linux-kernel - Re: [PATCH v14 1/3] /proc/pid/status: Add support for architecture specific output

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Date:   Wed, 10 Apr 2019 11:39:58 +0800
From:   "Li, Aubrey" <aubrey.li@...ux.intel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, aubrey.li@...el.com,
        Linux API <linux-api@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 1/3] /proc/pid/status: Add support for architecture
 specific output

On 2019/4/10 10:36, Li, Aubrey wrote:
> On 2019/4/10 10:25, Andy Lutomirski wrote:
>> On Tue, Apr 9, 2019 at 7:20 PM Li, Aubrey <aubrey.li@...ux.intel.com> wrote:
>>>
>>> On 2019/4/10 9:58, Andy Lutomirski wrote:
>>>> On Tue, Apr 9, 2019 at 6:55 PM Aubrey Li <aubrey.li@...ux.intel.com> wrote:
>>>>>
>>>>> The architecture specific information of the running processes could
>>>>> be useful to the userland. Add support to examine process architecture
>>>>> specific information externally.
>>>>>
>>>>> Signed-off-by: Aubrey Li <aubrey.li@...ux.intel.com>
>>>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>>>> Cc: Andi Kleen <ak@...ux.intel.com>
>>>>> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
>>>>> Cc: Dave Hansen <dave.hansen@...el.com>
>>>>> Cc: Arjan van de Ven <arjan@...ux.intel.com>
>>>>> Cc: Linux API <linux-api@...r.kernel.org>
>>>>> Cc: Alexey Dobriyan <adobriyan@...il.com>
>>>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>>>> ---
>>>>>  fs/proc/array.c         | 5 +++++
>>>>>  include/linux/proc_fs.h | 2 ++
>>>>>  2 files changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/fs/proc/array.c b/fs/proc/array.c
>>>>> index 2edbb657f859..331592a61718 100644
>>>>> --- a/fs/proc/array.c
>>>>> +++ b/fs/proc/array.c
>>>>> @@ -401,6 +401,10 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
>>>>>         seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
>>>>>  }
>>>>>
>>>>> +void __weak arch_proc_pid_status(struct seq_file *m, struct task_struct *task)
>>>>> +{
>>>>> +}
>>>>
>>>> This pointlessly bloats other architectures.  Do this instead in an
>>>> appropriate header:
>>>>
>>>> #ifndef arch_proc_pid_status
>>>> static inline void arch_proc_pid_status(...)
>>>> {
>>>> }
>>>> #endif
>>>>
>>>
>>> I saw a bunch of similar weak functions, is it not acceptable?
>>>
>>> fs/proc$ grep weak *.c
>>> cpuinfo.c:__weak void arch_freq_prepare_all(void)
>>> meminfo.c:void __attribute__((weak)) arch_report_meminfo(struct seq_file *m)
>>> vmcore.c:int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
>>> vmcore.c:void __weak elfcorehdr_free(unsigned long long addr)
>>> vmcore.c:ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>>> vmcore.c:ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
>>> vmcore.c:int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
>>> vmcore.c:ssize_t __weak
>>
>> I think they're acceptable, but I don't personally like them.
>>
> 
> okay, let me try to see if I can refine it in an appropriate way.

Hi Andy,

Is this what you want? 

Thanks,
-Aubrey

====================================================================
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 2bb3a648fc12..82d77d3aefff 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -990,5 +990,8 @@ enum l1tf_mitigations {
 };
 
 extern enum l1tf_mitigations l1tf_mitigation;
+/* Add support for architecture specific output in /proc/pid/status */
+void arch_proc_pid_status(struct seq_file *m, struct task_struct *task);
+#define arch_proc_pid_status arch_proc_pid_status
 
 #endif /* _ASM_X86_PROCESSOR_H */
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 2edbb657f859..fd65a6ba2864 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -401,6 +401,11 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
 	seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
 }
 
+/* Add support for architecture specific output in /proc/pid/status */
+#ifndef arch_proc_pid_status
+#define arch_proc_pid_status(m, task)
+#endif
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)
 {
@@ -424,6 +429,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 	task_cpus_allowed(m, task);
 	cpuset_task_status_allowed(m, task);
 	task_context_switch_counts(m, task);
+	arch_proc_pid_status(m, task);
 	return 0;
 }