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When building a patch to a single-file kernel module with
CONFIG_MODULE_SRCVERSION_ALL enabled, the klp-build module link fails in
modpost:
Diffing objects
drivers/md/raid0.o: changed function: raid0_run
Building patch module: livepatch-0001-patch-raid0_run.ko
drivers/md/raid0.c: No such file or directory
...
The problem here is that klp-build copied drivers/md/.raid0.o.cmd to the
module build directory, but it didn't also copy over the input source
file listed in the .cmd file:
source_drivers/md/raid0.o := drivers/md/raid0.c
So modpost dies due to the missing .c file which is needed for
calculating checksums for CONFIG_MODULE_SRCVERSION_ALL.
Instead of copying the original .cmd file, just create an empty one.
Modpost only requires that it exists. The original object's build
dependencies are irrelevant for the frankenobjects used by klp-build.
Fixes: 24ebfcd65a87 ("livepatch/klp-build: Introduce klp-build script for generating livepatch modules")
Reported-by: Song Liu <song@kernel.org>
Tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/c41b6629e02775e4c1015259aa36065b3fe2f0f3.1769471792.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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With CONFIG_KLP_BUILD enabled, checksums are only needed during a
klp-build run. There's no need to enable them for normal kernel builds.
This also has the benefit of softening the xxhash dependency.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Link: https://patch.msgid.link/edbb1ca215e4926e02edb493b68b9d6d063e902f.1762990139.git.jpoimboe@kernel.org
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Add a --show-first-changed option to identify where changed functions
begin to diverge:
- Parse 'objtool klp diff' output to find changed functions.
- Run objtool again on each object with --debug-checksum=<funcs>.
- Diff the per-instruction checksum debug output to locate the first
differing instruction.
This can be useful for quickly determining where and why a function
changed.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a --debug option which gets passed to "objtool klp diff" to enable
debug output related to cloning decisions.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a klp-build script which automates the generation of a livepatch
module from a source .patch file by performing the following steps:
- Builds an original kernel with -function-sections and
-fdata-sections, plus objtool function checksumming.
- Applies the .patch file and rebuilds the kernel using the same
options.
- Runs 'objtool klp diff' to detect changed functions and generate
intermediate binary diff objects.
- Builds a kernel module which links the diff objects with some
livepatch module init code (scripts/livepatch/init.c).
- Finalizes the livepatch module (aka work around linker wreckage)
using 'objtool klp post-link'.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a module initialization stub which can be linked with binary diff
objects to produce a livepatch module.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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noise
The __LINE__ macro creates challenges for binary diffing. When a .patch
file adds or removes lines, it shifts the line numbers for all code
below it.
This can cause the code generation of functions using __LINE__ to change
due to the line number constant being embedded in a MOV instruction,
despite there being no semantic difference.
Avoid such false positives by adding a fix-patch-lines script which can
be used to insert a #line directive in each patch hunk affecting the
line numbering. This script will be used by klp-build, which will be
introduced in a subsequent patch.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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