Add support for patching a function multiple times. If multiple patches
affect a function, the function in the most recently enabled patch
"wins". This enables a cumulative patch upgrade path, where each patch
is a superset of previous patches.
This requires restructuring the data a little bit. With the current
design, where each klp_func struct has its own ftrace_ops, we'd have to
unregister the old ops and then register the new ops, because
FTRACE_OPS_FL_IPMODIFY prevents us from having two ops registered for
the same function at the same time. That would leave a regression
window where the function isn't patched at all (not good for a patch
upgrade path).
This patch replaces the per-klp_func ftrace_ops with a global klp_ops
list, with one ftrace_ops per original function. A single ftrace_ops is
shared between all klp_funcs which have the same old_addr. This allows
the switch between function versions to happen instantaneously by
updating the klp_ops struct's func_stack list. The winner is the
klp_func at the top of the func_stack (front of the list).
[ jkosina@suse.cz: turn WARN_ON() into WARN_ON_ONCE() in ftrace handler to
avoid storm in pathological cases ]
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Only allow the topmost patch on the stack to be enabled or disabled, so
that patches can't be removed or added in an arbitrary order.
Suggested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Change ARCH_HAVE_LIVE_PATCHING to HAVE_LIVE_PATCHING in Kconfigs. HAVE_
bools are prevalent there and we should go with the flow.
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
When applying multiple patches to a module, if the module is loaded
after the patches are loaded, the patches are applied in reverse order:
$ insmod patch1.ko
[ 43.172992] livepatch: enabling patch 'patch1'
$ insmod patch2.ko
[ 46.571563] livepatch: enabling patch 'patch2'
$ modprobe nfsd
[ 52.888922] livepatch: applying patch 'patch2' to loading module 'nfsd'
[ 52.899847] livepatch: applying patch 'patch1' to loading module 'nfsd'
Fix the loading order by storing the klp_patches list in queue order.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
We are aborting a build in case when gcc doesn't support fentry on x86_64
(regs->ip modification can't really reliably work with mcount).
This however breaks allmodconfig for people with older gccs that don't
support -mfentry.
Turn the build-time failure into runtime failure, resulting in the whole
infrastructure not being initialized if CC_USING_FENTRY is unset.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Use the FTRACE_OPS_FL_IPMODIFY flag to prevent conflicts with other
ftrace users who also modify regs->ip.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
The execution flow redirection related implemention in the livepatch
ftrace handler is depended on the specific architecture. This patch
introduces klp_arch_set_pc(like kgdb_arch_set_pc) interface to change
the pt_regs.
Signed-off-by: Li Bin <huawei.libin@huawei.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit introduces code for the live patching core. It implements
an ftrace-based mechanism and kernel interface for doing live patching
of kernel and kernel module functions.
It represents the greatest common functionality set between kpatch and
kgraft and can accept patches built using either method.
This first version does not implement any consistency mechanism that
ensures that old and new code do not run together. In practice, ~90% of
CVEs are safe to apply in this way, since they simply add a conditional
check. However, any function change that can not execute safely with
the old version of the function can _not_ be safely applied in this
version.
[ jkosina@suse.cz: due to the number of contributions that got folded into
this original patch from Seth Jennings, add SUSE's copyright as well, as
discussed via e-mail ]
Signed-off-by: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
