Re: [PATCH 3/5] x86/boot: Remove hardcoded boot_param constants

[Brian Gerst]

On Fri, Jul 24, 2026 at 2:22 PM Tom Lendacky <thomas.lendacky@xxxxxxx> wrote:
>
> On 7/23/26 22:02, Brian Gerst wrote:
> > Use generated constants or sizeof() instead of hardcoded values.
> >
> > No functional change.
> >
> > Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
> > ---
> >  arch/x86/include/asm/setup.h            | 3 ---
> >  arch/x86/kernel/asm-offsets.c           | 2 ++
> >  arch/x86/kernel/head_32.S               | 4 ++--
> >  drivers/firmware/efi/libstub/x86-stub.c | 6 +++---
> >  4 files changed, 7 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
> > index 5534f4aaf73b..d23f4272d930 100644
> > --- a/arch/x86/include/asm/setup.h
> > +++ b/arch/x86/include/asm/setup.h
> > @@ -21,11 +21,8 @@
> >
> >  #endif /* __i386__ */
> >
> > -#define PARAM_SIZE 4096              /* sizeof(struct boot_params) */
> > -
> >  #define OLD_CL_MAGIC         0xA33F
> >  #define OLD_CL_ADDRESS               0x020   /* Relative to real mode data */
> > -#define NEW_CL_POINTER               0x228   /* Relative to real mode data */
> >
> >  #ifndef __ASSEMBLER__
> >  #include <linux/cache.h>
> > diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
> > index 081816888f7a..0c49bb50188d 100644
> > --- a/arch/x86/kernel/asm-offsets.c
> > +++ b/arch/x86/kernel/asm-offsets.c
> > @@ -105,6 +105,8 @@ static void __used common(void)
> >       OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
> >       OFFSET(BP_init_size, boot_params, hdr.init_size);
> >       OFFSET(BP_pref_address, boot_params, hdr.pref_address);
> > +     OFFSET(BP_cmd_line_ptr, boot_params, hdr.cmd_line_ptr);
> > +     DEFINE(SIZEOF_boot_params, sizeof(struct boot_params));
> >
> >       BLANK();
> >       DEFINE(PTREGS_SIZE, sizeof(struct pt_regs));
> > diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
> > index 5171cb746444..1f66ccc36fe8 100644
> > --- a/arch/x86/kernel/head_32.S
> > +++ b/arch/x86/kernel/head_32.S
> > @@ -96,10 +96,10 @@ SYM_CODE_START(startup_32)
> >   * page tables.
> >   */
> >       movl $pa(boot_params),%edi
> > -     movl $(PARAM_SIZE/4),%ecx
> > +     movl $(SIZEOF_boot_params/4),%ecx
> >       cld
> >       rep movsl
> > -     movl pa(boot_params) + NEW_CL_POINTER,%esi
> > +     movl pa(boot_params) + BP_cmd_line_ptr,%esi
> >       andl %esi,%esi
> >       jz 1f                   # No command line
> >       movl $pa(boot_command_line),%edi
> > diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
> > index cef32e2c82d8..c3522d417344 100644
> > --- a/drivers/firmware/efi/libstub/x86-stub.c
> > +++ b/drivers/firmware/efi/libstub/x86-stub.c
> > @@ -520,11 +520,11 @@ static efi_status_t efi_allocate_bootparams(efi_handle_t handle,
> >               return status;
> >       }
> >
> > -     status = efi_allocate_pages(PARAM_SIZE, &alloc, ULONG_MAX);
> > +     status = efi_allocate_pages(sizeof(struct boot_params), &alloc, ULONG_MAX);
>
> Why not sizeof(*boot_params) here and each place below instead of
> hardcoding the struct?

Will change for v2.