On Tue, Feb 16, 2021 at 09:56:32AM -0800, 'Nick Desaulniers' via Clang Built Linux wrote:

On Tue, Feb 16, 2021 at 12:55 AM Alexander Lobakin [off-list ref] wrote:

quoted

LKP triggered lots of LD orphan warnings [0]:

Thanks for the patch, just some questions.

With which linker?  Was there a particular config from the bot's
report that triggered this?

Looks like GNU ld 2.34 (see below).

quoted

mipsel-linux-ld: warning: orphan section `.data.$Lubsan_data299' from
`init/do_mounts_rd.o' being placed in section `.data.$Lubsan_data299'
mipsel-linux-ld: warning: orphan section `.data.$Lubsan_data183' from
`init/do_mounts_rd.o' being placed in section `.data.$Lubsan_data183'
mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type3' from
`init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type3'
mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type2' from
`init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type2'
mipsel-linux-ld: warning: orphan section `.data.$Lubsan_type0' from
`init/do_mounts_rd.o' being placed in section `.data.$Lubsan_type0'

[...]

Seems like "unnamed data" isn't the only type of symbols that UBSAN
instrumentation can emit.
Catch these into .data with the wildcard as well.

[0] https://lore.kernel.org/linux-mm/202102160741.k57GCNSR-lkp@intel.com (local)

Fixes: f41b233de0ae ("vmlinux.lds.h: catch UBSAN's "unnamed data" into data")
Reported-by: kernel test robot <redacted>
Signed-off-by: Alexander Lobakin <redacted>
---
 include/asm-generic/vmlinux.lds.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index cc659e77fcb0..83537e5ee78f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h

@@ -95,7 +95,7 @@
  */
 #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
 #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_*
+#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$Lubsan_*

Are these sections only created when
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is selected?  (Same with
.data.$__unnamed_*)

Most likely, as that config is set in the problematic config. My guess
is that these are GCC's equivalent of Clang's .data.$__unnamed_...

$ crl https://lore.kernel.org/linux-mm/202102160741.k57GCNSR-lkp@intel.com/2-a.bin (local) | gzip -d | rg "CONFIG_LD_DEAD_CODE|CONFIG_LD_VERSION"
CONFIG_LD_VERSION=234000000
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y

quoted

 #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
 #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
 #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
--
2.30.1

-- 
Thanks,
~Nick Desaulniers