| Message ID | 20210907220038.91021-5-keithpac@amazon.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/7] ARM: Pass cpu number to secondary_start_kernel | expand |
On Wed, 8 Sept 2021 at 00:00, Keith Packard <keithpac@amazon.com> wrote: > > When we enable THREAD_INFO_IN_TASK, the cpu number will disappear from > thread_info and reappear in task_struct. As we cannot include > linux/sched.h in asm/smp.h, there's no way to use that struct type in > the raw_smp_processor_id macro. Instead, a hack from the powerpc code > is used. This pulls the TI_CPU offset out of asm-offsets.h and uses > that to find the cpu value. > > Signed-off-by: Keith Packard <keithpac@amazon.com> > --- > arch/arm/Makefile | 8 ++++++++ > arch/arm/include/asm/smp.h | 18 +++++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index 415c3514573a..6752995d2914 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -284,6 +284,14 @@ stack_protector_prepare: prepare0 > $(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS)) > endif > > +ifdef CONFIG_SMP > +prepare: task_cpu_prepare > + > +PHONY += task_cpu_prepare > +task_cpu_prepare: prepare0 > + $(eval KBUILD_CFLAGS += -D_TI_CPU=$(shell awk '{if ($$2 == "TI_CPU") print $$3;}' include/generated/asm-offsets.h)) > +endif > + > all: $(notdir $(KBUILD_IMAGE)) > > > diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h > index d43b64635d77..f77ba3753bc4 100644 > --- a/arch/arm/include/asm/smp.h > +++ b/arch/arm/include/asm/smp.h > @@ -15,7 +15,23 @@ > # error "<asm/smp.h> included in non-SMP build" > #endif > > -#define raw_smp_processor_id() (current_thread_info()->cpu) > +/* > + * This is particularly ugly: it appears we can't actually get the > + * definition of task_struct here, but we need access to the CPU this > + * task is running on, which is stored in task_struct when > + * THREAD_INFO_IN_TASK is set. Instead of using task_struct we're > + * using TI_CPU which is extracted from asm-offsets.h by kbuild to get > + * the current processor ID. > + * > + * This also needs to be safeguarded when building asm-offsets.s > + * because at that time TI_CPU is not defined yet. > + */ > +#ifndef _TI_CPU > +#define raw_smp_processor_id() (0) > +#else > +#define raw_smp_processor_id() \ > + (*(unsigned int *)((void *)current_thread_info() + _TI_CPU)) > +#endif > > struct seq_file; > As I stated before, I would really like to avoid using this hack - I don't think we need to.
diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 415c3514573a..6752995d2914 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -284,6 +284,14 @@ stack_protector_prepare: prepare0 $(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS)) endif +ifdef CONFIG_SMP +prepare: task_cpu_prepare + +PHONY += task_cpu_prepare +task_cpu_prepare: prepare0 + $(eval KBUILD_CFLAGS += -D_TI_CPU=$(shell awk '{if ($$2 == "TI_CPU") print $$3;}' include/generated/asm-offsets.h)) +endif + all: $(notdir $(KBUILD_IMAGE)) diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h index d43b64635d77..f77ba3753bc4 100644 --- a/arch/arm/include/asm/smp.h +++ b/arch/arm/include/asm/smp.h @@ -15,7 +15,23 @@ # error "<asm/smp.h> included in non-SMP build" #endif -#define raw_smp_processor_id() (current_thread_info()->cpu) +/* + * This is particularly ugly: it appears we can't actually get the + * definition of task_struct here, but we need access to the CPU this + * task is running on, which is stored in task_struct when + * THREAD_INFO_IN_TASK is set. Instead of using task_struct we're + * using TI_CPU which is extracted from asm-offsets.h by kbuild to get + * the current processor ID. + * + * This also needs to be safeguarded when building asm-offsets.s + * because at that time TI_CPU is not defined yet. + */ +#ifndef _TI_CPU +#define raw_smp_processor_id() (0) +#else +#define raw_smp_processor_id() \ + (*(unsigned int *)((void *)current_thread_info() + _TI_CPU)) +#endif struct seq_file;
When we enable THREAD_INFO_IN_TASK, the cpu number will disappear from thread_info and reappear in task_struct. As we cannot include linux/sched.h in asm/smp.h, there's no way to use that struct type in the raw_smp_processor_id macro. Instead, a hack from the powerpc code is used. This pulls the TI_CPU offset out of asm-offsets.h and uses that to find the cpu value. Signed-off-by: Keith Packard <keithpac@amazon.com> --- arch/arm/Makefile | 8 ++++++++ arch/arm/include/asm/smp.h | 18 +++++++++++++++++- 2 files changed, 25 insertions(+), 1 deletion(-)