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

Dave Martin
2025-01-07T16:17:55Z

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