| Message ID | 1539851039-15778-1-git-send-email-zhang.chunyan@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM: prevent tracing IPI_CPU_BACKTRACE | expand |
Hi, On 18/10/2018 09:23, Chunyan Zhang wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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. > > Resubmitting this patch is because that I found coverity is complaining > the issue this patch fixed, and also I got the traces like below: > "ipi_raise: target_mask=00000001 (machine_suspend)" which actually was > the TPS of suspend_resume[1] rather that ipi_raise. > What's the status on this patch? it does not seem to be in v5.0-rc3 nor linux-next and looks like an actual issue. Also, I'm assuming the patch is avoiding the tracing of IPI_CPU_BACKTRACE because the tracing is not NMI safe. It would be good to have a comment about that either near NR_IPI or ipi_types stating why this IPI is excluded. Thanks, > [1] > https://elixir.bootlin.com/linux/latest/source/kernel/power/suspend.c#L80 > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Fixes: e7273ff49acf ("ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI") > Fixes: 365ec7b17327 ("ARM: add IPI tracepoints") # v3.17 > Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.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 cba23ea..7a88f16 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 0978282..ddd48e2 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 > @@ -755,7 +759,7 @@ 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) >
diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h index cba23ea..7a88f16 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 0978282..ddd48e2 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 @@ -755,7 +759,7 @@ 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)