When building the 32-bit VDSO, we are building 32-bit code as part of
a 64-bit kernel build. That requires us to tweak the cflags to trick
the compiler into building 32-bit code for us. The main way we do that
is by passing -m32, but there are other options that affect code
generation and ABI selection.
In particular when building vgettimeofday.c, we end up passing
-mcall-aixdesc because it's in KBUILD_CFLAGS, which causes the
compiler to generate function descriptors, and dot symbols, eg:
$ nm arch/powerpc/kernel/vdso32/vgettimeofday.o
000005d0 T .__c_kernel_clock_getres
00000024 D __c_kernel_clock_getres
...
We get away with that at the moment because we also use the DOTSYM
macro, and that is also incorrectly prepending a '.' in 32-bit VDSO
code due to a separate bug.
But we shouldn't be generating function descriptors for this file,
there's no 32-bit ABI that includes function descriptors, so the
resulting object file is some frankenstein and it's surprising that it
even links.
So filter out all the ABI-related options we add to CFLAGS for 64-bit
builds, so that they're not used when building 32-bit code. With that
we only see regular text symbols:
$ nm arch/powerpc/kernel/vdso32/vgettimeofday.o michael@alpine1-p1
000005d0 T __c_kernel_clock_getres
00000000 T __c_kernel_clock_gettime
00000200 T __c_kernel_clock_gettime64
00000410 T __c_kernel_gettimeofday
00000650 T __c_kernel_time
Fixes: ab037dd87a ("powerpc/vdso: Switch VDSO to generic C implementation.")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201218111619.1206391-2-mpe@ellerman.id.au
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