[PATCH] Harden gdb.base/bp-permanent.exp

Luis Machado
2015-04-09T17:11:07Z

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This testcase does not work as expected in QEMU (aarch64 QEMU in my
case). It fails when trying to manually write the breakpoint instruction
to a certain PC address.

(gdb) p /x addr_bp[0] = buffer[0]^M
Cannot access memory at address 0x400834^M
(gdb) PASS: gdb.base/bp-permanent.exp: always_inserted=off,
sw_watchpoint=0: setup: p /x addr_bp[0] = buffer[0]
p /x addr_bp[1] = buffer[1]^M
Cannot access memory at address 0x400835^M
(gdb) PASS: gdb.base/bp-permanent.exp: always_inserted=off,
sw_watchpoint=0: setup: p /x addr_bp[1] = buffer[1]
p /x addr_bp[2] = buffer[2]^M
Cannot access memory at address 0x400836^M
(gdb) PASS: gdb.base/bp-permanent.exp: always_inserted=off,
sw_watchpoint=0: setup: p /x addr_bp[2] = buffer[2]
p /x addr_bp[3] = buffer[3]^M
Cannot access memory at address 0x400837^M
(gdb) PASS: gdb.base/bp-permanent.exp: always_inserted=off,
sw_watchpoint=0: setup: p /x addr_bp[3] = buffer[3]

The following patch prevents a number of failures by detecting this and
bailing out in case the target has such a restriction. Writing to .text
from within the program isn't any better. It just leads to a SIGSEGV.

Before the patch:

=== gdb Summary ===

# of expected passes 66
# of unexpected failures 56

After the patch:

=== gdb Summary ===

# of expected passes 26
# of unsupported tests 4

I regtested this on x86-64 and it still works fine.

Ok?

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2015-04-09 Luis Machado <lgustavo@codesourcery.com>

gdb/testsuite/
* gdb.base/bp-permanent.exp (test): Handle the case of being unable
to write to the .text section.

diff --git a/gdb/testsuite/gdb.base/bp-permanent.exp b/gdb/testsuite/gdb.base/bp-permanent.exp
index 81a5293..9193db8 100644
--- a/gdb/testsuite/gdb.base/bp-permanent.exp
+++ b/gdb/testsuite/gdb.base/bp-permanent.exp
@@ -104,7 +104,18 @@ proc test {always_inserted sw_watchpoint} {
# to memory manually.
set count [expr $address_after_bp - $address_bp]
for {set i 0} {$i < $count} {incr i} {
- gdb_test "p /x addr_bp\[$i\] = buffer\[$i\]" " = .*"
+ gdb_test_multiple "p /x addr_bp\[$i\] = buffer\[$i\]" $test {
+ -re "Cannot access memory at address $hex.*$gdb_prompt $" {
+ # Some targets (QEMU for one) do not allow writes to the
+ # .text section. It is no use continuing with the test
+ # at this point. Just return.
+ unsupported $test
+ return
+ }
+ -re " = .*$gdb_prompt $" {
+ pass $test
+ }
+ }
}
}