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author | Patrick Palka <patrick@parcs.ath.cx> | 2014-09-16 17:40:06 +0100 |
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committer | Pedro Alves <palves@redhat.com> | 2014-09-16 17:40:06 +0100 |
commit | bb9d5f81c36ecc61e3d4a70ce7e41348c8b12fef (patch) | |
tree | 87ce6907cc01910723e151cd42f08414548d7d64 /gdb/value.h | |
parent | d3d3c6db1a3de87d5df6900f3be0557c33fa23b3 (diff) | |
download | binutils-bb9d5f81c36ecc61e3d4a70ce7e41348c8b12fef.zip binutils-bb9d5f81c36ecc61e3d4a70ce7e41348c8b12fef.tar.gz binutils-bb9d5f81c36ecc61e3d4a70ce7e41348c8b12fef.tar.bz2 |
Fix PR12526: -location watchpoints for bitfield arguments
PR 12526 reports that -location watchpoints against bitfield arguments
trigger false positives when bits around the bitfield, but not the
bitfield itself, are modified.
This happens because -location watchpoints naturally operate at the
byte level, not at the bit level. When the address of a bitfield
lvalue is taken, information about the bitfield (i.e. its offset and
size) is lost in the process.
This information must first be retained throughout the lifetime of the
-location watchpoint. This patch achieves this by adding two new
fields to the watchpoint struct: val_bitpos and val_bitsize. These
fields are set when a watchpoint is first defined in watch_command_1.
They are both equal to zero if the watchpoint is not a -location
watchpoint or if the argument is not a bitfield.
Then these bitfield parameters are used inside update_watchpoint and
watchpoint_check to extract the actual value of the bitfield from the
watchpoint address, with the help of a local helper function
extract_bitfield_from_watchpoint_value.
Finally when creating a HW breakpoint pointing to a bitfield, we
optimize the address and length of the breakpoint. By skipping over
the bytes that don't cover the bitfield, this step reduces the
frequency at which a read watchpoint for the bitfield is triggered.
It also reduces the number of times a false-positive call to
check_watchpoint is triggered for a write watchpoint.
gdb/
PR breakpoints/12526
* breakpoint.h (struct watchpoint): New fields val_bitpos and
val_bitsize.
* breakpoint.c (watch_command_1): Use these fields to retain
bitfield information.
(extract_bitfield_from_watchpoint_value): New function.
(watchpoint_check): Use it.
(update_watchpoint): Use it. Optimize the address and length of a
HW watchpoint pointing to a bitfield.
* value.h (unpack_value_bitfield): New prototype.
* value.c (unpack_value_bitfield): Make extern.
gdb/testsuite/
PR breakpoints/12526
* gdb.base/watch-bitfields.exp: New file.
* gdb.base/watch-bitfields.c: New file.
Diffstat (limited to 'gdb/value.h')
-rw-r--r-- | gdb/value.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/gdb/value.h b/gdb/value.h index 4cdbf21..e3603c3 100644 --- a/gdb/value.h +++ b/gdb/value.h @@ -613,6 +613,11 @@ extern int unpack_value_field_as_long (struct type *type, const gdb_byte *valadd int embedded_offset, int fieldno, const struct value *val, LONGEST *result); +extern void unpack_value_bitfield (struct value *dest_val, + int bitpos, int bitsize, + const gdb_byte *valaddr, int embedded_offset, + const struct value *val); + extern struct value *value_field_bitfield (struct type *type, int fieldno, const gdb_byte *valaddr, int embedded_offset, |