| Message ID | 1455804123-2526139-3-git-send-email-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
| Series | [1/9] ARM: ARMv7-M uses BE-8, not BE-32 | expand |
Hi, Any conclusion on this patch? The coverity tool is still complaining error on the issue which this patch can fix. Thanks, Chunyan On 18 February 2016 at 23:18, Arnd Bergmann <arnd@arndb.de> wrote: > On Thursday 18 February 2016 14:37:09 Russell King - ARM Linux wrote: >> On Thu, Feb 18, 2016 at 03:01:54PM +0100, Arnd Bergmann wrote: >> > 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]); >> >> We really don't want to treat the backtrace IPI as a normal IPI at all - >> we want it to invoke the least amount of code possible. Hence this code >> which avoids the issue: >> >> if ((unsigned)ipinr < NR_IPI) { >> trace_ipi_entry_rcuidle(ipi_types[ipinr]); >> __inc_irq_stat(cpu, ipi_irqs[ipinr]); >> } >> >> However, what's missing is that the addition of tracing here missed >> that CPU_BACKTRACE is not to be traced. The call in raise_nmi() >> should have been converted to __smp_cross_call() to avoid the >> tracing code. > > I've replaced the patch locally with the version below now, and > will throw it into the randconfig build test infrastructure to > make sure I didn't screw up in an obvious way here. > > Arnd > > From 7528c9b0558fdf4de785e62e61f0dd2ffe874110 Mon Sep 17 00:00:00 2001 > From: Arnd Bergmann <arnd@arndb.de> > Date: Sun, 31 Jan 2016 22:26:21 +0100 > Subject: [PATCH] ARM: prevent tracing IPI_CPU_BACKTRACE > > 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. > > 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: Arnd Bergmann <arnd@arndb.de> > > diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h > index 3d7351c844aa..2fd0a2619b0b 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 b4048e370730..9802a94260db 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -72,6 +72,10 @@ 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 > @@ -757,7 +761,7 @@ static void raise_nmi(cpumask_t *mask) > if (cpumask_test_cpu(smp_processor_id(), mask) && irqs_disabled()) > nmi_cpu_backtrace(NULL); > > - smp_cross_call(mask, IPI_CPU_BACKTRACE); > + __smp_cross_call(mask, IPI_CPU_BACKTRACE); > } > > void arch_trigger_all_cpu_backtrace(bool include_self) > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm/include/asm/hardirq.h b/arch/arm/include/asm/hardirq.h index 3d7351c844aa..fe3ea776dc34 100644 --- a/arch/arm/include/asm/hardirq.h +++ b/arch/arm/include/asm/hardirq.h @@ -5,7 +5,7 @@ #include <linux/threads.h> #include <asm/irq.h> -#define NR_IPI 7 +#define NR_IPI 8 typedef struct { unsigned int __softirq_pending; diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index b4048e370730..d021566d71c2 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -482,6 +482,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = { S(IPI_CPU_STOP, "CPU stop interrupts"), S(IPI_IRQ_WORK, "IRQ work interrupts"), S(IPI_COMPLETION, "completion interrupts"), + S(IPI_CPU_BACKTRACE, "CPU backtrace"), }; static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
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. To make the tracing work correctly, this extends the array by one entry and increases NR_IPI accordingly. This only works after patch e7273ff49acf ("ARM: 8488/1: Make IPI_CPU_BACKTRACE a "non-secure" SGI"), which changed the number assignment from '15' to '8'. If we decide to backport this patch to stable kernels, we probably need to backport e7273ff49acf as well. As far as I can tell, the problem has existed since the tracepoints were originally added, but it only triggered a gcc warning with the later change to NR_IPIS. 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 --- arch/arm/include/asm/hardirq.h | 2 +- arch/arm/kernel/smp.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) -- 2.7.0