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Correctly handle DW_LLE_start_end

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When the code to handle DW_LLE_start_end was added (as part of some
DWARF 5 work), it was written to add the base address.  However, this
seems incorrect -- the DWARF standard describes this as an address,
not an offset from the base address.

This patch changes a couple of spots in dwarf2/loc.c to fix this
problem.  It then changes decode_debug_loc_addresses to return
DEBUG_LOC_OFFSET_PAIR instead, which preserves the previous semantics.

This only showed up on the RISC-V target internally, due to the
combination of DWARF 5 and a newer version of GCC.  I've updated a
couple of existing loclists test cases to demonstrate the bug.
This commit is contained in:
Tom Tromey 2021-11-08 10:58:27 -07:00
parent 0b03c6f03d
commit 7b9f73fad0
4 changed files with 30 additions and 7 deletions
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17
gdb/dwarf2/loc.c
View file

@ -139,7 +139,9 @@ decode_debug_loc_addresses (const gdb_byte *loc_ptr, const gdb_byte *buf_end,
if (*low == 0 && *high == 0)
return DEBUG_LOC_END_OF_LIST;
return DEBUG_LOC_START_END;
/* We want the caller to apply the base address, so we must return
DEBUG_LOC_OFFSET_PAIR here. */
return DEBUG_LOC_OFFSET_PAIR;
}
/* Decode the addresses in .debug_loclists entry.
@ -416,13 +418,15 @@ dwarf2_find_location_expression (struct dwarf2_loclist_baton *baton,
.debug_addr which already has the DWARF "base address". We still add
base_offset in case we're debugging a PIE executable. However, if the
entry is DW_LLE_offset_pair from a DWO, add the base address as the
operands are offsets relative to the applicable base address. */
operands are offsets relative to the applicable base address.
If the entry is DW_LLE_start_end or DW_LLE_start_length, then
it already is an address, and we don't need to add the base. */
if (baton->from_dwo && kind != DEBUG_LOC_OFFSET_PAIR)
{
low += base_offset;
high += base_offset;
}
else
else if (kind == DEBUG_LOC_OFFSET_PAIR)
{
low += base_address;
high += base_address;
@ -3983,8 +3987,11 @@ loclist_describe_location (struct symbol *symbol, CORE_ADDR addr,
}
/* Otherwise, a location expression entry. */
low += base_address;
high += base_address;
if (kind == DEBUG_LOC_OFFSET_PAIR)
{
low += base_address;
high += base_address;
}
low = gdbarch_adjust_dwarf2_addr (gdbarch, low);
high = gdbarch_adjust_dwarf2_addr (gdbarch, high);

5
gdb/testsuite/gdb.dwarf2/loclists-multiple-cus.exp
View file

@ -1,4 +1,4 @@
# Copyright 2020 Free Software Foundation, Inc.
# Copyright 2020, 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
@ -105,6 +105,9 @@ foreach_with_prefix is_64 {false true} {
# For variable foo.
list_ {
# This should not affect the following addresses.
base_address 0xffff
# When in func1.
start_length $func1_addr $func1_len {
DW_OP_constu 0x123456

3
gdb/testsuite/gdb.dwarf2/loclists-start-end.exp
View file

@ -96,6 +96,9 @@ foreach_with_prefix is_64 {false true} {
# For variable foo.
list_ {
# This should not affect the following addresses.
base_address 0xffff
# When in func1.
start_end $func1_addr "$func1_addr + $func1_len" {
DW_OP_constu 0x123456

12
gdb/testsuite/lib/dwarf.exp
View file

@ -1894,9 +1894,10 @@ namespace eval Dwarf {
define_label $list_label
with_override Dwarf::start_length Dwarf::_loclists_start_length {
with_override Dwarf::base_address Dwarf::_loclists_base_address {
with_override Dwarf::start_end Dwarf::_loclists_start_end {
uplevel $body
}}
}}}
# Emit end of list.
_op .byte 0x00 "DW_LLE_end_of_list"
@ -1972,6 +1973,15 @@ namespace eval Dwarf {
incr _debug_loclists_locdesc_count
}
# Emit a DW_LLE_base_address entry.
proc _loclists_base_address {addr} {
variable _debug_loclists_addr_size
variable _debug_loclists_locdesc_count
_op .byte 0x06 "DW_LLE_base_address"
_op .${_debug_loclists_addr_size}byte $addr "base_address"
incr _debug_loclists_locdesc_count
}
# Emit a DWARF .debug_line unit.
# OPTIONS is a list with an even number of elements containing
# option-name and option-value pairs.