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scripts/kallsyms.c: ignore symbol type 'n' 

gcc on aarch64 may emit synbols of type 'n' if the kernel is built with
'-frecord-gcc-switches'.  In most cases, those symbols are reported with
nm as

	000000000000000e n $d

and with objdump as

	0000000000000000 l    d  .GCC.command.line	0000000000000000 .GCC.command.line
	000000000000000e l       .GCC.command.line	0000000000000000 $d

Those symbols are detected in is_arm_mapping_symbol() and ignored.
However, if "--prefix-symbols=<prefix>" is configured as well, the
situation is different.  For example, in efi/libstub, arm64 images are
built with

	'--prefix-alloc-sections=.init --prefix-symbols=__efistub_'.

In combination with '-frecord-gcc-switches', the symbols are now reported
by nm as:

	000000000000000e n __efistub_$d
and by objdump as:
	0000000000000000 l    d  .GCC.command.line	0000000000000000 .GCC.command.line
	000000000000000e l       .GCC.command.line	0000000000000000 __efistub_$d

Those symbols are no longer ignored and included in the base address
calculation.  This results in a base address of 000000000000000e, which
in turn causes kallsyms to abort with

    kallsyms failure:
	relative symbol value 0xffffff900800a000 out of range in relative mode

The problem is seen in little endian arm64 builds with CONFIG_EFI
enabled and with '-frecord-gcc-switches' set in KCFLAGS.

Explicitly ignore symbols of type 'n' since those are clearly debug
symbols.

Link: http://lkml.kernel.org/r/1507136063-3139-1-git-send-email-linux@roeck-us.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Guenter Roeck 2017-10-13 15:57:58 -07:00 committed by Linus Torvalds
parent 7ddd8faf43
commit 51962a9d43
1 changed files with 1 additions and 1 deletions
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2
scripts/kallsyms.c
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@ -158,7 +158,7 @@ static int read_symbol(FILE *in, struct sym_entry *s)
else if (str[0] == '$')
return -1;
/* exclude debugging symbols */
else if (stype == 'N')
else if (stype == 'N' || stype == 'n')
return -1;
/* include the type field in the symbol name, so that it gets