This is a note to let you know that I've just added the patch titled arm64: compat: fix vfp save/restore across signal handlers in big-endian to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-compat-fix-vfp-save-restore-across-signal-handlers-in-big-endian.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From bdec97a855ef1e239f130f7a11584721c9a1bf04 Mon Sep 17 00:00:00 2001 From: Will Deacon <will.deacon@xxxxxxx> Date: Tue, 15 Sep 2015 12:07:06 +0100 Subject: arm64: compat: fix vfp save/restore across signal handlers in big-endian From: Will Deacon <will.deacon@xxxxxxx> commit bdec97a855ef1e239f130f7a11584721c9a1bf04 upstream. When saving/restoring the VFP registers from a compat (AArch32) signal frame, we rely on the compat registers forming a prefix of the native register file and therefore make use of copy_{to,from}_user to transfer between the native fpsimd_state and the compat_vfp_sigframe. Unfortunately, this doesn't work so well in a big-endian environment. Our fpsimd save/restore code operates directly on 128-bit quantities (Q registers) whereas the compat_vfp_sigframe represents the registers as an array of 64-bit (D) registers. The architecture packs the compat D registers into the Q registers, with the least significant bytes holding the lower register. Consequently, we need to swap the 64-bit halves when converting between these two representations on a big-endian machine. This patch replaces the __copy_{to,from}_user invocations in our compat VFP signal handling code with explicit __put_user loops that operate on 64-bit values and swap them accordingly. Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/signal32.c | 47 ++++++++++++++++++++++++++++++++----------- 1 file changed, 36 insertions(+), 11 deletions(-) --- a/arch/arm64/kernel/signal32.c +++ b/arch/arm64/kernel/signal32.c @@ -212,14 +212,32 @@ int copy_siginfo_from_user32(siginfo_t * /* * VFP save/restore code. + * + * We have to be careful with endianness, since the fpsimd context-switch + * code operates on 128-bit (Q) register values whereas the compat ABI + * uses an array of 64-bit (D) registers. Consequently, we need to swap + * the two halves of each Q register when running on a big-endian CPU. */ +union __fpsimd_vreg { + __uint128_t raw; + struct { +#ifdef __AARCH64EB__ + u64 hi; + u64 lo; +#else + u64 lo; + u64 hi; +#endif + }; +}; + static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame) { struct fpsimd_state *fpsimd = ¤t->thread.fpsimd_state; compat_ulong_t magic = VFP_MAGIC; compat_ulong_t size = VFP_STORAGE_SIZE; compat_ulong_t fpscr, fpexc; - int err = 0; + int i, err = 0; /* * Save the hardware registers to the fpsimd_state structure. @@ -235,10 +253,15 @@ static int compat_preserve_vfp_context(s /* * Now copy the FP registers. Since the registers are packed, * we can copy the prefix we want (V0-V15) as it is. - * FIXME: Won't work if big endian. */ - err |= __copy_to_user(&frame->ufp.fpregs, fpsimd->vregs, - sizeof(frame->ufp.fpregs)); + for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) { + union __fpsimd_vreg vreg = { + .raw = fpsimd->vregs[i >> 1], + }; + + __put_user_error(vreg.lo, &frame->ufp.fpregs[i], err); + __put_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err); + } /* Create an AArch32 fpscr from the fpsr and the fpcr. */ fpscr = (fpsimd->fpsr & VFP_FPSCR_STAT_MASK) | @@ -263,7 +286,7 @@ static int compat_restore_vfp_context(st compat_ulong_t magic = VFP_MAGIC; compat_ulong_t size = VFP_STORAGE_SIZE; compat_ulong_t fpscr; - int err = 0; + int i, err = 0; __get_user_error(magic, &frame->magic, err); __get_user_error(size, &frame->size, err); @@ -273,12 +296,14 @@ static int compat_restore_vfp_context(st if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE) return -EINVAL; - /* - * Copy the FP registers into the start of the fpsimd_state. - * FIXME: Won't work if big endian. - */ - err |= __copy_from_user(fpsimd.vregs, frame->ufp.fpregs, - sizeof(frame->ufp.fpregs)); + /* Copy the FP registers into the start of the fpsimd_state. */ + for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) { + union __fpsimd_vreg vreg; + + __get_user_error(vreg.lo, &frame->ufp.fpregs[i], err); + __get_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err); + fpsimd.vregs[i >> 1] = vreg.raw; + } /* Extract the fpsr and the fpcr from the fpscr */ __get_user_error(fpscr, &frame->ufp.fpscr, err); Patches currently in stable-queue which might be from will.deacon@xxxxxxx are queue-4.2/arm64-head.s-initialise-mdcr_el2-in-el2_setup.patch queue-4.2/arm64-set-max_memblock_addr-according-to-linear-region-size.patch queue-4.2/arm64-kconfig-move-list_poison-to-a-safe-value.patch queue-4.2/arm64-flush-fp-simd-state-correctly-after-execve.patch queue-4.2/arm64-entry-always-restore-x0-from-the-stack-on-syscall-return.patch queue-4.2/kvm-arm64-add-workaround-for-cortex-a57-erratum-852523.patch queue-4.2/of-fdt-make-memblock-maximum-physical-address-arch-configurable.patch queue-4.2/arm64-errata-add-module-build-workaround-for-erratum-843419.patch queue-4.2/arm64-compat-fix-vfp-save-restore-across-signal-handlers-in-big-endian.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html