From b381a0cc0b900d042ff6a718ef9795101310d702 Mon Sep 17 00:00:00 2001 From: Kamalesh Babulal Date: Wed, 17 Jun 2020 19:51:56 +0530 Subject: [PATCH] lookup: Add __UNIQUE_ID_ to maybe_discarded_sym list Linux kernel tristate config options allows selected feature, either to be built-in to the kernel or to be built as a kernel module. When built as a kernel module, it's expected that the module, will be built with module information such as author, license, description and others. For each of the modinfo, a corresponding __UNIQUE_ID_ symbol is generated. Their lookup succeeds in the case of module but fails when selected to built-in to the kernel, the reason being that the kernel discards these __UNIQUE_ID_ symbols during linking. Add __UNIQUE_ID_ symbols to maybe_discarded_sym list, to avoid failure in case of table->object is vmlinux. i.e.: # cat .config|grep IOSCHED_BFQ (can be compiled as module too) CONFIG_IOSCHED_BFQ=y # readelf -sW ./block/bfq-iosched.o|grep UNIQUE 219: 0000000000000000 54 OBJECT LOCAL DEFAULT 267 __UNIQUE_ID_description223 220: 0000000000000036 16 OBJECT LOCAL DEFAULT 267 __UNIQUE_ID_license222 221: 0000000000000046 19 OBJECT LOCAL DEFAULT 267 __UNIQUE_ID_file221 222: 0000000000000059 25 OBJECT LOCAL DEFAULT 267 __UNIQUE_ID_author220 223: 0000000000000072 22 OBJECT LOCAL DEFAULT 267 __UNIQUE_ID_alias219 the line below before the kpatch error, is a debug printf to find the failing lookup symbol: Failed lookup for __UNIQUE_ID_description223 /root/kpatch/kpatch-build/create-diff-object: ERROR: bfq-iosched.o: find_local_syms: 180: couldn't find matching bfq-iosched.c local symbols in ./vmlinux symbol table with the patch, it successfully builds with both y/m config options: ... bfq-iosched.o: changed function: bfq_idle_slice_timer Patched objects: vmlinux Building patch module: livepatch-0001-block-bfq-fix-use-after-free-in-b.ko SUCCESS Signed-off-by: Kamalesh Babulal --- kpatch-build/lookup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c index 4f8c779..9086c9c 100644 --- a/kpatch-build/lookup.c +++ b/kpatch-build/lookup.c @@ -83,7 +83,8 @@ static int maybe_discarded_sym(const char *name) if (!strncmp(name, "__exitcall_", 11) || !strncmp(name, "__brk_reservation_fn_", 21) || !strncmp(name, "__func_stack_frame_non_standard_", 32) || - !strncmp(name, "__addressable_", 14)) + !strncmp(name, "__addressable_", 14) || + !strncmp(name, "__UNIQUE_ID_", 12)) return 1; return 0;