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

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Message-ID: <e7012ea8-5294-492c-94f8-fd2a81789d2f@linux.ibm.com>
Date: Tue, 16 Sep 2025 09:46:23 +0530
From: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>,
        Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, oleg@...hat.com, kees@...nel.org,
        luto@...capital.net, wad@...omium.org, deller@....de, ldv@...ace.io,
        macro@...am.me.uk, charlie@...osinc.com, akpm@...ux-foundation.org,
        bigeasy@...utronix.de, ankur.a.arora@...cle.com, naveen@...nel.org,
        thomas.weissschuh@...utronix.de, Jason@...c4.com, peterz@...radead.org,
        tglx@...utronix.de, namcao@...utronix.de, kan.liang@...ux.intel.com,
        mingo@...nel.org, oliver.upton@...ux.dev, mark.barnett@....com,
        atrajeev@...ux.vnet.ibm.com, rppt@...nel.org, coltonlewis@...gle.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC V2 2/8] powerpc: Prepare to build with generic entry/exit
 framework


On 9/13/25 6:19 PM, Shrikanth Hegde wrote:
>
>
> 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@...ux.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.
>
Will remove this in next revision.
>> +
>>   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.
>
Oh yeah, will move this in next revision.

Thanks,

Mukesh

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