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

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Message-Id: <200701301217.47520.bjorn.helgaas@hp.com>
Date:	Tue, 30 Jan 2007 12:17:47 -0700
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Frédéric Riss <frederic.riss@...il.com>
Cc:	linux-kernel@...r.kernel.org, artiom.myaskouvskey@...el.com,
	akpm@...l.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] EFI x86: pass firmware call parameters on the stack

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
> 
> 
> 
-
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