Re: [PATCH v3 1/1] gdb: avoid conversion of SIGSEGV to SIGTRAP on user breakpoints

[Andrew Burgess <aburgess@redhat.com>]

Klaus Gerlicher <klaus.gerlicher@intel.com> writes:

> From: "Gerlicher, Klaus" <klaus.gerlicher@intel.com>
>
> GDB converts signals GDB_SIGNAL_ILL, GDB_SIGNAL_SEGV and GDB_SIGNAL_EMT to
> GDB_SIGNAL_SEGV if a breakpoint is inserted at the fault location.  If, due
> to imprecise page fault reporting, a breakpoint is at the same address as
> the fault address, this signal would always be reported as GDB_SIGNAL_TRAP.
>
> Add a new gdbarch function that allows the signal conversion from SIGNAL_SEGV
> to SIGNAL_TRAP to be skipped for an architecture.

LGTM.

Approved-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew


> ---
>  gdb/gdbarch-gen.c         | 22 ++++++++++++++++++++++
>  gdb/gdbarch-gen.h         |  7 +++++++
>  gdb/gdbarch_components.py | 12 ++++++++++++
>  gdb/infrun.c              |  4 +++-
>  4 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/gdbarch-gen.c b/gdb/gdbarch-gen.c
> index d05c7a3cbdf..255f851ffa3 100644
> --- a/gdb/gdbarch-gen.c
> +++ b/gdb/gdbarch-gen.c
> @@ -260,6 +260,7 @@ struct gdbarch
>    gdbarch_get_pc_address_flags_ftype *get_pc_address_flags = default_get_pc_address_flags;
>    gdbarch_read_core_file_mappings_ftype *read_core_file_mappings = default_read_core_file_mappings;
>    gdbarch_use_target_description_from_corefile_notes_ftype *use_target_description_from_corefile_notes = default_use_target_description_from_corefile_notes;
> +  gdbarch_imprecise_pagefault_reporting_ftype *imprecise_pagefault_reporting = [] () -> bool {return false;};
>  };
>  
>  /* Create a new ``struct gdbarch'' based on information provided by
> @@ -531,6 +532,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
>    /* Skip verify of get_pc_address_flags, invalid_p == 0.  */
>    /* Skip verify of read_core_file_mappings, invalid_p == 0.  */
>    /* Skip verify of use_target_description_from_corefile_notes, invalid_p == 0.  */
> +  /* Skip verify of imprecise_pagefault_reporting, invalid_p == 0.  */
>    if (!log.empty ())
>      internal_error (_("verify_gdbarch: the following are invalid ...%s"),
>  		    log.c_str ());
> @@ -1396,6 +1398,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
>    gdb_printf (file,
>  	      "gdbarch_dump: use_target_description_from_corefile_notes = <%s>\n",
>  	      host_address_to_string (gdbarch->use_target_description_from_corefile_notes));
> +  gdb_printf (file,
> +	      "gdbarch_dump: imprecise_pagefault_reporting = <%s>\n",
> +	      host_address_to_string (gdbarch->imprecise_pagefault_reporting));
>    if (gdbarch->dump_tdep != NULL)
>      gdbarch->dump_tdep (gdbarch, file);
>  }
> @@ -5507,3 +5512,20 @@ set_gdbarch_use_target_description_from_corefile_notes (struct gdbarch *gdbarch,
>  {
>    gdbarch->use_target_description_from_corefile_notes = use_target_description_from_corefile_notes;
>  }
> +
> +bool
> +gdbarch_imprecise_pagefault_reporting (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  gdb_assert (gdbarch->imprecise_pagefault_reporting != NULL);
> +  if (gdbarch_debug >= 2)
> +    gdb_printf (gdb_stdlog, "gdbarch_imprecise_pagefault_reporting called\n");
> +  return gdbarch->imprecise_pagefault_reporting ();
> +}
> +
> +void
> +set_gdbarch_imprecise_pagefault_reporting (struct gdbarch *gdbarch,
> +					   gdbarch_imprecise_pagefault_reporting_ftype imprecise_pagefault_reporting)
> +{
> +  gdbarch->imprecise_pagefault_reporting = imprecise_pagefault_reporting;
> +}
> diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
> index 9fda85f860f..e2ca6e59680 100644
> --- a/gdb/gdbarch-gen.h
> +++ b/gdb/gdbarch-gen.h
> @@ -1778,3 +1778,10 @@ extern void set_gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, gdbarc
>  typedef bool (gdbarch_use_target_description_from_corefile_notes_ftype) (struct gdbarch *gdbarch, struct bfd *corefile_bfd);
>  extern bool gdbarch_use_target_description_from_corefile_notes (struct gdbarch *gdbarch, struct bfd *corefile_bfd);
>  extern void set_gdbarch_use_target_description_from_corefile_notes (struct gdbarch *gdbarch, gdbarch_use_target_description_from_corefile_notes_ftype *use_target_description_from_corefile_notes);
> +
> +/* Returns true if architecture has imprecise pagefault reporting.  This is
> +   used in conversion of SIGSEGV to SIGTRAP for an architecture. */
> +
> +typedef bool (gdbarch_imprecise_pagefault_reporting_ftype) ();
> +extern bool gdbarch_imprecise_pagefault_reporting (struct gdbarch *gdbarch);
> +extern void set_gdbarch_imprecise_pagefault_reporting (struct gdbarch *gdbarch, gdbarch_imprecise_pagefault_reporting_ftype *imprecise_pagefault_reporting);
> diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
> index cc7c6d8677b..8f518e1052a 100644
> --- a/gdb/gdbarch_components.py
> +++ b/gdb/gdbarch_components.py
> @@ -2815,3 +2815,15 @@ The corefile's bfd is passed through COREFILE_BFD.
>      predefault="default_use_target_description_from_corefile_notes",
>      invalid=False,
>  )
> +
> +Function(
> +    comment="""
> +Returns true if architecture has imprecise pagefault reporting.  This is
> +used in conversion of SIGSEGV to SIGTRAP for an architecture.
> +""",
> +    type="bool",
> +    name="imprecise_pagefault_reporting",
> +    params=[],
> +    predefault="[] () -> bool {return false;}",
> +    invalid=False
> +)
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index 43eca814e29..eb34aed09e0 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -6138,7 +6138,9 @@ handle_inferior_event (struct execution_control_state *ecs)
>       stack.  */
>    if (ecs->ws.kind () == TARGET_WAITKIND_STOPPED
>        && (ecs->ws.sig () == GDB_SIGNAL_ILL
> -	  || ecs->ws.sig () == GDB_SIGNAL_SEGV
> +	  || (ecs->ws.sig () == GDB_SIGNAL_SEGV
> +	      && !gdbarch_imprecise_pagefault_reporting
> +	        (current_inferior ()->arch ()))
>  	  || ecs->ws.sig () == GDB_SIGNAL_EMT))
>      {
>        struct regcache *regcache = get_thread_regcache (ecs->event_thread);
> -- 
> 2.34.1
>
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