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    Subject[PATCH 4.4 81/92] s390: move spectre sysfs attribute code
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Martin Schwidefsky <schwidefsky@de.ibm.com>

    [ Upstream commit 4253b0e0627ee3461e64c2495c616f1c8f6b127b ]

    The nospec-branch.c file is compiled without the gcc options to
    generate expoline thunks. The return branch of the sysfs show
    functions cpu_show_spectre_v1 and cpu_show_spectre_v2 is an indirect
    branch as well. These need to be compiled with expolines.

    Move the sysfs functions for spectre reporting to a separate file
    and loose an '.' for one of the messages.

    Cc: stable@vger.kernel.org # 4.16
    Fixes: d424986f1d ("s390: add sysfs attributes for spectre")
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/s390/kernel/Makefile | 1 +
    arch/s390/kernel/nospec-branch.c | 18 ------------------
    arch/s390/kernel/nospec-sysfs.c | 21 +++++++++++++++++++++
    3 files changed, 22 insertions(+), 18 deletions(-)
    create mode 100644 arch/s390/kernel/nospec-sysfs.c

    --- a/arch/s390/kernel/Makefile
    +++ b/arch/s390/kernel/Makefile
    @@ -49,6 +49,7 @@ obj-y += nospec-branch.o

    extra-y += head.o head64.o vmlinux.lds

    +obj-$(CONFIG_SYSFS) += nospec-sysfs.o
    CFLAGS_REMOVE_nospec-branch.o += $(CC_FLAGS_EXPOLINE)

    obj-$(CONFIG_MODULES) += s390_ksyms.o module.o
    --- a/arch/s390/kernel/nospec-branch.c
    +++ b/arch/s390/kernel/nospec-branch.c
    @@ -44,24 +44,6 @@ static int __init nospec_report(void)
    }
    arch_initcall(nospec_report);

    -#ifdef CONFIG_SYSFS
    -ssize_t cpu_show_spectre_v1(struct device *dev,
    - struct device_attribute *attr, char *buf)
    -{
    - return sprintf(buf, "Mitigation: __user pointer sanitization\n");
    -}
    -
    -ssize_t cpu_show_spectre_v2(struct device *dev,
    - struct device_attribute *attr, char *buf)
    -{
    - if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
    - return sprintf(buf, "Mitigation: execute trampolines\n");
    - if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
    - return sprintf(buf, "Mitigation: limited branch prediction.\n");
    - return sprintf(buf, "Vulnerable\n");
    -}
    -#endif
    -
    #ifdef CONFIG_EXPOLINE

    int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);
    --- /dev/null
    +++ b/arch/s390/kernel/nospec-sysfs.c
    @@ -0,0 +1,21 @@
    +// SPDX-License-Identifier: GPL-2.0
    +#include <linux/device.h>
    +#include <linux/cpu.h>
    +#include <asm/facility.h>
    +#include <asm/nospec-branch.h>
    +
    +ssize_t cpu_show_spectre_v1(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + return sprintf(buf, "Mitigation: __user pointer sanitization\n");
    +}
    +
    +ssize_t cpu_show_spectre_v2(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
    + return sprintf(buf, "Mitigation: execute trampolines\n");
    + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
    + return sprintf(buf, "Mitigation: limited branch prediction\n");
    + return sprintf(buf, "Vulnerable\n");
    +}

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