On Thu, Sep 01, 2022 at 01:39:02PM +1000, Michael Ellerman wrote: > Joe Lawrence <joe.lawrence@xxxxxxxxxx> writes: > > On Thu, Sep 01, 2022 at 08:30:44AM +1000, Michael Ellerman wrote: > >> Joe Lawrence <joe.lawrence@xxxxxxxxxx> writes: > ... > > > > Hi Michael, > > > > While we're on the topic of klp-relocations and Power, I saw a similar > > access problem when writing (late) relocations into > > .data..ro_after_init. I'm not entirely convinced this should be allowed > > (ie, is it really read-only after .init or ???), but it seems that other > > arches currently allow it ... > > I guess that's because we didn't properly fix apply_relocate_add() in > https://github.com/linuxppc/issues/issues/375 ? > > If other arches allow it then we don't want to be the odd one out :) > > So I guess we need to implement it. > FWIW, I think it this particular relocation is pretty rare, we haven't seen it in real patches nor do we have a kpatch test that generates it. I only hit a crash as I was trying to write a more exhaustive test for the klp-convert implementation. > > ===== TEST: klp-convert data relocations (late module patching) ===== > > % modprobe test_klp_convert_data > > livepatch: enabling patch 'test_klp_convert_data' > > livepatch: 'test_klp_convert_data': starting patching transition > > livepatch: 'test_klp_convert_data': patching complete > > % modprobe test_klp_convert_mod > > ... > > module_64: Applying ADD relocate section 54 to 20 > > module_64: RELOC at 000000008482d02a: 38-type as .klp.sym.test_klp_convert_mod.static_ro_after_init,0 (0xc0080000016d0084) + 0 > > BUG: Unable to handle kernel data access on write at 0xc0080000021d0000 > > Faulting instruction address: 0xc000000000055f14 > > Oops: Kernel access of bad area, sig: 11 [#1] > > LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries > > Modules linked in: test_klp_convert_mod(+) test_klp_convert_data(K) bonding rfkill tls pseries_rng drm fuse drm_panel_orientation_quirks xfs libcrc32c sd_mod t10_pi sg ibmvscsi ibmveth scsi_transport_srp vmx_crypto dm_mirror dm_region_hash dm_log dm_mod [last unloaded: test_klp_convert_mod] > > CPU: 0 PID: 17089 Comm: modprobe Kdump: loaded Tainted: G K 5.19.0+ #1 > > NIP: c000000000055f14 LR: c00000000021ef28 CTR: c000000000055f14 > > REGS: c0000000387af5a0 TRAP: 0300 Tainted: G K (5.19.0+) > > MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 88228444 XER: 00000000 > > CFAR: c000000000055e04 DAR: c0080000021d0000 DSISR: 42000000 IRQMASK: 0 > > GPR00: c00000000021ef28 c0000000387af840 c000000002a68a00 c0000000088b3000 > > GPR04: c008000002230084 0000000000000026 0000000000000036 c0080000021e0480 > > GPR08: 000000007c426214 c000000000055f14 c000000000055e08 0000000000000d80 > > GPR12: c00000000021d9b0 c000000002d90000 c0000000088b3000 c0080000021f0810 > > GPR16: c0080000021c0638 c0000000088b3d80 00000000ffffffff c000000001181e38 > > GPR20: c0000000029dc088 c0080000021e0480 c0080000021f0870 aaaaaaaaaaaaaaab > > GPR24: c0000000088b3c40 c0080000021d0000 c0080000021f0000 0000000000000000 > > GPR28: c0080000021d0000 0000000000000000 c0080000021c0638 0000000000000810 > > NIP [c000000000055f14] apply_relocate_add+0x474/0x9e0 > > LR [c00000000021ef28] klp_apply_section_relocs+0x208/0x2d0 > > Call Trace: > > [c0000000387af840] [c0000000387af920] 0xc0000000387af920 (unreliable) > > [c0000000387af940] [c00000000021ef28] klp_apply_section_relocs+0x208/0x2d0 > > [c0000000387afa30] [c00000000021f080] klp_init_object_loaded+0x90/0x1e0 > > [c0000000387afac0] [c0000000002200ac] klp_module_coming+0x3dc/0x5c0 > > [c0000000387afb70] [c000000000231414] load_module+0xf64/0x13a0 > > [c0000000387afc90] [c000000000231b8c] __do_sys_finit_module+0xdc/0x180 > > [c0000000387afdb0] [c00000000002f004] system_call_exception+0x164/0x340 > > [c0000000387afe10] [c00000000000be68] system_call_vectored_common+0xe8/0x278 > > --- interrupt: 3000 at 0x7fffb6af4710 > > NIP: 00007fffb6af4710 LR: 0000000000000000 CTR: 0000000000000000 > > REGS: c0000000387afe80 TRAP: 3000 Tainted: G K (5.19.0+) > > MSR: 800000000000f033 <SF,EE,PR,FP,ME,IR,DR,RI,LE> CR: 48224244 XER: 00000000 > > IRQMASK: 0 > > GPR00: 0000000000000161 00007fffe06f5550 00007fffb6bf7200 0000000000000005 > > GPR04: 0000000105f36ca0 0000000000000000 0000000000000005 0000000000000000 > > GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > > GPR12: 0000000000000000 00007fffb738c540 0000000000000020 0000000000000000 > > GPR16: 0000010024d31de0 0000000000000000 0000000105f37d50 0000010024d302f8 > > GPR20: 0000000000000001 0000000000000908 0000010024d32020 0000010024d319b0 > > GPR24: 0000000000000000 0000000000000000 0000010024d32040 0000010024d303f0 > > GPR28: 0000010024d31e00 0000000105f36ca0 0000000000040000 0000010024d319b0 > > NIP [00007fffb6af4710] 0x7fffb6af4710 > > LR [0000000000000000] 0x0 > > --- interrupt: 3000 > > Instruction dump: > > 0000061c 0000061c 0000061c 0000061c 0000061c 0000061c 0000061c 0000061c > > 00000288 00000248 60000000 7c992050 <7c9ce92a> 60000000 60000000 e9310020 > > ---[ end trace 0000000000000000 ]--- > > > > $ readelf --wide --sections lib/livepatch/test_klp_convert_data.ko | grep -e '\[20\]' -e '\[54\]' > > [20] .data..ro_after_init PROGBITS 0000000000000000 001a58 000008 00 WA 0 0 8 > > [54] .klp.rela.test_klp_convert_mod..data..ro_after_init RELA 0000000000000000 0426e8 000018 18 Ao 49 20 8 > > > > I can push a branch up to github if you'd like to try it yourself. > > That would help thanks. > This branch should do it: https://github.com/joe-lawrence/klp-convert-tree/tree/klp-convert-v7-devel Boot that and then run tools/testing/selftests/livepatch/test-livepatch.sh -- Joe
