[PATCH] gdb: Support DW_LLE_start_end

[PATCH] gdb: Support DW_LLE_start_end

[Andreas Schwab]

Without that it is impossible to debug on riscv64.

gdb/
	PR symtab/27999
	* dwarf2/loc.c (decode_debug_loclists_addresses): Support
	DW_LLE_start_end.
---
 gdb/dwarf2/loc.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c
index b7e30e3cb4a..d57cdc165ba 100644
--- a/gdb/dwarf2/loc.c
+++ b/gdb/dwarf2/loc.c
@@ -255,9 +255,27 @@ decode_debug_loclists_addresses (dwarf2_per_cu_data *per_cu,
       *new_ptr = loc_ptr;
       return DEBUG_LOC_OFFSET_PAIR;
 
+    case DW_LLE_start_end:
+      if (loc_ptr + 2 * addr_size > buf_end)
+	return DEBUG_LOC_BUFFER_OVERFLOW;
+
+      if (signed_addr_p)
+	*low = extract_signed_integer (loc_ptr, addr_size, byte_order);
+      else
+	*low = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
+
+      loc_ptr += addr_size;
+      if (signed_addr_p)
+	*high = extract_signed_integer (loc_ptr, addr_size, byte_order);
+      else
+	*high = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
+
+      loc_ptr += addr_size;
+      *new_ptr = loc_ptr;
+      return DEBUG_LOC_START_END;
+
     /* Following cases are not supported yet.  */
     case DW_LLE_startx_endx:
-    case DW_LLE_start_end:
     case DW_LLE_default_location:
     default:
       return DEBUG_LOC_INVALID_ENTRY;
-- 
2.31.1


-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: [PATCH] gdb: Support DW_LLE_start_end

[Simon Marchi]

On 2021-06-21 5:50 a.m., Andreas Schwab wrote:
> Without that it is impossible to debug on riscv64.
> 
> gdb/
> 	PR symtab/27999
> 	* dwarf2/loc.c (decode_debug_loclists_addresses): Support
> 	DW_LLE_start_end.
> ---
>  gdb/dwarf2/loc.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c
> index b7e30e3cb4a..d57cdc165ba 100644
> --- a/gdb/dwarf2/loc.c
> +++ b/gdb/dwarf2/loc.c
> @@ -255,9 +255,27 @@ decode_debug_loclists_addresses (dwarf2_per_cu_data *per_cu,
>        *new_ptr = loc_ptr;
>        return DEBUG_LOC_OFFSET_PAIR;
>  
> +    case DW_LLE_start_end:
> +      if (loc_ptr + 2 * addr_size > buf_end)
> +	return DEBUG_LOC_BUFFER_OVERFLOW;
> +
> +      if (signed_addr_p)
> +	*low = extract_signed_integer (loc_ptr, addr_size, byte_order);
> +      else
> +	*low = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
> +
> +      loc_ptr += addr_size;
> +      if (signed_addr_p)
> +	*high = extract_signed_integer (loc_ptr, addr_size, byte_order);
> +      else
> +	*high = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
> +
> +      loc_ptr += addr_size;
> +      *new_ptr = loc_ptr;
> +      return DEBUG_LOC_START_END;
> +
>      /* Following cases are not supported yet.  */
>      case DW_LLE_startx_endx:
> -    case DW_LLE_start_end:
>      case DW_LLE_default_location:
>      default:
>        return DEBUG_LOC_INVALID_ENTRY;
> 

Could you please try adding a gdb.dwarf2 test case?  Support for
building loclists already exists, so there should be little new
infrastructure needed, just add support for DW_LLE_start_end (see where
DW_LLE_start_length is handled).

I'm thinking of a test case where we would test all the DW_LLE_*
operations we support.

Simon

Re: [PATCH] gdb: Support DW_LLE_start_end

[Andreas Schwab]

Without that it is impossible to debug on riscv64.

gdb/
	PR symtab/27999
	* dwarf2/loc.c (decode_debug_loclists_addresses): Support
	DW_LLE_start_end.

