bdde90c4ce
We recently realized that symbol_needs_eval_fail.exp and
symbol_needs_eval_timeout.exp invalidly dereference an int (4 bytes on
x86_64) by reading 8 bytes (the size of a pointer).
Here how it goes:
In gdb/testsuite/gdb.dwarf2/symbol_needs_eval.c a global variable is
defined:
int exec_mask = 1;
and later both tests build some DWARF using the assembler doing:
set exec_mask_var [gdb_target_symbol exec_mask]
...
DW_TAG_variable {
{DW_AT_name a}
{DW_AT_type :$int_type_label}
{DW_AT_location {
DW_OP_addr $exec_mask_var
DW_OP_deref
...
}
}
The definition of the DW_OP_deref (from Dwarf5 2.5.1.3 Stack Operations)
says that "The size of the data retrieved from the dereferenced address
is the size of an address on the target machine."
On x86_64, the size of an int is 4 while the size of an address is 8.
The result is that when evaluating this expression, the debugger reads
outside of the `a` variable.
Fix this by using `DW_OP_deref_size $int_size` instead. To achieve
this, this patch adds the necessary steps so we can figure out what
`sizeof(int)` evaluates to for the current target.
While at it, also change the definition of the int type in the assembled
DWARF information so we use the actual target's size for an int instead
of the literal 4.
Tested on x86_64 Linux.
Approved-By: Tom Tromey <tom@tromey.com>
135 lines
3.3 KiB
Text
135 lines
3.3 KiB
Text
# Copyright 2017-2023 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Test the symbol needs check mechanism if it assumes that faking
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# reads from a target is a safe thing to do.
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#
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# In particular, the test uses a relative branch DWARF operation to
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# potentially cause an infinite loop, if the target reads are indeed
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# faked.
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-2 and use gas.
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require dwarf2_support
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# Choose suitable integer registers for the test.
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set dwarf_regnum 0
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if { [is_aarch64_target] } {
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set regname x0
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} elseif { [is_aarch32_target]
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|| [istarget "s390*-*-*" ]
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|| [istarget "powerpc*-*-*"]
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|| [istarget "rs6000*-*-aix*"] } {
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set regname r0
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} elseif { [is_x86_like_target] } {
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set regname eax
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} elseif { [is_amd64_regs_target] } {
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set regname rax
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} else {
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verbose "Skipping ${gdb_test_file_name}."
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return
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}
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standard_testfile symbol_needs_eval.c ${gdb_test_file_name}-dw.S
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if [prepare_for_testing "failed to prepare" $testfile $srcfile {debug}] {
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return
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}
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set int_size [get_sizeof "int" -1]
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# Make some DWARF for the test.
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set asm_file [standard_output_file $srcfile2]
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Dwarf::assemble $asm_file {
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global dwarf_regnum regname int_size
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set exec_mask_var [gdb_target_symbol exec_mask]
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cu {} {
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DW_TAG_compile_unit {
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{DW_AT_name symbol_needs_eval.c}
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{DW_AT_comp_dir /tmp}
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} {
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declare_labels int_type_label
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# define int type
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int_type_label: DW_TAG_base_type {
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{DW_AT_name "int"}
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{DW_AT_encoding @DW_ATE_signed}
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{DW_AT_byte_size $int_size DW_FORM_sdata}
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}
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# add info for variable exec_mask
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DW_TAG_variable {
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{DW_AT_name exec_mask}
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{DW_AT_type :$int_type_label}
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{DW_AT_location {
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DW_OP_addr $exec_mask_var
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} SPECIAL_expr}
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{external 1 flag}
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}
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# add info for subprogram main
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DW_TAG_subprogram {
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{MACRO_AT_func { main }}
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{DW_AT_frame_base {
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DW_OP_regx $dwarf_regnum
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} SPECIAL_expr}
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} {
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# define artificial variable a
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DW_TAG_variable {
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{DW_AT_name a}
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{DW_AT_type :$int_type_label}
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{DW_AT_location {
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DW_OP_lit1
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DW_OP_addr $exec_mask_var
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DW_OP_deref_size $int_size
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# jump to DW_OP_fbreg
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DW_OP_skip 4
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DW_OP_drop
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DW_OP_fbreg 0
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DW_OP_dup
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DW_OP_lit0
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DW_OP_eq
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# conditional jump to DW_OP_drop
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DW_OP_bra -9
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DW_OP_stack_value
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} SPECIAL_expr}
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{external 1 flag}
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}
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}
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}
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}
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}
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if { [prepare_for_testing ${testfile}.exp ${testfile} \
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[list $srcfile $asm_file] {nodebug}] } {
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return -1
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}
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if ![runto_main] {
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return -1
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}
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gdb_test_no_output "set var \$$regname = 2" "init reg to 2"
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gdb_test_no_output "set var exec_mask = 0" "init exec_mask to 0"
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gdb_test "print/d a" " = 2" "a == 2"
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