GCC puts the constant variable requiring relocation into .data.rel. or
.data.rel.ro depending upon the bind type of the symbol. Extend
is_bundledable() to check these .data sections too.
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
4.18 adds -mcount-record to KBUILD_FLAGS when supported by the compiler.
This results in most of kpatch_create_mcount_sections()'s work being
already done, so we can at least skip the last part of it that updates
the first instruction in patched functions.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
According to gcc8's man pages gcc can put functions into .text.unlikely
or .text.hot subfunctions during optimization. Add ".text.hot" to the
list of bundleable functions in is_bundleable().
Signed-off-by: Artem Savkov <asavkov@redhat.com>
gcc8 can place functions to .text.unlikely and .text.hot subsections
during optimizations. Allow symbols to change subsections instead of
failing.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Add a function that would detect parent/child symbol relations. So far
it only supports .cold.* symbols as children.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Building with GCC 7.3.0 on Debian sid fails with the following error:
gcc -g -O2 -fdebug-prefix-map=/build/kpatch-0.6.0=. -fstack-protector-strong -Wformat -Werror=format-security -MMD -MP -I../kmod/patch -Iinsn -Wall -Wsign-compare -g -Werror -Wdate-time -D_FORTIFY_SOURCE=2 -c -c
create-diff-object.c: In function 'kpatch_compare_correlated_rela_section':
create-diff-object.c:316:20: error: 'toc_data1' may be used uninitialized in this function [-Werror=maybe-uninitialized]
return toc_data1 == toc_data2;
~~~~~~~~~~^~~~~~~~~~~~
create-diff-object.c:256:16: note: 'toc_data1' was declared here
unsigned long toc_data1, toc_data2;
^~~~~~~~~
cc1: all warnings being treated as errors
This is a false positive as the code only compares those two values
after initializing them. But lets keep GCC happy.
Signed-off-by: Simon Ruderich <simon@ruderich.org>
Convert magic exit status values into a common enum for clarity.
Suggested-by: Artem Savkov <asavkov@redhat.com>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Change the "FILE symbol not found in base. Stripped?" (fatal) error
message into a warning. These crop up whenever a change is made to an
assembly file.
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Finally add support for processing the ORC unwinder sections.
The ORC unwinder sections are more special than the other special
sections, so they need their own dedicated function to process them,
though the code is similar to kpatch_regenerate_special_sections().
BTW, upstream livepatch still doesn't support the ORC unwinder. That
change will be coming soon (probably Linux 4.19).
Fixes#785.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Since the codeset supports just the 64 bit variant, lets move
to __powerpc64__ and use it. I checked the ABI doc as well
and the kernel/gcc.
Signed-off-by: Balbir singh <bsingharora@gmail.com>
gcc8 introduces ".cold." optimization symbols that have arbitrary
trainling numbers in their names just like ".isra." and others.
Add ".cold." to a condition in kpatch_rename_mangled_functions()
Signed-off-by: Artem Savkov <asavkov@redhat.com>
When I made a patch to the nfsd module on a ppc64le system with a RHEL 7
based kernel, livepatch prevented the target module from loading with:
livepatch: symbol '.TOC.' not found in symbol table
References to this symbol are treated specially by the kernel module
loader, so references to it should never be converted to dynrelas.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
While building a gcc-consprop patch from integration tests gcc8 would place a
__timekeeping_inject_sleeptime.constprop.18.cold.27 symbol into
.text.unlikely.__timekeeping_inject_sleeptime.constprop.18 section. Because
section name doesn't have the '.cold.27' suffix this symbol fails
is_bundleable() check while still being bundleable and later exits early in
kpatch_rename_mangled_functions() without renaming the corresponding patched
function. All of this results in a create-diff-object errror:
ERROR: timekeeping.o: symbol changed sections: __timekeeping_inject_sleeptime.constprop.18.cold.27
/home/asavkov/dev/kpatch/kpatch-build/create-diff-object: unreconcilable difference
Fix by ignoring .cold.* name suffix in is_bundleable() for.text.unlikely
sections.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
create-diff-object doesn't really need the full kernel object file as
input. All it requires is a symbol table. Switch to using "eu-readelf -s"'s
output instead of object files. This will enable us to cover more cases
in unit tests.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Use named variables instead of cmdline argument indexes so that it is
easier to read create-diff-object.c.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Artem Savkov <asavkov@redhat.com>
ppc64le lacked kpatch_line_macro_change_only() implementation. Add one
based on x86_64 version and available unit tests.
