https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84095
--- Comment #14 from Arnd Bergmann <arnd at linaro dot org> ---
I applied the patches and seem to still get a warning for this:
$ x86_64-linux-gcc-8.0.1 -Wall -O2 -c nmi_int.c
nmi_int.c: In function 'nmi_setup':
nmi_int.c:43:3: warning: 'memcpy' source argument is the same as destination
[-Wrestrict]
memcpy(per_cpu(cpu_msrs, cpu).counters,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
per_cpu(cpu_msrs, 0).counters,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sizeof(int) * model->num_counters);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
typedef unsigned long __kernel_size_t;
extern void * memcpy(void *,const void *,__kernel_size_t);
struct op_msrs {
int *counters;
};
#define for_each_possible_cpu(cpu) for_each_cpu((cpu), cpu_possible_mask)
#define for_each_cpu(cpu, mask) for ((cpu) = 0; (cpu) < 1; (cpu)++,(void)mask)
extern struct cpumask __cpu_possible_mask;
#define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask)
#define DEFINE_PER_CPU(type, name) __typeof__(type) name
#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); ptr; })
#define raw_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
#define per_cpu(var, cpu) (*per_cpu_ptr(&(var), cpu))
extern void *pcpu_base_addr;
extern const unsigned long *pcpu_unit_offsets;
struct op_x86_model_spec {
unsigned int num_counters;
};
static struct op_x86_model_spec *model;
static DEFINE_PER_CPU(struct op_msrs, cpu_msrs);
int nmi_setup(void)
{
int err = 0;
int cpu;
for_each_possible_cpu(cpu) {
if (!cpu)
continue;
memcpy(per_cpu(cpu_msrs, cpu).counters,
per_cpu(cpu_msrs, 0).counters,
sizeof(int) * model->num_counters);
}
return err;
}
In this code, we do copy from a variable onto itself, but only in a dead
branch, here because the for_each_possible_cpu() and per_cpu() macros degrade
to trivial wrappers on an non-SMP build.
