From: Arnd Bergmann <arnd@xxxxxxxx> 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 patch 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. 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@xxxxxxxx> [yamada.masahiro@xxxxxxxxxxxxx: rebase on v5.1-rc1] Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> --- This is a long-standing issue, and Arnd posted this patch two years ago: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/409393.html It is no longer applied, so I rebased it on top of the latest kernel. Changes in v3: None Changes in v2: None 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 cba23eaa6072..7a88f160b1fb 100644 --- a/arch/arm/include/asm/hardirq.h +++ b/arch/arm/include/asm/hardirq.h @@ -6,6 +6,7 @@ #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 facd4240ca02..c93fe0f256de 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -70,6 +70,10 @@ 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 @@ -797,7 +801,7 @@ 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) -- 2.17.1