On 12/14/2018 11:56 AM, Nicholas Mc Guire wrote: > Sparse reported warnings about non-static symbols. For the variables a > simple static attribute is fine - for those symbols referenced by > livepatch via klp_func the symbol-names must be unmodified in the > relocation table - to resolve this the __noclone attribute (as ^^^^^^^^^^ nit: symbol table > suggested by Joe Lawrence <joe.lawrence@xxxxxxxxxx>) is used > for the statically declared functions. > > Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx> > Link: https://lkml.org/lkml/2018/12/13/827 > --- > > sparse reported the following warnings: > > CHECK samples/livepatch/livepatch-shadow-fix1.c > samples/livepatch/livepatch-shadow-fix1.c:74:14: warning: symbol > 'livepatch_fix1_dummy alloc' was not declared. Should it be static? > samples/livepatch/livepatch-shadow-fix1.c:116:6: warning: symbol > 'livepatch_fix1_dummy free' was not declared. Should it be static? > > CHECK samples/livepatch/livepatch-shadow-mod.c > samples/livepatch/livepatch-shadow-mod.c:99:1: warning: symbol > 'dummy_list' was not declared. Should it be static? > samples/livepatch/livepatch-shadow-mod.c:100:1: warning: symbol > 'dummy_list_mutex' was not declared. Should it be static? > samples/livepatch/livepatch-shadow-mod.c:107:23: warning: symbol > 'dummy_alloc' was not declared. Should it be static? > samples/livepatch/livepatch-shadow-mod.c:132:15: warning: symbol > 'dummy_free' was not declared. Should it be static? > samples/livepatch/livepatch-shadow-mod.c:140:15: warning: symbol > 'dummy_check' was not declared. Should it be static? > > Patch was compile tested with: x86_64_defconfig + FTRACE=y > FUNCTION_TRACER=y, EXPERT=y, LATENCYTOP=y, SAMPLES=y, > SAMPLE_LIVEPATCH=y > > Patch was runtested on an Intel i3 with: > insmod samples/livepatch/livepatch-shadow-mod.ko > insmod samples/livepatch/livepatch-shadow-fix1.ko > insmod samples/livepatch/livepatch-shadow-fix2.ko > echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix2/enabled > echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix1/enabled > rmmod livepatch-shadow-fix2 > rmmod livepatch-shadow-fix1 > rmmod livepatch-shadow-mod > and dmesg output checked. > > Patch is against 4.20-rc6 (localversion-next is next-20181214) Great testing notes, thanks for including these! > samples/livepatch/livepatch-shadow-fix1.c | 4 ++-- > samples/livepatch/livepatch-shadow-mod.c | 16 +++++++++++----- > 2 files changed, 13 insertions(+), 7 deletions(-) Almost. We should only need to annotate with __noclone for those function definitions which the samples will be patching. As the commit message says, these correlate to klp_func.old_name functions found in klp_object.name objects (.ko modules or NULL for vmlinux). For the functions defined in samples/livepatch/*.c those would be: livepatch-callbacks-busymod.c :: busymod_work_func() livepatch-shadow-mod.c :: dummy_alloc() livepatch-shadow-mod.c :: dummy_free() livepatch-shadow-mod.c :: dummy_check() So even though livepatch-shadow-fix2 further refines livepatch-shadow-fix1, the livepatch core is going to redirect the original dummy_*() calls defined by livepatch-shadow-mod.c in both fix1 and fix2 cases. Ie, the fixes modules aren't patched, only the original. > > diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c > index 49b1355..eaab10f 100644 > --- a/samples/livepatch/livepatch-shadow-fix1.c > +++ b/samples/livepatch/livepatch-shadow-fix1.c > @@ -71,7 +71,7 @@ static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data) > return 0; > } > > -struct dummy *livepatch_fix1_dummy_alloc(void) > +static __noclone struct dummy *livepatch_fix1_dummy_alloc(void) > { > struct dummy *d; > void *leak; > @@ -108,7 +108,7 @@ static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data) > __func__, d, *shadow_leak); > } > > -void livepatch_fix1_dummy_free(struct dummy *d) > +static __noclone void livepatch_fix1_dummy_free(struct dummy *d) > { > void **shadow_leak; > > diff --git a/samples/livepatch/livepatch-shadow-mod.c b/samples/livepatch/livepatch-shadow-mod.c > index 4c54b25..0a72bc2 100644 > --- a/samples/livepatch/livepatch-shadow-mod.c > +++ b/samples/livepatch/livepatch-shadow-mod.c > @@ -30,6 +30,11 @@ > * memory leak, please load these modules at your own risk -- some > * amount of memory may leaked before the bug is patched. > * > + * NOTE - the __noclone attribute to those functions that are to be > + * shared with other modules while being declared static. As livepatch > + * needs the unmodified symbol names and the usual "static" would > + * invoke gccs cloning mechanism that renames the functions this > + * needs to be suppressed with the additional __noclone attribute. I like the idea of providing the sample code reader this information, but since the compiler might also optimize livepatch-callbacks-busymod.c :: busymod_work_func(), it too should be annotated __noclone. Would that file deserve a similar comment? I don't have a strong opinion, but would throw my vote at leaving this in the commit message only. BTW, Petr/Miroslav/Josh, should we be annotating the selftests in similar fashion? > [ ... snip ... ] Thanks for working on this, -- Joe