gdb/testsuite/
	PR symtab/27999
	* lib/dwarf.exp (start_end): New proc inside loclists.
	* gdb.dwarf2/loclists-start-end.exp: New file.
	* gdb.dwarf2/loclists-start-end.c: New file.
---
 gdb/dwarf2/loc.c                              |  20 ++-
 gdb/testsuite/gdb.dwarf2/loclists-start-end.c |  37 +++++
 .../gdb.dwarf2/loclists-start-end.exp         | 137 ++++++++++++++++++
 gdb/testsuite/lib/dwarf.exp                   |  29 ++++
 4 files changed, 222 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.dwarf2/loclists-start-end.c
 create mode 100644 gdb/testsuite/gdb.dwarf2/loclists-start-end.exp

diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c
index b7e30e3cb4a..d57cdc165ba 100644
--- a/gdb/dwarf2/loc.c
+++ b/gdb/dwarf2/loc.c
@@ -255,9 +255,27 @@ decode_debug_loclists_addresses (dwarf2_per_cu_data *per_cu,
       *new_ptr = loc_ptr;
       return DEBUG_LOC_OFFSET_PAIR;
 
+    case DW_LLE_start_end:
+      if (loc_ptr + 2 * addr_size > buf_end)
+	return DEBUG_LOC_BUFFER_OVERFLOW;
+
+      if (signed_addr_p)
+	*low = extract_signed_integer (loc_ptr, addr_size, byte_order);
+      else
+	*low = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
+
+      loc_ptr += addr_size;
+      if (signed_addr_p)
+	*high = extract_signed_integer (loc_ptr, addr_size, byte_order);
+      else
+	*high = extract_unsigned_integer (loc_ptr, addr_size, byte_order);
+
+      loc_ptr += addr_size;
+      *new_ptr = loc_ptr;
+      return DEBUG_LOC_START_END;
+
     /* Following cases are not supported yet.  */
     case DW_LLE_startx_endx:
-    case DW_LLE_start_end:
     case DW_LLE_default_location:
     default:
       return DEBUG_LOC_INVALID_ENTRY;
diff --git a/gdb/testsuite/gdb.dwarf2/loclists-start-end.c b/gdb/testsuite/gdb.dwarf2/loclists-start-end.c
new file mode 100644
index 00000000000..2bffbf2ac4c
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/loclists-start-end.c
@@ -0,0 +1,37 @@
+/* Copyright (C) 2021 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+static int
+func1 (void)
+{
+  asm ("func1_label: .global func1_label\n");
+  return 1;
+}
+
+static int
+func2 (void)
+{
+  asm ("func2_label: .global func2_label\n");
+  return 2;
+}
+
+int
+main (void)
+{
+  func1 ();
+  func2 ();
+}
diff --git a/gdb/testsuite/gdb.dwarf2/loclists-start-end.exp b/gdb/testsuite/gdb.dwarf2/loclists-start-end.exp
new file mode 100644
index 00000000000..43ddefcf61d
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/loclists-start-end.exp
@@ -0,0 +1,137 @@
+# Copyright 2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test support for DW_LLE_start_end (PR symtab/27999).
+
+load_lib dwarf.exp
+
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Test with 32-bit and 64-bit DWARF.
+foreach_with_prefix is_64 {false true} {
+    if { $is_64 } {
+	standard_testfile .c -dw64.S
+	set testfile ${testfile}-dw64
+    } else {
+	standard_testfile .c -dw32.S
+	set testfile ${testfile}-dw32
+    }
+
+    # Get the addresses / lengths of func1 and func2.
+    lassign [function_range func1 $srcdir/$subdir/$srcfile] func1_addr func1_len
+    lassign [function_range func2 $srcdir/$subdir/$srcfile] func2_addr func2_len
+
+    set asm_file [standard_output_file $srcfile2]
+    Dwarf::assemble $asm_file {
+	global func1_addr func1_len
+	global func2_addr func2_len
+	global is_64
+
+	# The CU uses the DW_FORM_loclistx form to refer to the .debug_loclists
+	# section.
+	cu {
+	    version 5
+	    is_64 $is_64
+	} {
+	    declare_labels int_type
+
+	    DW_TAG_compile_unit {
+		{DW_AT_loclists_base cu_table DW_FORM_sec_offset}
+	    } {
+		int_type: DW_TAG_base_type {
+		    {DW_AT_byte_size 4 DW_FORM_data1}
+		    {DW_AT_encoding @DW_ATE_signed}
+		    {DW_AT_name "int"}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name "foo"}
+		    {DW_AT_location 1 DW_FORM_loclistx}
+		    {DW_AT_type :$int_type}
+		}
+
+		DW_TAG_subprogram {
+		    {DW_AT_name "func1"}
+		    {DW_AT_low_pc $func1_addr}
+		    {DW_AT_high_pc $func1_len DW_FORM_udata}
+		}
+
+		DW_TAG_subprogram {
+		    {DW_AT_name "func2"}
+		    {DW_AT_low_pc $func2_addr}
+		    {DW_AT_high_pc $func2_len DW_FORM_udata}
+		}
+	    }
+	}
+
+	loclists -is-64 $is_64 {
+	    # This table is unused, but exists so that the used table is not at
+	    # the beginning of the section.
+	    table {
+		list_ {
+		    start_end 0x1000 0x2000 { DW_OP_addr 0x100000 }
+		}
+	    }
+
+	    # The lists in this table are accessed by index (DW_FORM_rnglistx).
+	    table -post-header-label cu_table {
+		# This list is unused, but exists to offset the next ones.
+		list_ {
+		    start_end 0x1000 0x2000 { DW_OP_addr 0x100000 }
+		}
+
+		# For variable foo.
+		list_ {
+		    # When in func1.
+		    start_end $func1_addr "$func1_addr + $func1_len" {
+			DW_OP_constu 0x123456
+			DW_OP_stack_value
+		    }
+
+		    # When in func2.
+		    start_end $func2_addr "$func2_addr + $func2_len" {
+			DW_OP_constu 0x234567
+			DW_OP_stack_value
+		    }
+		}
+	    }
+	}
+    }
+
+    if { [prepare_for_testing "failed to prepare" ${testfile} \
+	      [list $srcfile $asm_file] {nodebug}] } {
+	return -1
+    }
+
+    if { ![runto_main] } {
+	fail "can't run to main"
+	return
+    }
+
+    gdb_breakpoint "func1"
+    gdb_breakpoint "func2"
+
+    gdb_continue_to_breakpoint "func1"
+    with_test_prefix "at func1" {
+	gdb_test "print /x foo" " = 0x123456"
+    }
+
+    gdb_continue_to_breakpoint "func2"
+    with_test_prefix "at func2" {
+	gdb_test "print /x foo" " = 0x234567"
+    }
+}
diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index e4dc284f4ee..4e6879a2d3f 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -1849,6 +1849,35 @@ namespace eval Dwarf {
 		    incr _debug_loclists_locdesc_count
 		}
 
