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Re: [PATCH] solib-svr4: Pass down svr4_info as much as possible
On 4/19/19 4:03 PM, Simon Marchi wrote:
> On 2019-04-10 10:49 p.m., Simon Marchi wrote:
>> I am not able to reproduce the problem, and the test doesn't fail here, without
>> the rest of the patch applied. I think it's because on my system gdb doesn't use
>> the probe based interface.
>>
>> Anyhow, the fix makes sense. Since the probe is deleted on objfile destruction, the
>> corresponding probe_and_action structures should too.
>>
>> Simon
>
> While reviewing this patch, I had written the patch below to experiment, and
> while it's not super important, I think it's a good cleanup.
>
>
> From aedf5f7d846672ba6edc2780853baa43f35dd3c4 Mon Sep 17 00:00:00 2001
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Date: Wed, 10 Apr 2019 22:02:33 -0400
> Subject: [PATCH] solib-svr4: Pass down svr4_info as much as possible
>
> While reviewing
>
> https://sourceware.org/ml/gdb-patches/2019-04/msg00141.html
>
> I noticed that we relied heavily on global state through the
> get_svr4_info function, which uses current_program_space. I thought we
> could improve this (make things more explicit and easier to follow) by
>
> - Making get_svr4_info accept a program_space parameter, making it
> return the SVR4 info for that program space.
> - Passing down the svr4_info object from callers as much as possible.
>
> This means looking up the svr4_info for the appropriate program space at
> the entry points of the solib-svr4.c file and passing it down. For now,
> these entry points (most of them are "methods" of svr4_so_ops) rely on
> current_program_space, but we can later try to change the target_so_ops
> interface to pass down the program space.
Seems fine to me. Please go ahead.
Thinking a bit longer term we could end up passing down an inferior pointer
around in functions in this file instead. That's because we use target_gdbarch()
in these routines, which is really inferior->gdbarch. The program space can be
found at inferior->pspace. Etc. Then again, the end up going target calls in
a number of these routines, which implicitly refers to the current
inferior/thread/pspace too... Anyway, I'm happy with the patch as is, TBC.
>
> gdb/ChangeLog:
>
> * solib-svr4.c (get_svr4_info): Add pspace parameter.
> (svr4_keep_data_in_core): Pass current_program_space to get_svr4_info.
> (open_symbol_file_object): Likewise.
> (svr4_default_sos): Add info parameter.
> (svr4_read_so_list): Likewise.
> (svr4_current_sos_direct): Adjust functions calls to pass down
> info.
> (svr4_current_sos_1): Add info parameter.
> (svr4_current_sos): Call get_svr4_info, pass info down to
> svr4_current_sos_1.
> (svr4_fetch_objfile_link_map): Pass objfile->pspace to
> get_svr4_info.
> (svr4_in_dynsym_resolve_code): Pass current_program_space to
> get_svr4_info.
> (probes_table_htab_remove_objfile_probes): Pass objfile->pspace
> to get_svr4_info.
> (probes_table_remove_objfile_probes): Likewise.
> (register_solib_event_probe): Add info parameter.
> (solist_update_incremental): Pass info parameter down to
> svr4_read_so_list.
> (disable_probes_interface): Add info parameter.
> (svr4_handle_solib_event): Pass current_program_space to
> get_svr4_info. Adjust disable_probes_interface cleanup.
> (svr4_create_probe_breakpoints): Add info parameter, pass it
> down to register_solib_event_probe.
> (svr4_create_solib_event_breakpoints): Add info parameter,
> pass it down to svr4_create_probe_breakpoints.
> (enable_break): Pass info down to
> svr4_create_solib_event_breakpoints.
> (svr4_solib_create_inferior_hook): Pass current_program_space to
> get_svr4_info.
> (svr4_clear_solib): Likewise.
> ---
> gdb/solib-svr4.c | 84 +++++++++++++++++++++++-------------------------
> 1 file changed, 41 insertions(+), 43 deletions(-)
>
> diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
> index 2c79dfec2bb6..2aa7b95ce6c1 100644
> --- a/gdb/solib-svr4.c
> +++ b/gdb/solib-svr4.c
> @@ -391,21 +391,21 @@ svr4_pspace_data_cleanup (struct program_space *pspace, void *arg)
> xfree (info);
> }
>
> -/* Get the current svr4 data. If none is found yet, add it now. This
> - function always returns a valid object. */
> +/* Get the svr4 data for program space PSPACE. If none is found yet, add it now.
