Re: [PATCH v3 5/6] s390/crash: Use note name macros

Akihiko Odaki
2025-01-08T04:54:00Z

On 2025/01/08 1:17, Dave Martin wrote:
> Hi,
>
> On Tue, Jan 07, 2025 at 09:45:56PM +0900, Akihiko Odaki wrote:
>> Use note name macros to match with the userspace's expectation.
>>
>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>> ---
>> arch/s390/kernel/crash_dump.c | 62 ++++++++++++++++---------------------------
>> 1 file changed, 23 insertions(+), 39 deletions(-)
>>
>> diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
>
> [...]
>
>> @@ -281,10 +272,8 @@ static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len,
>> return PTR_ADD(buf, len);
>> }
>>
>> -static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len)
>> -{
>> - return nt_init_name(buf, type, desc, d_len, nt_name(type));
>> -}
>> +#define NT_INIT(buf, type, desc) \
>> + (nt_init_name((buf), NT_ ## type, &(desc), sizeof(desc), NN_ ## type))
>
> Nit: this macro name clashes with the naming scheme in elf.h.
>
> I think that there is a (weak) convention that macros with upper-case
> names don't expand to a C function call; thus, a macro with an upper-
> case name can be invoked in places where a C function call would not be
> allowed. (This convention is not followed everywhere, though -- it's
> up to the maintainer what they prefer here.)

I wanted to clarify it is a macro as it concatenates tokens with ##, but
I also find there are many macros that are named lower-case and performs
token concatenation.

S390 maintainers, please tell usr your opinion.

>
> (Note also, the outer parentheses and the parentheses around (buf)
> appear redundant -- although harmless?)

They only make a difference in trivial corner cases and may look
needlessly verbose.

>
>>
>> /*
>> * Calculate the size of ELF note
>> @@ -300,10 +289,7 @@ static size_t nt_size_name(int d_len, const char *name)
>> return size;
>> }
>>
>> -static inline size_t nt_size(Elf64_Word type, int d_len)
>> -{
>> - return nt_size_name(d_len, nt_name(type));
>> -}
>> +#define NT_SIZE(type, desc) (nt_size_name(sizeof(desc), NN_ ## type))
>
> Nit: name prefix clash (again); possibly redundant parentheses.
>
> [...]
>
>> @@ -348,16 +332,16 @@ static size_t get_cpu_elf_notes_size(void)
>> struct save_area *sa = NULL;
>> size_t size;
>>
>> - size = nt_size(NT_PRSTATUS, sizeof(struct elf_prstatus));
>> - size += nt_size(NT_PRFPREG, sizeof(elf_fpregset_t));
>> - size += nt_size(NT_S390_TIMER, sizeof(sa->timer));
>> - size += nt_size(NT_S390_TODCMP, sizeof(sa->todcmp));
>> - size += nt_size(NT_S390_TODPREG, sizeof(sa->todpreg));
>> - size += nt_size(NT_S390_CTRS, sizeof(sa->ctrs));
>> - size += nt_size(NT_S390_PREFIX, sizeof(sa->prefix));
>> + size = NT_SIZE(PRSTATUS, struct elf_prstatus);
>> + size += NT_SIZE(PRFPREG, elf_fpregset_t);
>> + size += NT_SIZE(S390_TIMER, sa->timer);
>> + size += NT_SIZE(S390_TODCMP, sa->todcmp);
>> + size += NT_SIZE(S390_TODPREG, sa->todpreg);
>> + size += NT_SIZE(S390_CTRS, sa->ctrs);
>> + size += NT_SIZE(S390_PREFIX, sa->prefix);
>
> It might be worth fixing the funny spacing on these lines, since all
> the affected lines are being replaced.
>
>> if (cpu_has_vx()) {
>> - size += nt_size(NT_S390_VXRS_HIGH, sizeof(sa->vxrs_high));
>> - size += nt_size(NT_S390_VXRS_LOW, sizeof(sa->vxrs_low));
>> + size += NT_SIZE(S390_VXRS_HIGH, sa->vxrs_high);
>> + size += NT_SIZE(S390_VXRS_LOW, sa->vxrs_low);
>> }
>>
>> return size;
>> @@ -373,7 +357,7 @@ static void *nt_prpsinfo(void *ptr)
>> memset(&prpsinfo, 0, sizeof(prpsinfo));
>> prpsinfo.pr_sname = 'R';
>> strcpy(prpsinfo.pr_fname, "vmlinux");
>> - return nt_init(ptr, NT_PRPSINFO, &prpsinfo, sizeof(prpsinfo));
>> + return NT_INIT(ptr, PRPSINFO, prpsinfo);
>> }
>>
>> /*
>> @@ -589,7 +573,7 @@ static size_t get_elfcorehdr_size(int phdr_count)
>> /* PT_NOTES */
>> size += sizeof(Elf64_Phdr);
>> /* nt_prpsinfo */
>> - size += nt_size(NT_PRPSINFO, sizeof(struct elf_prpsinfo));
>> + size += NT_SIZE(PRPSINFO, struct elf_prpsinfo);
>> /* regsets */
>> size += get_cpu_cnt() * get_cpu_elf_notes_size();
>> /* nt_vmcoreinfo */
>
> Otherwise, this looks sensible to me.
>
> Cheers
> ---Dave