+		# Emit a DW_LLE_start_end entry.
+
+		proc start_end { start end locdesc } {
+		    variable _debug_loclists_is_64_dwarf
+		    variable _debug_loclists_addr_size
+		    variable _debug_loclists_offset_size
+		    variable _debug_loclists_table_count
+		    variable _debug_loclists_list_count
+		    variable _debug_loclists_locdesc_count
+
+		    _op .byte 0x07 "DW_LLE_start_end"
+
+		    # Start and end of the address range.
+		    _op .${_debug_loclists_addr_size}byte $start "start"
+		    _op .${_debug_loclists_addr_size}byte $end "end"
+
+		    # Length of location description.
+		    set locdesc_start_label ".Lloclists_table_${_debug_loclists_table_count}_list_${_debug_loclists_list_count}_locdesc_${_debug_loclists_locdesc_count}_start"
+		    set locdesc_end_label ".Lloclists_table_${_debug_loclists_table_count}_list_${_debug_loclists_list_count}_locdesc_${_debug_loclists_locdesc_count}_end"
+		    _op .uleb128 "$locdesc_end_label - $locdesc_start_label" "locdesc length"
+
+		    define_label $locdesc_start_label
+		    set dwarf_version 5
+		    _location $locdesc $dwarf_version $_debug_loclists_addr_size $_debug_loclists_offset_size
+		    define_label $locdesc_end_label
+
+		    incr _debug_loclists_locdesc_count
+		}
+
 		uplevel $body
 
 		# Emit end of list.
-- 
2.31.1

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: [PATCH] gdb: Support DW_LLE_start_end

[Simon Marchi]

On 2021-06-22 8:24 a.m., Andreas Schwab wrote:
> Without that it is impossible to debug on riscv64.
> 
> gdb/
> 	PR symtab/27999
> 	* dwarf2/loc.c (decode_debug_loclists_addresses): Support
> 	DW_LLE_start_end.
> 
> gdb/testsuite/
> 	PR symtab/27999
> 	* lib/dwarf.exp (start_end): New proc inside loclists.
> 	* gdb.dwarf2/loclists-start-end.exp: New file.
> 	* gdb.dwarf2/loclists-start-end.c: New file.

LGTM, thanks.

Simon