Re: [PATCH][gdb/symtab] Handle DW_AT_ranges with DW_FORM_sec_off in partial DIE

[Bernd Edlinger <bernd.edlinger@hotmail.de>]

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On 1/25/21 7:53 PM, Bernd Edlinger wrote:

> see attached patch.txt.

Oops, that patch.txt was incomplete.
please find the correct patch here.

> 
> It happens pretty reliably when you have a function that contains an error
> handling that looks obvously "unlinkely" to the compiler, because it is guarded

I meant, "obviously unlikely".

> by an if-condition and calls abort(), while there are also code paths that
> don't call about.  The parts that call abort are then in a separate cold section.
> 
> 
> Bernd.
> 

[-- Attachment #2: patch.txt --]
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diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index 7462890..aba4afb 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -473,7 +473,8 @@ namespace eval Dwarf {
 	    }
 
 	    DW_FORM_ref_udata -
-	    DW_FORM_udata {
+	    DW_FORM_udata -
+	    DW_FORM_rnglistx {
 		_op .uleb128 $value
 	    }
 
@@ -1115,8 +1116,16 @@ namespace eval Dwarf {
 	}
 	define_label $start_label
 	_op .2byte $_cu_version Version
-	_op .${_cu_offset_size}byte $my_abbrevs Abbrevs
-	_op .byte $_cu_addr_size "Pointer size"
+
+	# The CU header for DWARF 4 and 5 are slightly different.
+	if { $_cu_version == 5 } {
+	    _op .byte 0x1 "DW_UT_compile"
+	    _op .byte $_cu_addr_size "Pointer size"
+	    _op .${_cu_offset_size}byte $my_abbrevs Abbrevs
+	} else {
+	    _op .${_cu_offset_size}byte $my_abbrevs Abbrevs
+	    _op .byte $_cu_addr_size "Pointer size"
+	}
 
 	_defer_output $_abbrev_section {
 	    define_label $my_abbrevs
@@ -1306,6 +1315,178 @@ namespace eval Dwarf {
 	uplevel $body
     }
 
