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    Subject[PATCH 5.4 16/60] mips: vdso: add build time check that no jalr t9 calls left
    Date
    From: Victor Kamensky <kamensky@cisco.com>

    [ Upstream commit 976c23af3ee5bd3447a7bfb6c356ceb4acf264a6 ]

    vdso shared object cannot have GOT based PIC 'jalr t9' calls
    because nobody set GOT table in vdso. Contributing into vdso
    .o files are compiled in PIC mode and as result for internal
    static functions calls compiler will generate 'jalr t9'
    instructions. Those are supposed to be converted into PC
    relative 'bal' calls by linker when relocation are processed.

    Mips global GOT entries do have dynamic relocations and they
    will be caught by cmd_vdso_check Makefile rule. Static PIC
    calls go through mips local GOT entries that do not have
    dynamic relocations. For those 'jalr t9' calls could be present
    but without dynamic relocations and they need to be converted
    to 'bal' calls by linker.

    Add additional build time check to make sure that no 'jalr t9'
    slip through because of some toolchain misconfiguration that
    prevents 'jalr t9' to 'bal' conversion.

    Signed-off-by: Victor Kamensky <kamensky@cisco.com>
    Signed-off-by: Paul Burton <paulburton@kernel.org>
    Cc: linux-mips@vger.kernel.org
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: James Hogan <jhogan@kernel.org>
    Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
    Cc: bruce.ashfield@gmail.com
    Cc: richard.purdie@linuxfoundation.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/mips/vdso/Makefile | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
    index b6b1eb638fb14..08c835d48520b 100644
    --- a/arch/mips/vdso/Makefile
    +++ b/arch/mips/vdso/Makefile
    @@ -92,12 +92,18 @@ CFLAGS_REMOVE_vdso.o = -pg
    GCOV_PROFILE := n
    UBSAN_SANITIZE := n

    +# Check that we don't have PIC 'jalr t9' calls left
    +quiet_cmd_vdso_mips_check = VDSOCHK $@
    + cmd_vdso_mips_check = if $(OBJDUMP) --disassemble $@ | egrep -h "jalr.*t9" > /dev/null; \
    + then (echo >&2 "$@: PIC 'jalr t9' calls are not supported"; \
    + rm -f $@; /bin/false); fi
    +
    #
    # Shared build commands.
    #

    quiet_cmd_vdsold_and_vdso_check = LD $@
    - cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check)
    + cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check); $(cmd_vdso_mips_check)

    quiet_cmd_vdsold = VDSO $@
    cmd_vdsold = $(CC) $(c_flags) $(VDSO_LDFLAGS) \
    --
    2.20.1


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