On RHEL 7 I see the following error when trying to patch meminfo.o:
cp: cannot stat ‘/home/user/.kpatch/obj/fs/proc/.tmp_meminfo.o’: No such file or directory
It turns out that on RHEL 7, a given object foo.o is compiled as
.tmp_foo.o before then being linked as foo.o. I have no idea why. The
fix is to record .tmp_foo.o as foo.o in the changed_objs file.
The purpose of this test script is to determine if create-diff-object
can properly recognize object file equivalence when passed the same file
for both the original and patched objects. This verifies that
create-diff-object is correctly parsing, correlating, and comparing the
different elements of the object file. In practice, a situation similar
to the test case occurs when a commonly included header file changes,
causing Make to rebuild many objects that have no functional change.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
GROUP section are rare and are a mechanism in the ELF to indicated that
certain groups of section must be included or excluded (stripped)
together.
It is valid to have more than one of these section with the same
".group" name. This currently messes up the section correlation code
with correlates based solely on name.
This commit adds additional correlation criteria for GROUP sections;
namely, the section content must be the same. Changing of groups
sections (i.e. reindexing of the section indexes the GROUP section
includes in their section data) is not supported and will result in a
"new/changed section not included" error.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
The FILES variable can contain unchanged objects, so don't use it to
determine which objects to link. Instead, just use all the objects that
were placed in the output directory by create-diff-object.
There are situations in which an object may be rebuilt but have no
functional changes, such as a change to an included header file.
This commit changes kpatch-build to tolerate individual unchanged
objects so long as there is, in the end, at least one changed object.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
Right now, we do three build passes: one to build the original tree
(full) build, one to build the patch tree (diff build), then one to
rebuild original objects that where changed by the patch (diff build).
This is going to be a problem when we try to support (near) full tree
rebuilds due to changes in commonly included header files.
This commit changes the build process to intercept calls to gcc by make
using the CROSS_COMPILE environment variable and, during the patched
build phase, copies the original object for any object that is about to
rebuilt due to a change.
This reduces the number of build passes to the minimum possible (two).
Signed-off-by: Seth Jennings <sjenning@redhat.com>
Fixes the following error:
kpatch_correlate_static_local_variables: 850: found another static local variable matching __func__.49968 in patched .rela__verbose
Detect .rodata.* bundled sections so that .rodata.__func__.* relocation
references can be converted to refer to their corresponding object
symbols.
Fixes the following error:
kpatch_correlate_static_local_variables: 830: static local variable __func__.49968 not used
The __verbose section stores several static local structs named
"descriptor". These structs contain information related to dynamic
debugging printks and are specific to the patched object, so they
shouldn't be correlated with their base object counterparts.
Fixes the following error:
kpatch_correlate_static_local_variables: 830: static local variable descriptor.49967 not used
Use this instead of calling printk to avoid unwanted compiler
optimizations which cause kpatch-build errors.
The printk function is annotated with the __cold attribute, which tells
gcc that the function is unlikely to be called. A side effect of this
is that code paths containing calls to printk might also be marked cold,
leading to other functions called in those code paths getting moved into
.text.unlikely or being uninlined.
This macro places printk in its own code path so as not to make the
surrounding code path cold.
I have a related integration test to add, but right now it's broken
because we don't yet properly support the __verbose special section.
That'll be another PR.
Fixes#296.
On RHEL I'm seeing issues with putting the core module in the "extra"
path. On the next depmod run, it gets added to modules.dep, and on a
subsequent kpatch install I see the following errors:
/usr/lib/dracut/modules.d/50drm/module-setup.sh: line 26: /lib/modules/3.10.0-123.4.4.el7.x86_64//weak-updates/kpatch/kpatch.ko: No such file or directory
/usr/lib/dracut/modules.d/90kernel-modules/module-setup.sh: line 14: /lib/modules/3.10.0-123.4.4.el7.x86_64//weak-updates/kpatch/kpatch.ko: No such file or directory
modinfo: ERROR: Module /lib/modules/3.10.0-123.4.4.el7.x86_64/weak-updates/kpatch/kpatch.ko not found.
Until the core module gets merged into Linux, I think we can put it in
/usr/lib/kpatch, which is also where the patch modules are going to be
delivered in the RHEL RPM.
Making sure the other options still work with the kpatch utility for
now, so as to keep backwards compatibility between a newer kpatch
utility and older core modules. We can break this compatibility for
kpatch 0.2.0.
Right now, the test patch unnecessarily includes hrtimer_nanosleep()
because the call to do_nanosleep() generates a rela the references the
unbundled .sched.text section. This section symbol is not currently
replaced by kpatch_replace_sections_syms() as it only replaces bundled
sections symbols.
This commit adds logic to kpatch_replace_sections_syms() to replace
unbundled section symbols as well by scanning the symbol table for
symbols that start at the rela entry's offset within the matching
section.
This allows for properly rela section correlation when the functions
have moved from an unbundled section to a bundled section.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
This macro is for ignoring sections that may change as a side effect of
another change or might be a non-bundlable section; that is one that
does not honor -ffunction-section and create a one-to-one relation from
function symbol to section.
Signed-off-by: Seth Jennings <sjenning@redhat.com>