> + This function always returns a valid object. */
>
> static struct svr4_info *
> -get_svr4_info (void)
> +get_svr4_info (program_space *pspace)
> {
> struct svr4_info *info;
>
> - info = (struct svr4_info *) program_space_data (current_program_space,
> + info = (struct svr4_info *) program_space_data (pspace,
> solib_svr4_pspace_data);
> if (info != NULL)
> return info;
>
> info = XCNEW (struct svr4_info);
> - set_program_space_data (current_program_space, solib_svr4_pspace_data, info);
> + set_program_space_data (pspace, solib_svr4_pspace_data, info);
> return info;
> }
>
> @@ -940,7 +940,7 @@ svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
> CORE_ADDR ldsomap;
> CORE_ADDR name_lm;
>
> - info = get_svr4_info ();
> + info = get_svr4_info (current_program_space);
>
> info->debug_base = 0;
> locate_base (info);
> @@ -969,7 +969,7 @@ open_symbol_file_object (int from_tty)
> struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
> int l_name_size = TYPE_LENGTH (ptr_type);
> gdb::byte_vector l_name_buf (l_name_size);
> - struct svr4_info *info = get_svr4_info ();
> + struct svr4_info *info = get_svr4_info (current_program_space);
> symfile_add_flags add_flags = 0;
>
> if (from_tty)
> @@ -1264,9 +1264,8 @@ svr4_current_sos_via_xfer_libraries (struct svr4_library_list *list,
> linker, build a fallback list from other sources. */
>
> static struct so_list *
> -svr4_default_sos (void)
> +svr4_default_sos (svr4_info *info)
> {
> - struct svr4_info *info = get_svr4_info ();
> struct so_list *newobj;
>
> if (!info->debug_loader_offset_p)
> @@ -1296,7 +1295,7 @@ svr4_default_sos (void)
> represent only part of the inferior library list. */
>
> static int
> -svr4_read_so_list (CORE_ADDR lm, CORE_ADDR prev_lm,
> +svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
> struct so_list ***link_ptr_ptr, int ignore_first)
> {
> CORE_ADDR first_l_name = 0;
> @@ -1331,8 +1330,6 @@ svr4_read_so_list (CORE_ADDR lm, CORE_ADDR prev_lm,
> decide when to ignore it. */
> if (ignore_first && li->l_prev == 0)
> {
> - struct svr4_info *info = get_svr4_info ();
> -
> first_l_name = li->l_name;
> info->main_lm_addr = li->lm_addr;
> continue;
> @@ -1400,7 +1397,7 @@ svr4_current_sos_direct (struct svr4_info *info)
> if (library_list.main_lm)
> info->main_lm_addr = library_list.main_lm;
>
> - return library_list.head ? library_list.head : svr4_default_sos ();
> + return library_list.head ? library_list.head : svr4_default_sos (info);
> }
>
> /* Always locate the debug struct, in case it has moved. */
> @@ -1410,7 +1407,7 @@ svr4_current_sos_direct (struct svr4_info *info)
> /* If we can't find the dynamic linker's base structure, this
> must not be a dynamically linked executable. Hmm. */
> if (! info->debug_base)
> - return svr4_default_sos ();
> + return svr4_default_sos (info);
>
> /* Assume that everything is a library if the dynamic loader was loaded
> late by a static executable. */
> @@ -1428,7 +1425,7 @@ svr4_current_sos_direct (struct svr4_info *info)
> `struct so_list' nodes. */
> lm = solib_svr4_r_map (info);
> if (lm)
> - svr4_read_so_list (lm, 0, &link_ptr, ignore_first);
> + svr4_read_so_list (info, lm, 0, &link_ptr, ignore_first);
>
> /* On Solaris, the dynamic linker is not in the normal list of
> shared objects, so make sure we pick it up too. Having
> @@ -1436,12 +1433,12 @@ svr4_current_sos_direct (struct svr4_info *info)
> for skipping dynamic linker resolver code. */
> lm = solib_svr4_r_ldsomap (info);
> if (lm)
> - svr4_read_so_list (lm, 0, &link_ptr, 0);
> + svr4_read_so_list (info, lm, 0, &link_ptr, 0);
>
