Messages in this thread | | | Date | Wed, 16 Feb 2022 15:32:41 -0500 | From | Joe Lawrence <> | Subject | Re: [PATCH v10 02/15] livepatch: avoid position-based search if `-z unique-symbol` is available |
| |
On Mon, Feb 14, 2022 at 10:10:00AM -0800, Josh Poimboeuf wrote: > On Mon, Feb 14, 2022 at 01:24:33PM +0100, Alexander Lobakin wrote: > > > One idea I mentioned before, it may be worth exploring changing the "F" > > > in FGKASLR to "File" instead of "Function". In other words, only > > > shuffle at an object-file granularity. Then, even with duplicates, the > > > <file+function> symbol pair doesn't change in the symbol table. And as > > > a bonus, it should help FGKASLR i-cache performance, significantly. > > > > Yeah, I keep that in mind. However, this wouldn't solve the > > duplicate static function names problem, right? > > Let's say you have a static function f() in file1 and f() in file2, > > then the layout each boot can be > > > > .text.file1 or .text.file2 > > f() f() > > .text.file2 .text.file1 > > f() f() > > > > and position-based search won't work anyway, right? > > Right, so we'd have to abandon position-based search in favor of > file+func based search. > > It's not perfect because there are still a few file+func duplicates. > But it might be good enough. We would presumably just refuse to patch a > duplicate. Or we could remove them (and enforce their continued removal > with tooling-based warnings). >
You're talking about duplicate file+func combinations as stored in the symbol table?
From a recent rhel-9 development kernel:
$ readelf --wide --symbols vmlinux | \ awk '$4=="FILE" { f=$NF } $4=="OBJECT" || $4=="FUNC" { print $4 " " f "::" $NF }' | \ sort | uniq -c | sort -n | awk '$1 != 1'
2 FUNC bus.c::new_id_store 2 FUNC core.c::native_read_msr 2 FUNC core.c::type_show 2 FUNC diag.c::sk_diag_fill.constprop.0 2 FUNC hid-core.c::hid_exit 2 FUNC hid-core.c::hid_init 2 FUNC inode.c::remove_one 2 FUNC iommu.c::__list_del_entry 2 FUNC msr.c::msr_init 2 FUNC msr.c::msr_read 2 FUNC proc.c::c_next 2 FUNC proc.c::c_start 2 FUNC proc.c::c_stop 2 FUNC raw.c::copy_overflow 2 FUNC raw.c::dst_output 2 FUNC route.c::dst_discard 2 FUNC sysfs.c::name_show 2 FUNC udp.c::copy_overflow 2 FUNC udp.c::udp_lib_close 2 FUNC udp.c::udp_lib_hash 2 FUNC udp.c::udplite_getfrag 2 FUNC udplite.c::udp_lib_close 2 FUNC udplite.c::udp_lib_hash 2 FUNC udplite.c::udplite_sk_init 2 OBJECT acpi.c::__func__.0 2 OBJECT amd.c::__already_done.10 2 OBJECT amd.c::__func__.4 2 OBJECT amd.c::__func__.5 2 OBJECT bus.c::driver_attr_new_id 2 OBJECT bus.c::__func__.1 2 OBJECT bus.c::__func__.2 2 OBJECT bus.c::__func__.3 2 OBJECT bus.c::__func__.4 2 OBJECT bus.c::__func__.5 2 OBJECT bus.c::__func__.6 2 OBJECT bus.c::__func__.7 2 OBJECT bus.c::__func__.8 2 OBJECT bus.c::__func__.9 2 OBJECT cgroup.c::__func__.0 2 OBJECT class.c::__func__.0 2 OBJECT class.c::__func__.1 2 OBJECT class.c::__func__.3 2 OBJECT class.c::__func__.5 2 OBJECT class.c::__key.0 2 OBJECT class.c::__key.1 2 OBJECT class.c::__key.4 2 OBJECT core.c::__already_done.18 2 OBJECT core.c::__already_done.19 2 OBJECT core.c::__already_done.3 2 OBJECT core.c::dev_attr_size 2 OBJECT core.c::dev_attr_start 2 OBJECT