The PLT code uses a separate .init.plt section to allocate PLT entries
for jump and call instructions in __init code. However, even for fairly
sizable modules like mac80211.ko, we only end up with a couple of PLT
entries in the .init section, and so we can simplify the code
significantly by emitting all PLT entries into the same section.
Tested-by: Jongsung Kim <neidhard.kim@lge.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Loading modules far away from the kernel in memory is problematic
because the 'bl' instruction only has limited reach, and modules are not
built with PLTs. Instead of using the -mlong-calls option (which affects
all compiler emitted bl instructions, but not the ones in assembler),
this patch allocates some additional space at module load time, and
populates it with PLT like veneers when encountering relocations that
are out of range.
This should work with all relocations against symbols exported by the
kernel, including those resulting from GCC generated implicit function
calls for ftrace etc.
The module memory size increases by about 5% on average, regardless of
whether any PLT entries were actually needed. However, due to the page
based rounding that occurs when allocating module memory, the average
memory footprint increase is negligible.
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Ard Biesheuvel