+    # Emit a DWARF .debug_rnglists section.
+    #
+    # The target address size is based on the current target's address size.
+    #
+    # There is one mandatory positional argument, BODY, which must be Tcl code
+    # that emits the content of the section.  It is evaluated in the caller's
+    # context.
+    #
+    # The following option can be used:
+    #
+    #  - -is-64 true|false: Whether to use 64-bit DWARF instead of 32-bit DWARF.
+    #                       The default is 32-bit.
+
+    proc rnglists { args } {
+	variable _debug_rnglists_addr_size
+	variable _debug_rnglists_offset_size
+	variable _debug_rnglists_is_64_dwarf
+
+	parse_args {{"is-64" "false"}}
+
+	if { [llength $args] != 1 } {
+	    error "rnglists proc expects one positional argument (body)"
+	}
+
+	lassign $args body
+
+	if [is_64_target] {
+	    set _debug_rnglists_addr_size 8
+	} else {
+	    set _debug_rnglists_addr_size 4
+	}
+
+	if { ${is-64} } {
+	    set _debug_rnglists_offset_size 8
+	    set _debug_rnglists_is_64_dwarf true
+	} else {
+	    set _debug_rnglists_offset_size 4
+	    set _debug_rnglists_is_64_dwarf false
+	}
+
+	_section ".debug_rnglists"
+
+	# Count of tables in the section.
+	variable _debug_rnglists_table_count 0
+
+	# Compute the label name for list at index LIST_IDX, for the current
+	# table.
+
+	proc _compute_list_label { list_idx } {
+	    variable _debug_rnglists_table_count
+
+	    return ".Lrnglists_table_${_debug_rnglists_table_count}_list_${list_idx}"
+	}
+
+	# Generate one table (header + offset array + range lists).
+	#
+	# Accepts one positional argument, BODY.  BODY may call the LIST_
+	# procedure to generate rnglists.
+	#
+	# The -post-header-label option can be used to define a label just after
+	# the header of the table.  This is the label that a DW_AT_rnglists_base
+	# attribute will usually refer to.
+
+	proc table { args } {
+	    variable _debug_rnglists_table_count
+	    variable _debug_rnglists_addr_size
+	    variable _debug_rnglists_offset_size
+	    variable _debug_rnglists_is_64_dwarf
+
+	    parse_args {{post-header-label ""}}
+
+	    if { [llength $args] != 1 } {
+		error "table proc expects one positional argument (body)"
+	    }
+
+	    lassign $args body
+
+	    # Generate one range list.
+	    #
+	    # BODY may call the various procs defined below to generate list entries.
+	    # They correspond to the range list entry kinds described in section 2.17.3
+	    # of the DWARF 5 spec.
+	    #
+	    # To define a label pointing to the beginning of the list, use
+	    # the conventional way of declaring and defining labels:
+	    #
+	    #   declare_labels the_list
+	    #
+	    #   the_list: list_ {
+	    #     ...
+	    #   }
+
+	    proc list_ { body } {
+		variable _debug_rnglists_list_count
+
+		# Define a label for this list.  It is used to build the offset
+		# array later.
+		set list_label [_compute_list_label $_debug_rnglists_list_count]
+		define_label $list_label
+
+		# Emit a DW_RLE_start_end entry.
+
+		proc start_end { start end } {
+		    variable _debug_rnglists_addr_size
+
+		    _op .byte 0x06 "DW_RLE_start_end"
+		    _op .${_debug_rnglists_addr_size}byte $start "start"
+		    _op .${_debug_rnglists_addr_size}byte $end "end"
+		}
+
+		uplevel $body
+
+		# Emit end of list.
+		_op .byte 0x00 "DW_RLE_end_of_list"
+
+		incr _debug_rnglists_list_count
+	    }
+
+	    # Count of lists in the table.
+	    variable _debug_rnglists_list_count 0
+
+	    # Generate the lists ops first, because we need to know how many
+	    # lists there are to generate the header and offset table.
+	    set lists_ops [_defer_to_string {
+		uplevel $body
+	    }]
+
+	    set post_unit_len_label \
+		[_compute_label "rnglists_table_${_debug_rnglists_table_count}_post_unit_len"]
+	    set post_header_label \
+		[_compute_label "rnglists_table_${_debug_rnglists_table_count}_post_header"]
+	    set table_end_label \
+		[_compute_label "rnglists_table_${_debug_rnglists_table_count}_end"]
+
+	    # Emit the table header.
+	    if { $_debug_rnglists_is_64_dwarf } {
+		_op .4byte 0xffffffff "unit length 1/2"
+		_op .8byte "$table_end_label - $post_unit_len_label" "unit length 2/2"
+	    } else {
+		_op .4byte "$table_end_label - $post_unit_len_label" "unit length"
+	    }
+
+	    define_label $post_unit_len_label
+
+	    _op .2byte 5 "dwarf version"
+	    _op .byte $_debug_rnglists_addr_size "address size"
+	    _op .byte 0 "segment selector size"
+	    _op .4byte "$_debug_rnglists_list_count" "offset entry count"
+
+	    define_label $post_header_label
+
+	    # Define the user post-header label, if provided.
+	    if { ${post-header-label} != "" } {
+		define_label ${post-header-label}
+	    }
+
+	    # Emit the offset array.
+	    for {set list_idx 0} {$list_idx < $_debug_rnglists_list_count} {incr list_idx} {
+		set list_label [_compute_list_label $list_idx]
+		_op .${_debug_rnglists_offset_size}byte "$list_label - $post_header_label" "offset of list $list_idx"
+	    }
+
+	    # Emit the actual list data.
+	    _emit "$lists_ops"
+
+	    define_label $table_end_label
+
+	    incr _debug_rnglists_table_count
+	}
+
+	uplevel $body
+    }
 