> cleanup.release ();
>
> if (head == NULL)
> - return svr4_default_sos ();
> + return svr4_default_sos (info);
>
> return head;
> }
> @@ -1450,10 +1447,8 @@ svr4_current_sos_direct (struct svr4_info *info)
> method. */
>
> static struct so_list *
> -svr4_current_sos_1 (void)
> +svr4_current_sos_1 (svr4_info *info)
> {
> - struct svr4_info *info = get_svr4_info ();
> -
> /* If the solib list has been read and stored by the probes
> interface then we return a copy of the stored list. */
> if (info->solib_list != NULL)
> @@ -1468,7 +1463,8 @@ svr4_current_sos_1 (void)
> static struct so_list *
> svr4_current_sos (void)
> {
> - struct so_list *so_head = svr4_current_sos_1 ();
> + svr4_info *info = get_svr4_info (current_program_space);
> + struct so_list *so_head = svr4_current_sos_1 (info);
> struct mem_range vsyscall_range;
>
> /* Filter out the vDSO module, if present. Its symbol file would
> @@ -1548,7 +1544,7 @@ CORE_ADDR
> svr4_fetch_objfile_link_map (struct objfile *objfile)
> {
> struct so_list *so;
> - struct svr4_info *info = get_svr4_info ();
> + struct svr4_info *info = get_svr4_info (objfile->pspace);
>
> /* Cause svr4_current_sos() to be run if it hasn't been already. */
> if (info->main_lm_addr == 0)
> @@ -1601,7 +1597,7 @@ match_main (const char *soname)
> int
> svr4_in_dynsym_resolve_code (CORE_ADDR pc)
> {
> - struct svr4_info *info = get_svr4_info ();
> + struct svr4_info *info = get_svr4_info (current_program_space);
>
> return ((pc >= info->interp_text_sect_low
> && pc < info->interp_text_sect_high)
> @@ -1681,7 +1677,7 @@ probes_table_htab_remove_objfile_probes (void **slot, void *info)
> struct objfile *objfile = (struct objfile *) info;
>
> if (pa->objfile == objfile)
> - htab_clear_slot (get_svr4_info ()->probes_table, slot);
> + htab_clear_slot (get_svr4_info (objfile->pspace)->probes_table, slot);
>
> return 1;
> }
> @@ -1691,7 +1687,7 @@ probes_table_htab_remove_objfile_probes (void **slot, void *info)
> static void
> probes_table_remove_objfile_probes (struct objfile *objfile)
> {
> - svr4_info *info = get_svr4_info ();
> + svr4_info *info = get_svr4_info (objfile->pspace);
> if (info->probes_table != nullptr)
> htab_traverse_noresize (info->probes_table,
> probes_table_htab_remove_objfile_probes, objfile);
> @@ -1701,11 +1697,10 @@ probes_table_remove_objfile_probes (struct objfile *objfile)
> probes table. */
>
> static void
> -register_solib_event_probe (struct objfile *objfile,
> +register_solib_event_probe (svr4_info *info, struct objfile *objfile,
> probe *prob, CORE_ADDR address,
> enum probe_action action)
> {
> - struct svr4_info *info = get_svr4_info ();
> struct probe_and_action lookup, *pa;
> void **slot;
>
> @@ -1857,7 +1852,7 @@ solist_update_incremental (struct svr4_info *info, CORE_ADDR lm)
> above check and deferral to solist_update_full ensures
> that this call to svr4_read_so_list will never see the
> first element. */
> - if (!svr4_read_so_list (lm, prev_lm, &link, 0))
> + if (!svr4_read_so_list (info, lm, prev_lm, &link, 0))
> return 0;
> }
>
> @@ -1869,10 +1864,8 @@ solist_update_incremental (struct svr4_info *info, CORE_ADDR lm)
> ones set up for the probes-based interface are adequate. */
>
> static void
> -disable_probes_interface ()
> +disable_probes_interface (svr4_info *info)
> {
> - struct svr4_info *info = get_svr4_info ();
> -
> warning (_("Probes-based dynamic linker interface failed.\n"
> "Reverting to original interface.\n"));
>
> @@ -1887,7 +1880,7 @@ disable_probes_interface ()
> static void
> svr4_handle_solib_event (void)
> {
> - struct svr4_info *info = get_svr4_info ();
