For ftrace to be able to trace a patched function, it requires that the
__mcount_loc section contains a pointer to the function, and that the
first instruction of the function is "callq __fentry__".
Normally that work is done by the recordmcount script, but it ignores
functions that aren't in a few standard sections (.text and a few
others).
This commit enables the ability to create user-defined hooks as part of
the normal code patch that can do preparatory work for the application
of the patch. This work could include, but is not limited to, changing
data structure semantics.
The user may define a new function as part of the patch and mark it as a
load-time or unload-time hook with the kpatch_load_hook() and
kpatch_unload_hook() macros. These macros are in an include file that
gets copied into the source tree at include/linux/kpatch-hooks.h at
patch build time. The signature for both hooks is "int kpatch_unload_hook(void)".
For now, the return code is ignored. The hooks may not fail. They also
run in stop_machine() context and may not sleep. These hooks, more or
less, must follow all the rules of interrupt context code.
The printks in the integration tests aren't very useful and annoyingly
fill up the dmesg buffer. Remove them by making them contingent on
unlikely conditions.
The original logic in the inclusion tree code worked under the
assumption that it was the only code path marking symbols for inclusion.
Therefore, if the symbol had been marked as included, it could be safely
assumed that we also already called kpatch_include_symbol() on it. With
the special section handling marking symbols as included, however, this
assumption is not valid.
We should call kpatch_include_symbol() regardless of whether or not the
symbol has already been marked as included or not in order to possible
include the symbol's entire bundle.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
The integration test suite was intermittently giving the following
error:
[192685.907072] kpatch: write to 0xffffffffa082bffe failed for symbol call_netdevice_notifiers_info
The error was caused by a write across a page boundary without first
making the second page read/write.
With the inclusion of the debug sections, the debug output is so verbose
that it becomes less useful.
This commit reduces the verbosity by skipping rela listings of debug
sections.
It includes a new helper function, is_debug_section(), to consolidate
the logic for detecting debug sections.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
This is useful if ~/.kpatch is a symlink or a tmpfs mount.
- move SRCDIR/OBJDIR/OBJDIR2 initialization to the top
- create new VERSIONFILE variable
- create new clean_cache function which doesn't remove ~/.kpatch
Fixes#261.
Right now, if there is a failure in patch_make_dynrelas_list(),
patch_free_objects() is called twice; once in the error section of
patch_make_dynrelas_list() and again in the err_objects section of
patch_init().
This fixes this and cleans up the error handling a bit.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
In my experience this is a much more useful implementation of the
"--sourcedir" option:
- use the source tree in-place rather than first copying it to
~/.kpatch/src. In my case this avoids a 5GB copy, including the
entire .git subdirectory, and allows ccache to be reused.
- find the vmlinux and .config files in the sourcedir
- autodetect the ARCHVERSION
Add -d option to create-diff-object when DEBUG is set. That way for
weird kpatch-build issues we can just tell people to use the -d flag and
then provide the build log.
- replace the old low-level video with the new high-level one, and place
it with screenshot prominently at the top
- increase default ccache size
- remove obsolete NOTEs
- add blurb about patching modules and -t
- "trampoline" -> "handler"
- more details about ftrace, perf, tracepoints compatibility
- add recommended practice re: single cumulative module vs multiple
independent modules
