kallsyms: don't overload absolute symbol type for percpu symbols
Commit c6bda7c988a5 ("kallsyms: fix percpu vars on x86-64 with
relocation") overloaded the 'A' (absolute) symbol type to signify that a
symbol is not subject to dynamic relocation. However, the original A
type does not imply that at all, and depending on the version of the
toolchain, many A type symbols are emitted that are in fact relative to
the kernel text, i.e., if the kernel is relocated at runtime, these
symbols should be updated as well.
For instance, on sparc32, the following symbols are emitted as absolute
(kindly provided by Guenter Roeck):
f035a420 A _etext
f03d9000 A _sdata
f03de8c4 A jiffies
f03f8860 A _edata
f03fc000 A __init_begin
f041bdc8 A __init_text_end
f0423000 A __bss_start
f0423000 A __init_end
f044457d A __bss_stop
f044457d A _end
On x86_64, similar behavior can be observed:
ffffffff81a00000 A __end_rodata_hpage_align
ffffffff81b19000 A __vvar_page
ffffffff81d3d000 A _end
Even if only a couple of them pass the symbol range check that results
in them to be taken into account for the final kallsyms symbol table, it
is obvious that 'A' does not mean the symbol does not need to be updated
at relocation time, and overloading its meaning to signify that is
perhaps not a good idea.
So instead, add a new percpu_absolute member to struct sym_entry, and
when --absolute-percpu is in effect, use it to record symbols whose
addresses should be emitted as final values rather than values that
still require relocation at runtime. That way, we can drop the check
against the 'A' type.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Marek <mmarek@suse.cz>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 file changed