Re: [PATCH] EFI x86: pass firmware call parameters on the stack

Bjorn Helgaas
2007-01-30T19:18:04Z

On Tuesday 30 January 2007 12:01, Frédéric Riss wrote:
> When calling into an EFI firmware, the parameters need to be passed on
> the stack. The recent change to use -mregparm=3 breaks x86 EFI support.
> This patch is needed to allow the new Intel-based Macs to suspend to ram
> when run in EFI mode (efi.get_time is called during the suspend phase).
> ...
> This patch fixes the issue for x86, but the file is also used by IA64. I
> would have used asmlinkage to force arguments on the stack, but it has a
> special meaning on IA64, thus I used a raw regparm(0) GCC attribute.
> This attribute is documented only for x86, I hope it has no side effect
> on other archs.

It seems wrong to put this sort of architecture-dependent stuff in
an architecture-independent file. If EFI needs a specific calling
convention on x86, x86 should provide wrappers that guarantee that
convention. ia64 already provides such wrappers (phys_get_time(),
virt_get_time(), etc).

> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index df1c918..1db5321 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -157,25 +157,35 @@ typedef struct {
> unsigned long reset_system;
> } efi_runtime_services_t;
>
> -typedef efi_status_t efi_get_time_t (efi_time_t *tm, efi_time_cap_t *tc);
> -typedef efi_status_t efi_set_time_t (efi_time_t *tm);
> +typedef efi_status_t efi_get_time_t (efi_time_t *tm, efi_time_cap_t *tc)
> + __attribute__((regparm(0)));
> +typedef efi_status_t efi_set_time_t (efi_time_t *tm)
> + __attribute__((regparm(0)));
> typedef efi_status_t efi_get_wakeup_time_t (efi_bool_t *enabled, efi_bool_t *pending,
> - efi_time_t *tm);
> -typedef efi_status_t efi_set_wakeup_time_t (efi_bool_t enabled, efi_time_t *tm);
> + efi_time_t *tm)
> + __attribute__((regparm(0)));
> +typedef efi_status_t efi_set_wakeup_time_t (efi_bool_t enabled, efi_time_t *tm)
> + __attribute__((regparm(0)));
> typedef efi_status_t efi_get_variable_t (efi_char16_t *name, efi_guid_t *vendor, u32 *attr,
> - unsigned long *data_size, void *data);
> + unsigned long *data_size, void *data)
> + __attribute__((regparm(0)));
> typedef efi_status_t efi_get_next_variable_t (unsigned long *name_size, efi_char16_t *name,
> - efi_guid_t *vendor);
> + efi_guid_t *vendor)
> + __attribute__((regparm(0)));
> typedef efi_status_t efi_set_variable_t (efi_char16_t *name, efi_guid_t *vendor,
> unsigned long attr, unsigned long data_size,
> - void *data);
> -typedef efi_status_t efi_get_next_high_mono_count_t (u32 *count);
> + void *data)
> + __attribute__((regparm(0)));
> +typedef efi_status_t efi_get_next_high_mono_count_t (u32 *count)
> + __attribute__((regparm(0)));
> typedef void efi_reset_system_t (int reset_type, efi_status_t status,
> - unsigned long data_size, efi_char16_t *data);
> + unsigned long data_size, efi_char16_t *data)
> + __attribute__((regparm(0)));
> typedef efi_status_t efi_set_virtual_address_map_t (unsigned long memory_map_size,
> unsigned long descriptor_size,
> u32 descriptor_version,
> - efi_memory_desc_t *virtual_map);
> + efi_memory_desc_t *virtual_map)
> + __attribute__((regparm(0)));
>
> /*
> * EFI Configuration Table and GUID definitions
>
>
>