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    Subject[PATCH AUTOSEL 4.9 05/74] ARM: prevent tracing IPI_CPU_BACKTRACE
    Date
    From: Arnd Bergmann <arnd@arndb.de>

    [ Upstream commit be167862ae7dd85c56d385209a4890678e1b0488 ]

    Patch series "compiler: allow all arches to enable
    CONFIG_OPTIMIZE_INLINING", v3.

    This patch (of 11):

    When function tracing for IPIs is enabled, we get a warning for an
    overflow of the ipi_types array with the IPI_CPU_BACKTRACE type as
    triggered by raise_nmi():

    arch/arm/kernel/smp.c: In function 'raise_nmi':
    arch/arm/kernel/smp.c:489:2: error: array subscript is above array bounds [-Werror=array-bounds]
    trace_ipi_raise(target, ipi_types[ipinr]);

    This is a correct warning as we actually overflow the array here.

    This patch raise_nmi() to call __smp_cross_call() instead of
    smp_cross_call(), to avoid calling into ftrace. For clarification, I'm
    also adding a two new code comments describing how this one is special.

    The warning appears to have shown up after commit e7273ff49acf ("ARM:
    8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI"), which changed the
    number assignment from '15' to '8', but as far as I can tell has existed
    since the IPI tracepoints were first introduced. If we decide to
    backport this patch to stable kernels, we probably need to backport
    e7273ff49acf as well.

    [yamada.masahiro@socionext.com: rebase on v5.1-rc1]
    Link: http://lkml.kernel.org/r/20190423034959.13525-2-yamada.masahiro@socionext.com
    Fixes: e7273ff49acf ("ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI")
    Fixes: 365ec7b17327 ("ARM: add IPI tracepoints") # v3.17
    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Christophe Leroy <christophe.leroy@c-s.fr>
    Cc: Mathieu Malaterre <malat@debian.org>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Stefan Agner <stefan@agner.ch>
    Cc: Boris Brezillon <bbrezillon@kernel.org>
    Cc: Miquel Raynal <miquel.raynal@bootlin.com>
    Cc: Richard Weinberger <richard@nod.at>
    Cc: David Woodhouse <dwmw2@infradead.org>
    Cc: Brian Norris <computersforpeace@gmail.com>
    Cc: Marek Vasut <marek.vasut@gmail.com>
    Cc: Russell King <rmk+kernel@arm.linux.org.uk>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm/include/asm/hardirq.h | 1 +
    arch/arm/kernel/smp.c | 6 +++++-
    2 files changed, 6 insertions(+), 1 deletion(-)

    diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h
    index 3d7351c844aac..2fd0a2619b0b3 100644
    --- a/arch/arm/include/asm/hardirq.h
    +++ b/arch/arm/include/asm/hardirq.h
    @@ -5,6 +5,7 @@
    #include <linux/threads.h>
    #include <asm/irq.h>

    +/* number of IPIS _not_ including IPI_CPU_BACKTRACE */
    #define NR_IPI 7

    typedef struct {
    diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
    index 7a5dc011c5230..deea60f01d245 100644
    --- a/arch/arm/kernel/smp.c
    +++ b/arch/arm/kernel/smp.c
    @@ -75,6 +75,10 @@ enum ipi_msg_type {
    IPI_CPU_STOP,
    IPI_IRQ_WORK,
    IPI_COMPLETION,
    + /*
    + * CPU_BACKTRACE is special and not included in NR_IPI
    + * or tracable with trace_ipi_*
    + */
    IPI_CPU_BACKTRACE,
    /*
    * SGI8-15 can be reserved by secure firmware, and thus may
    @@ -801,7 +805,7 @@ core_initcall(register_cpufreq_notifier);

    static void raise_nmi(cpumask_t *mask)
    {
    - smp_cross_call(mask, IPI_CPU_BACKTRACE);
    + __smp_cross_call(mask, IPI_CPU_BACKTRACE);
    }

    void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
    --
    2.20.1
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