bpo-32962: Fix test_gdb failure in debug build with -mcet -fcf-protection -O0 · Pull Request #6754 · python/cpython (original) (raw)
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This pull request solves problem with reading stack of the interpreter from gdb when new protection flags are used.
The new flags also cause some noise, which is now ignored, on stderr.
https://bugs.python.org/issue32962
Reminder for reviewers: test_gdb is not run on Travis CI. Tests must be run manually before merging such change.
Also in order to test the change, gcc >= 8 is required.
bpo-32962: test_gdb fails in debug build with bpo-32962: Fix test_gdb failure in debug build with -mcet -fcf-protection -O0-mcet -fcf-protection -O0
When Python is built with the intel control-flow protection flags, -mcet -fcf-protection, gdb is not able to read the stack without actually jumping inside the function. This means an extra 'next' command is required to make the $pc (program counter) enter the function and make the stack of the function exposed to gdb.
| @@ -202,6 +202,8 @@ def get_stack_trace(self, source=None, script=None, |
|---|
| 'BFD: ', |
| # ignore all warnings |
| 'warning: ', |
| # See #32962 |
| 'Python Exception', |
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Hum, this is not a good idea to ignore bugs :-( Please revert this change.
My #7693 should fix this bug.
| @@ -162,7 +162,7 @@ def get_stack_trace(self, source=None, script=None, |
|---|
| commands += ['set print entry-values no'] |
| if cmds_after_breakpoint: |
| commands += cmds_after_breakpoint |
| commands += ['next'] + cmds_after_breakpoint |
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Please add a comment explaining why next is needed. Something like:
# bpo-32962: When Python is compiled with -mcet -fcf-protection,
# arguments are unusable before running the first instruction
# of the function entry point.
| @@ -849,7 +851,7 @@ def __init__(self): |
|---|
| ''') |
| # Verify with "py-bt": |
| gdb_output = self.get_stack_trace(cmd, |
| cmds_after_breakpoint=['break wrapper_call', 'continue', 'py-bt']) |
| cmds_after_breakpoint=['break wrapper_call', 'continue', 'next', 'py-bt']) |
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Ditto: please add a comment.
Marcel Plch added 2 commits
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LGTM, just two minor remarks on comments.
| @@ -161,8 +161,11 @@ def get_stack_trace(self, source=None, script=None, |
|---|
| if (gdb_major_version, gdb_minor_version) >= (7, 4): |
| commands += ['set print entry-values no'] |
| # bpo-32962: When Python is compiled with -mcet -fcf-protection, |
| # arguments are unusable before running the first instruction |
| # of the function entry point. Next makes the required first step. |
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Would you mind to replace Next with >The 'next' command< to make it more explicit?
Move also the comment inside the if block.
| @@ -847,9 +850,12 @@ def __init__(self): |
|---|
| id("first break point") |
| l = MyList() |
| ''') |
| # bpo-32962: same case as in get_stack_trace(): |
| # we need one extra step in order to read arguments |
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Replace "we need one extra step" with "we need 'next' extra command".
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LGTM.
@vstinner: Please replace # with GH- in the commit message next time. Thanks!
vstinner added a commit that referenced this pull request
python-gdb now catchs ValueError on read_var(): when Python has no debug symbols for example.
(cherry picked from commit 019d33b)
python-gdb now catchs UnicodeDecodeError exceptions when calling string().
(cherry picked from commit d22fc0b)
When Python is built with the intel control-flow protection flags, -mcet -fcf-protection, gdb is not able to read the stack without actually jumping inside the function. This means an extra 'next' command is required to make the $pc (program counter) enter the function and make the stack of the function exposed to gdb.
(cherry picked from commit 9b7c74c)
vstinner added a commit that referenced this pull request
… (GH-7711)
python-gdb now catchs ValueError on read_var(): when Python has no debug symbols for example.
(cherry picked from commit 019d33b)
python-gdb now catchs UnicodeDecodeError exceptions when calling string().
(cherry picked from commit d22fc0b)
When Python is built with the intel control-flow protection flags, -mcet -fcf-protection, gdb is not able to read the stack without actually jumping inside the function. This means an extra 'next' command is required to make the $pc (program counter) enter the function and make the stack of the function exposed to gdb.
(cherry picked from commit 9b7c74c)
(cherry picked from commit ca4cb84)
vstinner added a commit that referenced this pull request
vstinner added a commit that referenced this pull request
vstinner added a commit that referenced this pull request