Fixes: #843
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Update the `__LINE__` macro detection heuristics based on recent kernel
changes:
- __warn_printk(), used in the WARN macros, which put the line number in
%edx
- __might_fault(), used in the usercopy macros
- lockdep_rcu_suspicious(), used in the RCU_LOCKDEP_WARN macro
- printk(), used in the ASSERT_RTNL macro
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
With #755, we started using dynrelas for function pointers. However,
this behavior only makes sense for function pointers to existing
functions. For function pointers to *new* functions, just use a normal
rela.
The 'function-ptr-new' unit test is from the following patch:
https://github.com/dynup/kpatch/files/1927198/new-static-callback.patch.txtFixes#834.
Fixes: 495e619750 ("kpatch-build, x86: do not use the patched functions as callbacks directly")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
- convert section/symbol indexes and rela->offset to unsigned int as I
couldn't find any way for them to become negative.
- cast a number of rela->addend comparisons to int (assuming an 64bit
system this should be enough)
- a number of simple for-loop counter conversions to the type it
compares against
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Because of signedness difference kpatch_check_relocations() would trigger
an error on any negative addend.
Fix by casting Elf_Data->d_size from size_t to int.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Check that none of the relocations are out-of-range of their
corresponding sections before writing the output elf.
Fixes: #618
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Heavy lifting of reading .toc rela entries for rela symbols
referring to .toc + offset, can be simplified using toc_rela() in
rela_equal() and remove the #ifdery guarding PowerPC code.
This patch also trims the commentary related to PowerPC.
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
On ppc64le, the static local variable correlation doesn't take into
account the .toc rela indirection for data references, meaning that it's
basically broken in many cases.
Fix it by making the code .toc-aware.
Fixes#793.
Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Upstream 4.15 kernels provide support for pre and post (un)patch
callbacks, inspired by the kpatch load hooks. Add support for them
in the livepatch-patch-hook.
At the same time, convert the kpatch hooks to use the same API.
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
kpatch_include_symbol() is confusing. Refactor it:
- Remove the "inclusion tree" debug messages. I never use them, and
they just help make the code more confusing and the debug output more
cluttered.
- Split it up into two functions: kpatch_include_symbol() and
kpatch_include_section(), so that kpatch_include_section() can be used
elsewhere.
- Call kpatch_include_section() from kpatch_include_standard_elements().
This covertly fixes#702, by also including the .rela.rodata section.
- Add a bunch of comments to clarify some of the trickier points.
Fixes#702.
Fixes#807.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
It was observed by Evgenii Shatokhin in PR#755, that when the RCU
callback was called on the patched function, from unloaded livepatch
module triggered a kernel crash.
This patch implements the approach on PowerPC outlined in PR#755.
With -mcmodel=large, like any other data, function pointers are also
loaded relative to the current TOC base and are populated as
relocation entries in .toc section. Every function passing a function
pointer as the argument need to load the function address through
.toc section + offset. Convert such .toc + offset relocation into
a dynamic rela, which resolves to original function address, during
module load.
Also move the comment related to nested function check, into
may_need_dynrela().
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Evgenii Shatokhin <eshatokhin@virtuozzo.com>
Cc: Joe Lawrence <jdl1291@gmail.com>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
A kernel crash happened in __do_softirq() in very rare cases when the
binary patch created from mainline commit be82485fbcbb
("netlink: fix an use-after-free issue for nlk groups") was unloaded.
Investigation has shown that the kernel tried to execute an RCU
callback, deferred_put_nlk_sk(), defined in the patch module after the
module had been unloaded.
The callback was set by the patched variant of netlink_release() and
the address of the patched deferred_put_nlk_sk() was used, rather than
the address of the original function.
