From 4c55e9702527b73ff301e5c06f2055a606348de1 Mon Sep 17 00:00:00 2001 From: Tankut Baris Aktemur Date: Thu, 30 Jul 2020 19:23:38 +0200 Subject: [PATCH] gdb/breakpoint: set the condition exp after parsing the condition successfully In 'set_breakpoint_condition', GDB resets the condition expressions before parsing the condition input by the user. This leads to the problem of losing the condition expressions if the new condition does not parse successfully and is thus rejected. For instance: $ gdb ./test Reading symbols from ./test... (gdb) start Temporary breakpoint 1 at 0x114e: file test.c, line 4. Starting program: test Temporary breakpoint 1, main () at test.c:4 4 int a = 10; (gdb) break 5 Breakpoint 2 at 0x555555555155: file test.c, line 5. Now define a condition that would evaluate to false. Next, attempt to overwrite that with an invalid condition: (gdb) cond 2 a == 999 (gdb) cond 2 gibberish No symbol "gibberish" in current context. (gdb) info breakpoints Num Type Disp Enb Address What 2 breakpoint keep y 0x0000555555555155 in main at test.c:5 stop only if a == 999 It appears as if the bad condition is successfully rejected. But if we resume the program, we see that we hit the breakpoint although the condition would evaluate to false. (gdb) continue Continuing. Breakpoint 2, main () at test.c:5 5 a = a + 1; /* break-here */ Fix the problem by not resetting the condition expressions before parsing the condition input. Suppose the fix is applied. A similar problem could occur if the condition is valid, but has "junk" at the end. In this case, parsing succeeds, but an error is raised immediately after. It is too late, though; the condition expression is already updated. For instance: $ gdb ./test Reading symbols from ./test... (gdb) start Temporary breakpoint 1 at 0x114e: file test.c, line 4. Starting program: test Temporary breakpoint 1, main () at test.c:4 4 int a = 10; (gdb) break 5 Breakpoint 2 at 0x555555555155: file test.c, line 5. (gdb) cond 2 a == 999 (gdb) cond 2 a == 10 if Junk at end of expression (gdb) info breakpoints Num Type Disp Enb Address What 2 breakpoint keep y 0x0000555555555155 in main at test.c:5 stop only if a == 999 (gdb) c Continuing. Breakpoint 2, main () at test.c:5 5 a = a + 1; /* break-here */ (gdb) We should not have hit the breakpoint because the condition would evaluate to false. Fix this problem by updating the condition expression of the breakpoint after parsing the input successfully and checking that there is no remaining junk. gdb/ChangeLog: 2020-07-30 Tankut Baris Aktemur * breakpoint.c (set_breakpoint_condition): Update the condition expressions after checking that the input condition string parses successfully and does not contain junk at the end. gdb/testsuite/ChangeLog: 2020-07-30 Tankut Baris Aktemur * gdb.base/condbreak-bad.exp: Extend the test with scenarios that attempt to overwrite an existing condition with a condition that fails parsing and also with a condition that parses fine but contains junk at the end. --- gdb/ChangeLog | 6 ++ gdb/breakpoint.c | 59 ++++++++++------ gdb/testsuite/ChangeLog | 7 ++ gdb/testsuite/gdb.base/condbreak-bad.exp | 88 ++++++++++++++++++++++++ 4 files changed, 139 insertions(+), 21 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index cbe850d4681..cfc5b6db5f2 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2020-07-30 Tankut Baris Aktemur + + * breakpoint.c (set_breakpoint_condition): Update the condition + expressions after checking that the input condition string parses + successfully and does not contain junk at the end. + 2020-07-30 Tankut Baris Aktemur * breakpoint.c (set_breakpoint_condition): Update the diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c index a3a7c17fbcf..7e020c5f666 100644 --- a/gdb/breakpoint.c +++ b/gdb/breakpoint.c @@ -834,30 +834,30 @@ void set_breakpoint_condition (struct breakpoint *b, const char *exp, int from_tty) { - if (is_watchpoint (b)) - { - struct watchpoint *w = (struct watchpoint *) b; - - w->cond_exp.reset (); - } - else + if (*exp == 0) { - struct bp_location *loc; + xfree (b->cond_string); + b->cond_string = nullptr; - for (loc = b->loc; loc; loc = loc->next) + if (is_watchpoint (b)) { - loc->cond.reset (); + struct watchpoint *w = (struct watchpoint *) b; - /* No need to free the condition agent expression - bytecode (if we have one). We will handle this - when we go through update_global_location_list. */ + w->cond_exp.reset (); } - } + else + { + struct bp_location *loc; - if (*exp == 0) - { - xfree (b->cond_string); - b->cond_string = nullptr; + for (loc = b->loc; loc; loc = loc->next) + { + loc->cond.reset (); + + /* No need to free the condition agent expression + bytecode (if we have one). We will handle this + when we go through update_global_location_list. */ + } + } if (from_tty) printf_filtered (_("Breakpoint %d now unconditional.