Josh Poimboeuf b13aca7cde create-diff-object: Don't strip callback symbols ... We saw the following panic on ppc64le when loading the macro-callbacks integration test: livepatch: enabling patch 'kpatch_macro_callbacks' Oops: Exception in kernel mode, sig: 4 [#1] LE SMP NR_CPUS=2048 NUMA pSeries Modules linked in: kpatch_macro_callbacks(OEK+) rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace fscache sunrpc sg pseries_rng xts vmx_crypto xfs libcrc32c sd_mod ibmvscsi scsi_transport_srp ibmveth dm_mirror dm_region_hash dm_log dm_mod [last unloaded: kpatch_gcc_static_local_var_6] CPU: 2 PID: 17445 Comm: insmod Kdump: loaded Tainted: G OE K --------- - - 4.18.0-128.el8.ppc64le #1 NIP: d00000000bb708e0 LR: c0000000001fd610 CTR: d00000000bb708e0 REGS: c00000040e98f640 TRAP: 0700 Tainted: G OE K --------- - - (4.18.0-128.el8.ppc64le) MSR: 800000000288b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 28008228 XER: 20040003 CFAR: c0000000001fd60c IRQMASK: 0 GPR00: c0000000001fd5c0 c00000040e98f8c0 c000000001662a00 c000000733525400 GPR04: 0000000000000800 0000000000000800 c0000000015e2c00 c0000007335254a8 GPR08: 0000000000000001 d00000000bb708e0 c0000007eeb68400 0000000000000000 GPR12: d00000000bb708e0 c000000007fad600 0000000000000001 aaaaaaaaaaaaaaab GPR16: 000000000000ff20 000000000000fff1 000000000000fff2 d00000000bb90000 GPR20: 00000000000000a9 c00000040e98fc00 c000000000d8a728 c00000040e98fc00 GPR24: d00000000bb73f88 00000000006080c0 d00000000bb73a38 c000000733525400 GPR28: 0000000000000001 c000000733525400 ffffffffffffffed c0000007eeb60900 NIP [d00000000bb708e0] callback_info.isra.0+0x7c/0x66c [kpatch_macro_callbacks] LR [c0000000001fd610] __klp_enable_patch+0x130/0x230 Call Trace: [c00000040e98f8c0] [c0000000001fd5c0] __klp_enable_patch+0xe0/0x230 (unreliable) [c00000040e98f940] [c0000000001fd7d8] klp_enable_patch+0xc8/0x100 [c00000040e98f980] [d00000000bb7079c] patch_init+0x460/0x4cc [kpatch_macro_callbacks] [c00000040e98fa20] [c000000000010108] do_one_initcall+0x58/0x248 [c00000040e98fae0] [c00000000023b860] do_init_module+0x80/0x330 [c00000040e98fb70] [c0000000002416a4] load_module+0x3994/0x3d00 [c00000040e98fd30] [c000000000241cf4] sys_finit_module+0xc4/0x130 [c00000040e98fe30] [c00000000000b388] system_call+0x5c/0x70 Instruction dump: 7cea482a 48000235 e8410018 48000014 3c620000 e8638160 48000221 e8410018 38210060 e8010010 7c0803a6 4e800020 <0000ae18> 00000000 3c4c0001 3842ae18 The problem was introduced by a recent fix: e8f7f2dfe8 ("create-diff-object/ppc64le: Fix replace_sections_syms() for bundled symbols") We didn't notice the fact that there's a hack in kpatch_include_callback_elements() which reverts the work of kpatch_replace_sections_syms() for callback function symbols. The problem is that that revert is only partial, causing the callback pointers to point to the .TOC data which is located 8 bytes before the start of the function code. This happens because kpatch_include_callback_elements() makes the same assumption that kpatch_replace_sections_syms() had previously made: that bundled symbols are always located at the start of their corresponding sections. kpatch_include_callback_elements() mysteriously strips references to the callback function symbols, replacing them with section symbols. In this case it replaced a 'pre_patch_callback' function reference with a '.text.unlikely.pre_patch_callback' section reference. But it didn't adjust the rela->addend accordingly. Joe discovered the reasoning for why kpatch_include_callback_elements() removes function symbol references in the commit log for 7dfad2fb76 ("fix dynrela corruption in load/unload hooks"): In the case of the hook functions, we strip the FUNC symbol to prevent it from being added to the kpatch.funcs section as a patched function. But that justification doesn't really make sense, at least not with the current code. Callbacks aren't added to .kpatch.funcs anyway. They're classifed as NEW. Only CHANGED functions are added to .kpatch.funcs. So remove that hack, fixing this bug in the process. This does have a side effect of showing the callback functions as new functions, because their symbols are now included. Before: aio.o: found callback: post_unpatch_callback aio.o: found callback: pre_patch_callback aio.o: found callback: pre_unpatch_callback aio.o: new function: callback_info.isra.0 After: aio.o: found callback: post_unpatch_callback aio.o: found callback: pre_patch_callback aio.o: found callback: pre_unpatch_callback aio.o: new function: callback_info.isra.0 aio.o: new function: pre_patch_callback aio.o: new function: post_patch_callback aio.o: new function: pre_unpatch_callback aio.o: new function: post_unpatch_callback But anyway they _are_ new functions, so the new output seems more correct to me. Fixes: e8f7f2dfe8 ("create-diff-object/ppc64le: Fix replace_sections_syms() for bundled symbols") Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>		2019-08-15 15:08:31 -05:00
..
gcc-plugins	gcc-plugin: Include additional header for GCC 8	2018-05-30 19:39:48 +05:30
insn	insn: get it to compile in create-diff-object	2014-05-30 15:19:57 -05:00
create-diff-object.c	create-diff-object: Don't strip callback symbols	2019-08-15 15:08:31 -05:00
create-klp-module.c	create-klp-module: check symtab in main()	2019-08-05 12:10:47 +02:00
create-kpatch-module.c	create-kpatch-module: check symtab in main()	2019-08-05 12:10:47 +02:00
kpatch-build	kpatch-build: check if gcc supports -gz=none	2019-07-31 11:16:16 +03:00
kpatch-elf.c	kpatch-elf: add a couple mission section checks	2019-08-05 12:10:47 +02:00
kpatch-elf.h	create-diff-object: add symbol relations	2018-07-11 09:57:31 +02:00
kpatch-gcc	Making kpatch-build compatible with custom gcc names	2019-05-09 19:15:11 +02:00
kpatch-intermediate.h	create-klp-module: get rid of redundant kpatch_relocation.offset field	2017-11-09 19:16:14 -06:00
kpatch.h	kpatch-build: add exit status enum	2018-06-15 07:11:48 -04:00
list.h	new .fixup group size algorithm	2014-09-15 14:54:57 -05:00
log.h	kpatch-build: add exit status enum	2018-06-15 07:11:48 -04:00
lookup.c	lookup: exit on error in make_modname()	2019-08-05 12:10:47 +02:00
lookup.h	kpatch-build: use symbol table instead of kobject	2018-05-18 09:24:40 +02:00
Makefile	ppc64le: fix gcc-plugin installation	2018-04-19 10:16:37 +02:00