Similar problems occur with workqueue functions as well.
As suggested in
https://github.com/dynup/kpatch/pull/755#issuecomment-344135224,
create-diff-object was modified so that the addresses of the original
functions were used in such situations, at least for x86 systems. A
similar fix for PowerPC was added as well.
Changes in v4:
* '#ifdef __x86_64__' was removed. It is not actually needed right now
because the constants for relocation types are different on different
architectures.
Changes in v3:
* Minor refactoring and a comment explaining what this all is about.
Quite lengthy, but the dynrela-related code is really far from obvious.
Changes in v2:
* Handle the nested functions the same way as before, because they are
unlikely to be used as asynchronous callbacks. Example: cmp() in
bch_cache_show() from drivers/md/bcache/sysfs.c in the kernel 4.4.
As the nested functions are local to the functions they are defined in,
the compiler names them in a similar way to static locals: <name>.<number>.
Currently, we filter out all functions with '.' in their names. If there
are any asynchronous callbacks in the kernel that have a dot in their
names too, they could be handled in the future patches. It is unclear
though, if the callbacks with such names can appear in the kernel.
Signed-off-by: Evgenii Shatokhin <eshatokhin@virtuozzo.com>
With kernel commit b1fca27d384 ("kernel debug: support resetting
WARN*_ONCE") the *_ONCE warnings are placed .data.once section.
Including .data.once section is valid, so add an check in
kpatch_verify_patchability() while checking for included invalid
sections.
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Symbols with R_PPC64_REL24 relocation type are functions and it's
currently assumed that all functions are replaced with their respective
section symbols.
There are function whose reference are not straight forward section
symbol but section + offset. These function replacement should be
handled more like bundled sections. Remove the check, which imposes
the inital assumption.
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
.toc section entries are mostly place holder for relocation entries,
specified in .rela.toc section. Sometimes, .toc section may have
constants as entries. These constants are not reference to any symbols,
but plain instructions mostly due to some arthimetics in the functions
referring them.
They are referred by the functions like normal .toc entries, these
entries can not be resolved to any symbols. This patch creates a list
of constants if available for .toc sections and compares them in
rela_equal() to ensure their is no mismatch in the generated constants
for original and patched .o files.
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
GCC 7.2.1 complains about the usage of the PPC64_LOCAL_ENTRY_OFFSET
macro:
create-diff-object.c: In function ‘is_gcc6_localentry_bundled_sym’:
create-diff-object.c:119:83: error: ‘<<’ in boolean context, did you mean ‘<’ ? [-Werror=int-in-bool-context]
(((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
create-diff-object.c:140:10: note: in expansion of macro ‘PPC64_LOCAL_ENTRY_OFFSET’
return (PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other) &&
^~~~~~~~~~~~~~~~~~~~~~~~
Fix it by explicitly treating the macro as an integer instead of a bool.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Found in the scope of https://github.com/dynup/kpatch/pull/755 but not
related to the main problem discussed there.
kpatch_create_patches_sections() and kpatch_create_intermediate_sections()
used 'hint' in error messages.
However, the string 'hint' refers to is owned by 'kelf_base' and is
freed before kpatch_create_*_sections() are called. As a result, if
these functions try to output errors and print 'hint',
create-diff-object will crash.
As suggested in the mentioned PR, 'hint' is actually no longer needed at
that stage, so I have removed it from kpatch_create_*_sections().
When creating .kpatch.relocations, there's no reason to convert the
relocation destinations to symbols. In fact, it's actively harmful
because it makes it harder for create-klp-module to deal with the GCC 6+
8-byte localentry gap.
This also fixes a regression which was introduced in 5888f316e6, which
broke ppc64le relocations.
Fixes#754.
Fixes: 5888f316e6 ("create-klp-module: support unbundled symbols")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
kpatch_relocation's 'dest' addend and 'offset' fields are redundant. In
fact, the 'offset' field isn't always accurate because it doesn't have a
relocation, so its value doesn't adjust when multiple .o files are
combined. Just use the 'dest' addend instead.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
