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* [binutils-gdb] [gdb/python] Make gdb.UnwindInfo.add_saved_register more robust
@ 2024-05-08 12:12 Tom de Vries
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From: Tom de Vries @ 2024-05-08 12:12 UTC (permalink / raw)
To: gdb-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2236c5e384de20b0dd6b2fbc964a7269027cb2d9
commit 2236c5e384de20b0dd6b2fbc964a7269027cb2d9
Author: Tom de Vries <tdevries@suse.de>
Date: Wed May 8 14:13:11 2024 +0200
[gdb/python] Make gdb.UnwindInfo.add_saved_register more robust
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.
Approved-By: Andrew Burgess <aburgess@redhat.com>
PR python/31437
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31437
Diff:
---
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 a86ccd2c94e..18125e56a46 100644
--- a/gdb/python/py-unwind.c
+++ b/gdb/python/py-unwind.c
@@ -361,6 +361,18 @@ 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)
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