Re: [RFC V2 2/8] powerpc: Prepare to build with generic entry/exit framework

Shrikanth Hegde
2025-09-13T12:50:20Z

On 9/9/25 2:32 AM, Mukesh Kumar Chaurasiya wrote:
> Enabling build with generic entry/exit framework for powerpc
> architecture requires few necessary steps.
>
> Introducing minor infrastructure updates to prepare for future generic
> framework handling:
>
> - Add syscall_work field to struct thread_info for SYSCALL_WORK_* flags.
> - Provide arch_syscall_is_vdso_sigreturn() stub, returning false.
> - Add on_thread_stack() helper to test whether the current stack pointer
> lies within the task’s kernel stack.
>
> No functional change is intended with this patch.
>
> Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
> ---
> arch/powerpc/include/asm/entry-common.h | 11 +++++++++++
> arch/powerpc/include/asm/stacktrace.h | 8 ++++++++
> arch/powerpc/include/asm/syscall.h | 5 +++++
> arch/powerpc/include/asm/thread_info.h | 1 +
> 4 files changed, 25 insertions(+)
> create mode 100644 arch/powerpc/include/asm/entry-common.h
>
> diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
> new file mode 100644
> index 0000000000000..3af16d821d07e
> --- /dev/null
> +++ b/arch/powerpc/include/asm/entry-common.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _ASM_PPC_ENTRY_COMMON_H
> +#define _ASM_PPC_ENTRY_COMMON_H
> +
> +#ifdef CONFIG_GENERIC_IRQ_ENTRY
> +
> +#include <asm/stacktrace.h>
> +
> +#endif /* CONFIG_GENERIC_IRQ_ENTRY */
> +#endif /* _ASM_PPC_ENTRY_COMMON_H */
> diff --git a/arch/powerpc/include/asm/stacktrace.h b/arch/powerpc/include/asm/stacktrace.h
> index 6149b53b3bc8e..3f0a242468813 100644
> --- a/arch/powerpc/include/asm/stacktrace.h
> +++ b/arch/powerpc/include/asm/stacktrace.h
> @@ -8,6 +8,14 @@
> #ifndef _ASM_POWERPC_STACKTRACE_H
> #define _ASM_POWERPC_STACKTRACE_H
>
> +#include <linux/sched.h>

nit:

Is sched.h needed? I don't see any reference here.
It compiled for me without it.

> +
> void show_user_instructions(struct pt_regs *regs);
>
> +static inline bool on_thread_stack(void)
> +{
> + return !(((unsigned long)(current->stack) ^ current_stack_pointer)
> + & ~(THREAD_SIZE -1));
> +}
> +
> #endif /* _ASM_POWERPC_STACKTRACE_H */
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 4b3c52ed6e9d2..834fcc4f7b543 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -139,4 +139,9 @@ static inline int syscall_get_arch(struct task_struct *task)
> else
> return AUDIT_ARCH_PPC64;
> }
> +
> +static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
> +{
> + return false;
> +}
> #endif /* _ASM_SYSCALL_H */
> diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> index 2785c7462ebf7..d0e87c9bae0b0 100644
> --- a/arch/powerpc/include/asm/thread_info.h
> +++ b/arch/powerpc/include/asm/thread_info.h
> @@ -54,6 +54,7 @@
> struct thread_info {
> int preempt_count; /* 0 => preemptable,
> <0 => BUG */
> + unsigned long syscall_work; /* SYSCALL_WORK_ flags */

Can this go after cpu ? it would be 8 byte aligned then. Since it is in
fast path, might help.

> #ifdef CONFIG_SMP
> unsigned int cpu;
> #endif