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Commit 9a03f218 ("Fix gdb.base/watchpoint-unaligned.exp on aarch64")
fixed a watchpoint bug in gdb -- but did not touch the corresponding
code in gdbserver.
This patch moves the gdb code into gdb/nat, so that it can be shared
with gdbserver, and then changes gdbserver to use it, fixing the bug.
This is yet another case where having a single back end would prevent
bugs.
I tested this using the AdaCore internal gdb testsuite.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29423
Approved-By: Luis Machado <luis.machado@arm.com>
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Now that defs.h, server.h and common-defs.h are included via the
`-include` option, it is no longer necessary for source files to include
them. Remove all the inclusions of these files I could find. Update
the generation scripts where relevant.
Change-Id: Ia026cff269c1b7ae7386dd3619bc9bb6a5332837
Approved-By: Pedro Alves <pedro@palves.net>
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On aarch64-linux, with test-case gdb.base/watchpoint-unaligned.exp I run into:
...
(gdb) watch data.u.size8twice[1]^M
Hardware watchpoint 241: data.u.size8twice[1]^M
(gdb) PASS: gdb.base/watchpoint-unaligned.exp: watch data.u.size8twice[1]
continue^M
Continuing.^M
FAIL: gdb.base/watchpoint-unaligned.exp: continue (timeout)
FAIL: gdb.base/watchpoint-unaligned.exp: size8twice write
...
This happens as follows.
We start the exec and set an 8-byte hardware watchpoint on
data.u.size8twice[1] at address 0x440048:
...
(gdb) p sizeof (data.u.size8twice[1])
$1 = 8
(gdb) p &data.u.size8twice[1]
$2 = (uint64_t *) 0x440048 <data+16>
...
We continue execution, and a 16-byte write at address 0x440040 triggers the
hardware watchpoint:
...
4101c8: a9000801 stp x1, x2, [x0]
...
When checking whether a watchpoint has triggered in
aarch64_stopped_data_address, we check against address 0x440040 (passed in
parameter addr_trap). This behaviour is documented:
...
/* ADDR_TRAP reports the first address of the memory range
accessed by the CPU, regardless of what was the memory
range watched. ... */
...
and consequently the matching logic compares against an addr_watch_aligned:
...
&& addr_trap >= addr_watch_aligned
&& addr_trap < addr_watch + len)
...
However, the comparison fails:
...
(gdb) p /x addr_watch_aligned
$3 = 0x440048
(gdb) p addr_trap >= addr_watch_aligned
$4 = false
...
Consequently, aarch64_stopped_data_address returns false, and
stopped_by_watchpoint returns false, and watchpoints_triggered returns 0,
which make infrun think it's looking at a delayed hardware
breakpoint/watchpoint trap:
...
[infrun] handle_signal_stop: stop_pc=0x4101c8
[infrun] handle_signal_stop: delayed hardware breakpoint/watchpoint trap, ignoring
...
Infrun then ignores the trap and continues, but runs into the same situation
again and again, causing a hang which then causes the test timeout.
Fix this by allowing a match 8 bytes below addr_watch_aligned. This
introduces the possibility for false positives, so we only do this for regular
"value changed" watchpoints.
An earlier version of this patch worked by aligning addr_watch_aligned to 16
instead of 8:
...
- const CORE_ADDR addr_watch_aligned = align_down (state->dr_addr_wp[i], 8);
+ const CORE_ADDR addr_watch_aligned = align_down (state->dr_addr_wp[i], 16);
...
but while that fixed the test-case, it didn't fix the problem completely, so
extend the test-case to check more scenarios.
Tested on aarch64-linux.
Tested-By: Luis Machado <luis.machado@arm.com>
Approved-By: Luis Machado <luis.machado@arm.com>
PR tdep/29423
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29423
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On aarch64-linux, with test-case gdb.base/watch-bitfields.exp I run into:
...
(gdb) continue^M
Continuing.^M
^M
Hardware watchpoint 2: -location q.a^M
^M
Old value = 1^M
New value = 0^M
main () at watch-bitfields.c:42^M
42 q.h--;^M
(gdb) FAIL: $exp: -location watch against bitfields: q.e: 0->5: continue
...
In a minimal form, if we step past line 37 which sets q.e, and we have a
watchpoint set on q.e, it triggers:
...
$ gdb -q -batch watch-bitfields -ex "b 37" -ex run -ex "watch q.e" -ex step
Breakpoint 1 at 0x410204: file watch-bitfields.c, line 37.
