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Subject[PATCH] scripts/kallsyms: Ignore symbol type 'n'
Date
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.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
scripts/kallsyms.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 5d554419170b..9ee9bf7fd1a2 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -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
--
2.7.4
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