ERROR: meminfo.o: 1 function(s) can not be patched

[aliceinwire]

No description provided.

[aliceinwire]

Building modules, stage 2.
MODPOST 259 modules
ERROR: meminfo.o: 1 function(s) can not be patched
meminfo.o: function meminfo_proc_show has no fentry/mcount call, unable to patch
/usr/libexec/kpatch/create-diff-object: unreconcilable difference

[joe-lawrence]

I would first check your kernel .config file. kpatch-build already checks for a bunch of settings... I would have thought CONFIG_LIVEPATCH would be enough to enable most of the dependencies like CONFIG_FUNCTION_TRACER though.

[aliceinwire]

maybe would be useful if also kpatch-build could check for the kernel configurations settings and not only during compilation time when compiling core.c
https://github.com/dynup/kpatch/blob/1fa1e7a05a245d78b5326bb45eed0b413ce3c1bd/kmod/core/core.c#L57
the only check for CONFIG_LIVEPATCH is here: https://github.com/dynup/kpatch/blob/master/kpatch-build/kpatch-build#L666
and if there is no CONFIG_LIVEPATCH is preparing for using kpatch core module but maybe would be nice to check at least for FTRACE options.

[aliceinwire]

Building modules, stage 2.
MODPOST 259 modules
Extracting new and modified ELF sections
meminfo.o: changed function: meminfo_proc_show
/usr/libexec/kpatch/create-diff-object: ERROR: meminfo.o: kpatch_check_relocations: 1941: out-of-range relocation .debug_str+9668 in .rela.debug_info

[aliceinwire]

create-diff-object debug output
create-diff-patch.log

[aliceinwire]

this is the patch tested:

diff -Nupr src.orig/fs/proc/meminfo.c src/fs/proc/meminfo.c
--- src.orig/fs/proc/meminfo.c  2017-11-17 15:58:41.113211972 -0500
+++ src/fs/proc/meminfo.c       2017-11-17 15:58:58.554211972 -0500
@@ -42,6 +42,8 @@ static void show_val_kb(struct seq_file
		seq_write(m, " kB\n", 4);
 }

+static int foo = 5;
+
 static int meminfo_proc_show(struct seq_file *m, void *v)
 {
		struct sysinfo i;
@@ -153,6 +155,7 @@ static int meminfo_proc_show(struct seq_
		show_val_kb(m, "CmaFree:        ",
					global_page_state(NR_FREE_CMA_PAGES));
 #endif
+       seq_printf(m, "kpatch: %d\n", foo);

		hugetlb_report_meminfo(m);


kpatch-build
	create-diff-object.c

[aliceinwire]

reported to kpatch upstream
kpatch issue #877