On Wed, Sep 16, 2020 at 11:19 PM Ard Biesheuvel ardb@kernel.org wrote:

Nick reports that the following error is produced in some cases when using GCC+ld.bfd to build the ARM defconfig with Thumb2 enabled:

arch/arm/vfp/vfphw.o: in function `vfp_support_entry': (.text+0xa): relocation truncated to fit: R_ARM_THM_JUMP19 against symbol `vfp_kmode_exception' defined in .text.unlikely section in arch/arm/vfp/vfpmodule.o

$ arm-linux-gnueabihf-ld --version GNU ld (GNU Binutils for Debian) 2.34

FWIW this was my compiler version, too: $ arm-linux-gnueabihf-gcc --version arm-linux-gnueabihf-gcc (Debian 9.3.0-8) 9.3.0

Generally, the linker should be able to fix up out of range branches by emitting veneers, but apparently, it fails to do so in this particular case, i.e., a conditional 'tail call' to vfp_kmode_exception(), which is not defined in the same object file.

So let's force the use of a non-conditional encoding of the B instruction, which has more space for an immediate offset.

Cc: stable@vger.kernel.org Reported-by: Nick Desaulniers ndesaulniers@google.com Tested-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Ard Biesheuvel ardb@kernel.org

---

arch/arm/vfp/vfphw.S | 1 + 1 file changed, 1 insertion(+)

diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index 4fcff9f59947..f1468702fbc9 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -82,6 +82,7 @@ ENTRY(vfp_support_entry) ldr r3, [sp, #S_PSR] @ Neither lazy restore nor FP exceptions and r3, r3, #MODE_MASK @ are supported in kernel mode teq r3, #USR_MODE +THUMB( it ne ) bne vfp_kmode_exception @ Returns through lr

    VFPFMRX r1, FPEXC               @ Is the VFP enabled?

-- 2.17.1