     # Emit a DWARF .debug_line unit.
     # OPTIONS is a list with an even number of elements containing
diff --git a/gdb/testsuite/gdb.dwarf2/rnglists-multiple-cus.exp b/gdb/testsuite/gdb.dwarf2/rnglists-multiple-cus.exp
new file mode 100644
index 0000000..e09cd4e
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/rnglists-multiple-cus.exp
@@ -0,0 +1,102 @@
+# Copyright 2020 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 to reproduce the crash described in PR 26813.
+#
+# When reading a list in any table in the .debug_rnglists section, GDB would
+# read the header at offset 0 in the section (the header of the first table).
+# When the index of the list we read was greater than the number of lists of
+# the first table, GDB would erroneously report that the index is invalid.
+#
+# So this test creates a .debug_rnglists section with two tables.  The second
+# table has more lists than the first one and we try to read a high index in
+# the second table.
+
+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 main.c -dw64.S
+	set testfile ${testfile}-dw64
+    } else {
+	standard_testfile main.c -dw32.S
+	set testfile ${testfile}-dw32
+    }
+
+    set asm_file [standard_output_file $srcfile2]
+    Dwarf::assemble $asm_file {
+	global is_64
+
+	# The CU uses the DW_FORM_rnglistx form to refer to the .debug_rnglists
+	# section.
+	cu {
+	    version 5
+	    is_64 $is_64
+	} {
+	    DW_TAG_compile_unit {
+		{DW_AT_ranges 1 DW_FORM_rnglistx}
+		{DW_AT_rnglists_base cu_table DW_FORM_sec_offset}
+	    } {
+		# This tests a DW_AT_ranges attribute of form DW_FORM_rnglistx on a
+		# function, which was buggy at some point.
+		DW_TAG_subprogram {
+		    {DW_AT_name "foo"}
+		    {DW_AT_ranges 2 DW_FORM_rnglistx}
+		}
+	    }
+	}
+
+	rnglists -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
+		}
+	    }
+
+	    # 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 0x2000 0x3000
+		}
+
+		# For the CU.
+		list_ {
+		    start_end 0x3000 0x4000
+		}
+
+		# For function foo.
+		list_ {
+		    start_end 0x3000 0x3010
+		}
+	    }
+	}
+    }
+
+    if { [prepare_for_testing "failed to prepare" ${testfile} \
+	      [list $srcfile $asm_file] {nodebug}] } {
+	return -1
+    }
+
+    # Sanity checks to make sure GDB slurped the symbols correctly.
+    gdb_test "p/x &foo" " = 0x3000"
+}
diff --git a/gdb/testsuite/gdb.dwarf2/rnglists-sec-offset.exp b/gdb/testsuite/gdb.dwarf2/rnglists-sec-offset.exp
new file mode 100644
index 0000000..d898d11
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/rnglists-sec-offset.exp
@@ -0,0 +1,80 @@
+# Copyright 2020 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 DW_AT_ranges attributes referencing the .debug_rnglists section using the
+# DW_FORM_sec_offset form.
+
+load_lib dwarf.exp
+
+if {![dwarf2_support]} {
+    return 0
+}
+
+foreach_with_prefix is_64 {false true} {
+    if { $is_64 } {
+	standard_testfile main.c -dw64.S
+	set testfile ${testfile}-dw64
+    } else {
+	standard_testfile main.c -dw32.S
+	set testfile ${testfile}-dw32
+    }
+
+    set asm_file [standard_output_file $srcfile2]
+    Dwarf::assemble $asm_file {
+	global is_64
+
+	declare_labels cu_range_list foo_range_list
+
+	# This CU uses the DW_FORM_sec_offset form to refer to the .debug_rnglists
+	# section.
+	cu {
+	    version 5
+	    is_64 $is_64
+	} {
+	    DW_TAG_compile_unit {
+		{DW_AT_ranges $cu_range_list DW_FORM_sec_offset}
+	    } {
+		DW_TAG_subprogram {
+		    {DW_AT_name "foo"}
+		    {DW_AT_ranges $foo_range_list DW_FORM_sec_offset}
+		}
+	    }
+	}
+
+	rnglists -is-64 $is_64 {
+	    # The lists in this table are accessed by direct offset
+	    # (DW_FORM_sec_offset).
+	    table {
+		# For the CU.
+		cu_range_list: list_ {
+		    start_end 0x4000 0x5000
+		}
+
+		# For function foo.
+		foo_range_list: list_ {
+		    start_end 0x4000 0x4010
+		}
+	    }
+	}
+    }
+
+    if { [prepare_for_testing "failed to prepare" ${testfile} \
+	      [list $srcfile $asm_file] {nodebug}] } {
+	return -1
+    }
+
+    # Sanity checks to make sure GDB slurped the symbols correctly.
+    gdb_test "p/x &foo" " = 0x4000"
+}