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author | Peter Zijlstra <peterz@infradead.org> | 2020-04-29 10:24:45 -0500 |
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committer | Jiri Kosina <jkosina@suse.cz> | 2020-05-08 00:12:42 +0200 |
commit | 1d05334d2899bd3ecdf01beb53f0a70884a7f471 (patch) | |
tree | b6e55679f1261a26b7c590c1f2542b1667cd90d0 /arch/x86/kernel/Makefile | |
parent | 7c8e2bdd5f0d990e2398ee3deafc626dd469fc2d (diff) | |
download | linux-stable-1d05334d2899bd3ecdf01beb53f0a70884a7f471.tar.gz linux-stable-1d05334d2899bd3ecdf01beb53f0a70884a7f471.tar.bz2 linux-stable-1d05334d2899bd3ecdf01beb53f0a70884a7f471.zip |
livepatch: Remove .klp.arch
After the previous patch, vmlinux-specific KLP relocations are now
applied early during KLP module load. This means that .klp.arch
sections are no longer needed for *vmlinux-specific* KLP relocations.
One might think they're still needed for *module-specific* KLP
relocations. If a to-be-patched module is loaded *after* its
corresponding KLP module is loaded, any corresponding KLP relocations
will be delayed until the to-be-patched module is loaded. If any
special sections (.parainstructions, for example) rely on those
relocations, their initializations (apply_paravirt) need to be done
afterwards. Thus the apparent need for arch_klp_init_object_loaded()
and its corresponding .klp.arch sections -- it allows some of the
special section initializations to be done at a later time.
But... if you look closer, that dependency between the special sections
and the module-specific KLP relocations doesn't actually exist in
reality. Looking at the contents of the .altinstructions and
.parainstructions sections, there's not a realistic scenario in which a
KLP module's .altinstructions or .parainstructions section needs to
access a symbol in a to-be-patched module. It might need to access a
local symbol or even a vmlinux symbol; but not another module's symbol.
When a special section needs to reference a local or vmlinux symbol, a
normal rela can be used instead of a KLP rela.
Since the special section initializations don't actually have any real
dependency on module-specific KLP relocations, .klp.arch and
arch_klp_init_object_loaded() no longer have a reason to exist. So
remove them.
As Peter said much more succinctly:
So the reason for .klp.arch was that .klp.rela.* stuff would overwrite
paravirt instructions. If that happens you're doing it wrong. Those
RELAs are core kernel, not module, and thus should've happened in
.rela.* sections at patch-module loading time.
Reverting this removes the two apply_{paravirt,alternatives}() calls
from the late patching path, and means we don't have to worry about
them when removing module_disable_ro().
[ jpoimboe: Rewrote patch description. Tweaked klp_init_object_loaded()
error path. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'arch/x86/kernel/Makefile')
-rw-r--r-- | arch/x86/kernel/Makefile | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index ba89cabe5fcf..bae9f9033734 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -90,7 +90,6 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o obj-y += apic/ obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o -obj-$(CONFIG_LIVEPATCH) += livepatch.o obj-$(CONFIG_FUNCTION_TRACER) += ftrace_$(BITS).o obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o |