[gdb/python] Make gdb.UnwindInfo.add_saved_register more robust
Checks
| Context |
Check |
Description |
| linaro-tcwg-bot/tcwg_gdb_build--master-aarch64 |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_build--master-arm |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_check--master-arm |
success
|
Testing passed
|
| linaro-tcwg-bot/tcwg_gdb_check--master-aarch64 |
success
|
Testing passed
|
Commit Message
On arm-linux, until commit bbb12eb9c84 ("gdb/arm: Remove tpidruro register
from non-FreeBSD target descriptions") I ran into:
...
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: \
backtrace when the unwind is broken at frame 5
...
What happens is the following:
- the TestUnwinder from inline-frame-cycle-unwind.py calls
gdb.UnwindInfo.add_saved_register with reg == tpidruro and value
"<unavailable>",
- pyuw_sniffer calls value->contents ().data () to access the value of the
register, which throws an UNAVAILABLE_ERROR,
- this causes the TestUnwinder unwinder to fail, after which another unwinder
succeeds and returns the correct frame, and
- the test-case fails because it's counting on the TestUnwinder to succeed and
return an incorrect frame.
Fix this by checking for !value::entirely_available as well as
valued::optimized_out in unwind_infopy_add_saved_register.
Tested on x86_64-linux and arm-linux.
PR python/31437
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31437
---
gdb/python/py-unwind.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
base-commit: a6a3b67fa9052bba81ed91a38569c11ecb95baf1
Comments
On 3/2/24 13:36, Tom de Vries wrote:
> On arm-linux, until commit bbb12eb9c84 ("gdb/arm: Remove tpidruro register
> from non-FreeBSD target descriptions") I ran into:
> ...
> FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: \
> backtrace when the unwind is broken at frame 5
> ...
>
> What happens is the following:
> - the TestUnwinder from inline-frame-cycle-unwind.py calls
> gdb.UnwindInfo.add_saved_register with reg == tpidruro and value
> "<unavailable>",
> - pyuw_sniffer calls value->contents ().data () to access the value of the
> register, which throws an UNAVAILABLE_ERROR,
> - this causes the TestUnwinder unwinder to fail, after which another unwinder
> succeeds and returns the correct frame, and
> - the test-case fails because it's counting on the TestUnwinder to succeed and
> return an incorrect frame.
>
> Fix this by checking for !value::entirely_available as well as
> valued::optimized_out in unwind_infopy_add_saved_register.
>
> Tested on x86_64-linux and arm-linux.
>
Ping.
Thanks,
- Tom
> PR python/31437
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31437
> ---
> gdb/python/py-unwind.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c
> index 56f925bc57f..1c1289f7e7d 100644
> --- a/gdb/python/py-unwind.c
> +++ b/gdb/python/py-unwind.c
> @@ -362,6 +362,18 @@ unwind_infopy_add_saved_register (PyObject *self, PyObject *args, PyObject *kw)
> return nullptr;
> }
>
> + if (value->optimized_out () || !value->entirely_available ())
> + {
> + /* If we allow this value to be registered here, pyuw_sniffer is going
> + to run into an exception when trying to access its contents.
> + Throwing an exception here just puts a burden on the user to
> + implement the same checks on the user side. We could return False
> + here and True otherwise, but again that might require changes in user
> + code. So, handle this with minimal impact for the user, while
> + improving robustness: silently ignore the register/value pair. */
> + Py_RETURN_NONE;
> + }
> +
> gdbpy_ref<> new_value = gdbpy_ref<>::new_reference (pyo_reg_value);
> bool found = false;
> for (saved_reg ® : *unwind_info->saved_regs)
>
> base-commit: a6a3b67fa9052bba81ed91a38569c11ecb95baf1
@@ -362,6 +362,18 @@ unwind_infopy_add_saved_register (PyObject *self, PyObject *args, PyObject *kw)
return nullptr;
}
+ if (value->optimized_out () || !value->entirely_available ())
+ {
+ /* If we allow this value to be registered here, pyuw_sniffer is going
+ to run into an exception when trying to access its contents.
+ Throwing an exception here just puts a burden on the user to
+ implement the same checks on the user side. We could return False
+ here and True otherwise, but again that might require changes in user
+ code. So, handle this with minimal impact for the user, while
+ improving robustness: silently ignore the register/value pair. */
+ Py_RETURN_NONE;
+ }
+
gdbpy_ref<> new_value = gdbpy_ref<>::new_reference (pyo_reg_value);
bool found = false;
for (saved_reg ® : *unwind_info->saved_regs)