\n"), b->number); @@ -872,23 +872,40 @@ set_breakpoint_condition (struct breakpoint *b, const char *exp, innermost_block_tracker tracker; arg = exp; - w->cond_exp = parse_exp_1 (&arg, 0, 0, 0, &tracker); + expression_up new_exp = parse_exp_1 (&arg, 0, 0, 0, &tracker); if (*arg) error (_("Junk at end of expression")); + w->cond_exp = std::move (new_exp); w->cond_exp_valid_block = tracker.block (); } else { struct bp_location *loc; + /* Parse and set condition expressions. We make two passes. + In the first, we parse the condition string to see if it + is valid in all locations. If so, the condition would be + accepted. So we go ahead and set the locations' + conditions. In case a failing case is found, we throw + the error and the condition string will be rejected. + This two-pass approach is taken to avoid setting the + state of locations in case of a reject. */ + for (loc = b->loc; loc; loc = loc->next) + { + arg = exp; + parse_exp_1 (&arg, loc->address, + block_for_pc (loc->address), 0); + if (*arg != 0) + error (_("Junk at end of expression")); + } + + /* If we reach here, the condition is valid at all locations. */ for (loc = b->loc; loc; loc = loc->next) { arg = exp; loc->cond = parse_exp_1 (&arg, loc->address, block_for_pc (loc->address), 0); - if (*arg) - error (_("Junk at end of expression")); } } diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 7be030343bc..2a194d16fb6 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,10 @@ +2020-07-30 Tankut Baris Aktemur + + * gdb.base/condbreak-bad.exp: Extend the test with scenarios + that attempt to overwrite an existing condition with a condition + that fails parsing and also with a condition that parses fine + but contains junk at the end. + 2020-07-30 Tankut Baris Aktemur * gdb.base/condbreak-bad.c: New test. diff --git a/gdb/testsuite/gdb.base/condbreak-bad.exp b/gdb/testsuite/gdb.base/condbreak-bad.exp index a01ba2a9340..84d32a0f15d 100644 --- a/gdb/testsuite/gdb.base/condbreak-bad.exp +++ b/gdb/testsuite/gdb.base/condbreak-bad.exp @@ -38,3 +38,91 @@ gdb_test "info break" \ "${decimal}${fill}breakpoint${fill}keep y${fill}:${bp_location}"] \ "breakpoint is unconditional" +# Now define a valid condition. Attempt to override that with a 'bad' +# condition again. The condition should be preserved. +with_test_prefix "with run" { + gdb_test_no_output "cond $bpnum a == 10" + + gdb_test "cond $bpnum gibberish" \ + "No symbol \"gibberish\" in current context." \ + "attempt a bad condition" + + gdb_test "info break" \ + [multi_line \ + "Num${fill}What" \ + "${decimal}${fill}breakpoint${fill}keep y${fill}:${bp_location}" \ + "${fill}stop only if a == 10${fill}"] \ + "breakpoint condition is preserved" + + # Run the code. We should hit the breakpoint, because the + # condition evaluates to true. + + gdb_run_cmd + gdb_test "" ".*reakpoint .*, main .*${srcfile}.*" "run to the bp" +} + +# Restart. Repeat the test above after the program has started. +# This is needed to check a scenario where the breakpoints are no +# longer re-inserted due to solib events. Note that runto_main +# deletes the breakpoints. +with_test_prefix "with continue 1" { + if {![runto_main]} { + fail "could not run to main" + return -1 + } + + gdb_breakpoint "$bp_location" + set bpnum [get_integer_valueof "\$bpnum" 0 "get bpnum"] + + gdb_test_no_output "cond $bpnum a == 10" + + gdb_test "cond $bpnum gibberish" \ + "No symbol \"gibberish\" in current context." \ + "attempt a bad condition" + + # Resume. We should hit the breakpoint, because the + # condition evaluates to true. + gdb_continue_to_breakpoint "${srcfile}:${bp_location}" +} + +# Repeat with a condition that evaluates to false. +with_test_prefix "with continue 2" { + if {![runto_main]} { + fail "could not run to main" + return -1 + } + + gdb_breakpoint "$bp_location" + set bpnum [get_integer_valueof "\$bpnum" 0 "get bpnum"] + + gdb_test_no_output "cond $bpnum a == 999" + + gdb_test "cond $bpnum gibberish" \ + "No symbol \"gibberish\" in current context." \ + "attempt a bad condition" + + # Resume. We should *not* hit the breakpoint, because the + # condition evaluates to false. + gdb_continue_to_end +} + +# Repeat with a condition that contains junk at the end. +with_test_prefix "with junk" { + if {![runto_main]} { + fail "could not run to main" + return -1 + } + + gdb_breakpoint "$bp_location" + set bpnum [get_integer_valueof "\$bpnum" 0 "get bpnum"] + + gdb_test_no_output "cond $bpnum a == 999" + + gdb_test "cond $bpnum a == 10 if" \ + "Junk at end of expression" \ + "attempt a bad condition" + + # Resume. We should *not* hit the breakpoint, because the + # condition evaluates to false. + gdb_continue_to_end +} -- 2.30.2