Breakpoint 1, main () at watch-bitfields.c:37
37 q.e = 5;
Hardware watchpoint 2: q.e
Hardware watchpoint 2: q.e
Old value = 0
New value = 5
main () at /home/vries/gdb/src/gdb/testsuite/gdb.base/watch-bitfields.c:38
38 q.f = 6;
...
However, if we set in addition a watchpoint on q.a, the watchpoint on q.e
doesn't trigger.
How does this happen?
Bitfield q.a is just bit 0 of byte 0, and bitfield q.e is bit 4..7 of byte 1
and bit 1 of byte 2. So, watch q.a should watch byte 0, and watch q.e should
watch bytes 1 and 2.
Using "maint set show-debug-regs on" (and some more detailed debug prints) we
get:
...
WP2: addr=0x440028 (orig=0x440029), ctrl=0x000000d5, ref.count=1
ctrl: enabled=1, offset=1, len=2
WP3: addr=0x440028 (orig=0x440028), ctrl=0x00000035, ref.count=1
ctrl: enabled=1, offset=0, len=1
...
which matches that.
When executing line 37, a hardware watchpoint trap triggers and we hit
aarch64_stopped_data_address with addr_trap == 0x440028:
...
(gdb) p /x addr_trap
$1 = 0x440028
....
and since the loop in aarch64_stopped_data_address walks backward, we check
WP3 first, which matches, and consequently target_stopped_by_watchpoint
returns true in watchpoints_triggered.
Likewise for target_stopped_data_address, which also returns addr == 0x440028.
Watchpoints_triggered matches watchpoint q.a to that address, and sets
watch_triggered_yes.
However, subsequently the value of q.a is checked, and it's the same value as
before (becase the insn in line 37 didn't change q.a), so the watchpoint
hardware trap is not reported to the user.
The problem originates from that fact that aarch64_stopped_data_address picked
WP3 instead of WP2.
There's something we can do about this. In the example above, both
target_stopped_by_watchpoint and target_stopped_data_address returned true.
Instead we can return true in target_stopped_by_watchpoint but false in
target_stopped_data_address. This lets watchpoints_triggered known that a
watchpoint was triggered, but we don't know where, and both watchpoints
get set to watch_triggered_unknown.
Subsequently, the values of both q.a and q.e are checked, and since q.e is not
the same value as before, the watchpoint hardware trap is reported to the user.
Note that this works well for regular (write) watchpoints (watch command), but
not for read watchpoints (rwatch command), because for those no value is
checked. Likewise for access watchpoints (awatch command).
So, fix this by:
- passing a nullptr in aarch64_fbsd_nat_target::stopped_by_watchpoint and
aarch64_linux_nat_target::stopped_by_watchpoint to make clear we're not
interested in the stop address,
- introducing a two-phase approach in aarch64_stopped_data_address, where:
- phase one handles access and read watchpoints, as before, and
- phase two handles write watchpoints, where multiple matches cause:
- return true if addr_p == null, and
- return false if addr_p != null.
Tested on aarch64-linux.
Approved-By: Luis Machado <luis.machado@arm.com>
PR tdep/31214
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31214
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This commit is the result of the following actions:
- Running gdb/copyright.py to update all of the copyright headers to
include 2024,
- Manually updating a few files the copyright.py script told me to
update, these files had copyright headers embedded within the
file,
- Regenerating gdbsupport/Makefile.in to refresh it's copyright
date,
- Using grep to find other files that still mentioned 2023. If
these files were updated last year from 2022 to 2023 then I've
updated them this year to 2024.
I'm sure I've probably missed some dates. Feel free to fix them up as
you spot them.
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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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Luis pointed out that I missed a spot in the gdb_printf conversion --
namely aarch64-nat.c. While looking at this, I found another spot in
darwin-nat.c that I also missed. I can't build either of these, but I
think this patch should fix the problems.
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This class includes platform-independent target methods for hardware
breakpoints and watchpoints using routines from
nat/aarch64-hw-point.c.
stopped_data_address is not platform-independent since the FAR
register holding the address for a breakpoint hit must be fetched in a
platform-specific manner. However, aarch64_stopped_data_address is
provided as a helper routine which performs platform-independent
validation given the value of the FAR register.
For tracking the per-process debug register mirror state, use an
unordered_map indexed by pid as recently adopted in x86-nat.c rather
than a manual linked-list.
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