> + struct svr4_info *info = get_svr4_info (current_program_space);
> struct probe_and_action *pa;
> enum probe_action action;
> struct value *val = NULL;
> @@ -1900,7 +1893,10 @@ svr4_handle_solib_event (void)
>
> /* If anything goes wrong we revert to the original linker
> interface. */
> - auto cleanup = make_scope_exit (disable_probes_interface);
> + auto cleanup = make_scope_exit ([info] ()
> + {
> + disable_probes_interface (info);
> + });
>
> pc = regcache_read_pc (get_current_regcache ());
> pa = solib_event_probe_at (info, pc);
> @@ -2055,7 +2051,7 @@ svr4_update_solib_event_breakpoints (void)
> probe. */
>
> static void
> -svr4_create_probe_breakpoints (struct gdbarch *gdbarch,
> +svr4_create_probe_breakpoints (svr4_info *info, struct gdbarch *gdbarch,
> const std::vector<probe *> *probes,
> struct objfile *objfile)
> {
> @@ -2068,7 +2064,7 @@ svr4_create_probe_breakpoints (struct gdbarch *gdbarch,
> CORE_ADDR address = p->get_relocated_address (objfile);
>
> create_solib_event_breakpoint (gdbarch, address);
> - register_solib_event_probe (objfile, p, address, action);
> + register_solib_event_probe (info, objfile, p, address, action);
> }
> }
>
> @@ -2088,7 +2084,7 @@ svr4_create_probe_breakpoints (struct gdbarch *gdbarch,
> marker function. */
>
> static void
> -svr4_create_solib_event_breakpoints (struct gdbarch *gdbarch,
> +svr4_create_solib_event_breakpoints (svr4_info *info, struct gdbarch *gdbarch,
> CORE_ADDR address)
> {
> struct obj_section *os;
> @@ -2151,7 +2147,7 @@ svr4_create_solib_event_breakpoints (struct gdbarch *gdbarch,
> }
>
> if (all_probes_found)
> - svr4_create_probe_breakpoints (gdbarch, probes, os->objfile);
> + svr4_create_probe_breakpoints (info, gdbarch, probes, os->objfile);
>
> if (all_probes_found)
> return;
> @@ -2282,7 +2278,7 @@ enable_break (struct svr4_info *info, int from_tty)
> + bfd_section_size (tmp_bfd, interp_sect);
> }
>
> - svr4_create_solib_event_breakpoints (target_gdbarch (), sym_addr);
> + svr4_create_solib_event_breakpoints (info, target_gdbarch (), sym_addr);
> return 1;
> }
> }
> @@ -2444,7 +2440,7 @@ enable_break (struct svr4_info *info, int from_tty)
>
> if (sym_addr != 0)
> {
> - svr4_create_solib_event_breakpoints (target_gdbarch (),
> + svr4_create_solib_event_breakpoints (info, target_gdbarch (),
> load_addr + sym_addr);
> return 1;
> }
> @@ -2470,7 +2466,8 @@ enable_break (struct svr4_info *info, int from_tty)
> sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch (),
> sym_addr,
> current_top_target ());
> - svr4_create_solib_event_breakpoints (target_gdbarch (), sym_addr);
> + svr4_create_solib_event_breakpoints (info, target_gdbarch (),
> + sym_addr);
> return 1;
> }
> }
> @@ -2487,7 +2484,8 @@ enable_break (struct svr4_info *info, int from_tty)
> sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch (),
> sym_addr,
> current_top_target ());
> - svr4_create_solib_event_breakpoints (target_gdbarch (), sym_addr);
> + svr4_create_solib_event_breakpoints (info, target_gdbarch (),
> + sym_addr);
> return 1;
> }
> }
> @@ -3010,7 +3008,7 @@ svr4_solib_create_inferior_hook (int from_tty)
> {
> struct svr4_info *info;
>
> - info = get_svr4_info ();
> + info = get_svr4_info (current_program_space);
>
> /* Clear the probes-based interface's state. */
> free_probes_table (info);
> @@ -3036,7 +3034,7 @@ svr4_clear_solib (void)
> {
> struct svr4_info *info;
>
> - info = get_svr4_info ();
> + info = get_svr4_info (current_program_space);
> info->debug_base = 0;
> info->debug_loader_offset_p = 0;
> info->debug_loader_offset = 0;
>
Thanks,
Pedro Alves