_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-tic6x-low.cc (tic6x_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-tile-low.cc (tile_supports_hardware_single_step): Remove.
(the_low_target): Remove the op field.
* linux-xtensa-low.cc (xtensa_supports_hardware_single_step):
Remove.
(the_low_target): Remove the op field.