core.c::dev_attr_type 2 OBJECT core.c::empty_attrs 2 OBJECT core.c::__func__.10 2 OBJECT core.c::__func__.14 2 OBJECT core.c::__func__.7 2 OBJECT core.c::__func__.9 2 OBJECT core.c::__key.0 2 OBJECT core.c::__key.2 2 OBJECT core.c::__key.3 2 OBJECT dev.c::__func__.0 2 OBJECT dir.c::__func__.3 2 OBJECT driver.c::__func__.0 2 OBJECT fib_rules.c::__msg.0 2 OBJECT file.c::__func__.2 2 OBJECT file.c::__key.1 2 OBJECT file.c::__key.2 2 OBJECT hpet.c::__func__.4 2 OBJECT icmp.c::__func__.1 2 OBJECT inode.c::__func__.1 2 OBJECT inode.c::__func__.3 2 OBJECT intel.c::__already_done.10 2 OBJECT intel.c::__already_done.11 2 OBJECT intel.c::__already_done.13 2 OBJECT ioctl.c::__func__.0 2 OBJECT iommu.c::__already_done.15 2 OBJECT iommu.c::__func__.10 2 OBJECT iommu.c::__func__.2 2 OBJECT iommu.c::_rs.13 2 OBJECT iommu.c::_rs.5 2 OBJECT iommu.c::_rs.9 2 OBJECT irq.c::__func__.0 2 OBJECT irq.c::__func__.2 2 OBJECT irqdomain.c::__func__.0 2 OBJECT irqdomain.c::__func__.1 2 OBJECT irqdomain.c::__func__.3 2 OBJECT main.c::__func__.10 2 OBJECT main.c::__func__.11 2 OBJECT main.c::__func__.3 2 OBJECT main.c::__func__.4 2 OBJECT main.c::__func__.5 2 OBJECT manage.c::__func__.1 2 OBJECT mount.c::__func__.0 2 OBJECT msr.c::__func__.0 2 OBJECT ping.c::__func__.1 2 OBJECT property.c::__func__.3 2 OBJECT qos.c::__func__.0 2 OBJECT qos.c::__func__.2 2 OBJECT resource.c::__func__.1 2 OBJECT route.c::__key.0 2 OBJECT route.c::__msg.1 2 OBJECT route.c::__msg.2 2 OBJECT route.c::__msg.3 2 OBJECT route.c::__msg.4 2 OBJECT route.c::__msg.5 2 OBJECT route.c::__msg.6 2 OBJECT swap.c::__func__.0 2 OBJECT syncookies.c::___done.1 2 OBJECT syncookies.c::msstab 2 OBJECT syncookies.c::___once_key.2 2 OBJECT sysfs.c::dev_attr_name 2 OBJECT sysfs.c::__key.1 2 OBJECT sysfs.c::power_attrs 2 OBJECT udp.c::descriptor.12 2 OBJECT udp.c::descriptor.13 2 OBJECT udp.c::__func__.2 2 OBJECT udp.c::__func__.3 2 OBJECT udp.c::__func__.4 2 OBJECT utils.c::__func__.5 3 FUNC core.c::cmask_show 3 FUNC core.c::edge_show 3 FUNC core.c::event_show 3 FUNC core.c::inv_show 3 FUNC core.c::umask_show 3 FUNC inode.c::init_once 3 OBJECT acpi.c::__func__.1 3 OBJECT core.c::format_attr_cmask 3 OBJECT core.c::format_attr_edge 3 OBJECT core.c::format_attr_event 3 OBJECT core.c::format_attr_inv 3 OBJECT core.c::format_attr_umask 3 OBJECT core.c::__func__.6 3 OBJECT core.c::__func__.8 3 OBJECT file.c::__key.3 3 OBJECT generic.c::__func__.0 3 OBJECT iommu.c::__func__.0 3 OBJECT iommu.c::__func__.1 3 OBJECT iommu.c::__func__.8 3 OBJECT main.c::__func__.0 3 OBJECT main.c::__func__.1 3 OBJECT main.c::__func__.6 3 OBJECT quirks.c::__func__.0 3 OBJECT sysfs.c::__func__.0 4 OBJECT core.c::__func__.4 5 OBJECT inode.c::tokens 6 OBJECT core.c::__func__.3 6 OBJECT core.c::__func__.5 7 OBJECT core.c::__func__.1 8 OBJECT core.c::__func__.0 8 OBJECT core.c::__func__.2
We could probably minimize the FUNC duplicates with unique names, but I'm not as optimistic about the OBJECTs as most are created via macros like __already_done.X. Unless clever macro magic?
Next question: what are the odds that these entries, at least the ones we can't easily rename, need disambiguity for livepatching? or kpatch-build for related purposes?
-- Joe
| |