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

[Dave Martin <Dave.Martin@arm.com>]

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.)

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

>  
>  /*
>   * 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