[PATCH 0/2] xen: Silence compiler warnings

[PATCH 0/2] xen: Silence compiler warnings

[Daniel Kiper]

Hi,

Here are two patches that follow earlier Xen dom0 EFI series and
fix some compiler warnings found during detailed build tests.

Both patches should be applied to:

git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git next

Daniel

PS I will be on vacation from 14th Jul till 25th Jul.

 arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
 include/xen/xen-ops.h    |    2 +-
 2 files changed, 23 insertions(+), 14 deletions(-)

Daniel Kiper (2):
      xen: Silence compiler warnings
      arch/x86/xen: Silence compiler warnings

[PATCH 1/2] xen: Silence compiler warnings

[Daniel Kiper]

Add inline keyword to silence the following compiler
warnings if xen_efi_probe() is not used:

  CC      arch/x86/xen/setup.o
In file included from arch/x86/xen/xen-ops.h:7:0,
                 from arch/x86/xen/setup.c:31:
include/xen/xen-ops.h:43:35: warning: ‘xen_efi_probe’ defined but not used [-Wunused-function]

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 include/xen/xen-ops.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 771bbba..7491ee5 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -40,7 +40,7 @@ bool xen_running_on_version_or_later(unsigned int major, unsigned int minor);
 #ifdef CONFIG_XEN_EFI
 extern efi_system_table_t *xen_efi_probe(void);
 #else
-static efi_system_table_t __init *xen_efi_probe(void)
+static inline efi_system_table_t __init *xen_efi_probe(void)
 {
 	return NULL;
 }
-- 
1.7.10.4

[PATCH 2/2] arch/x86/xen: Silence compiler warnings

[Daniel Kiper]

Compiler complains in the following way when x86 32-bit kernel
with Xen support is build:

  CC      arch/x86/xen/enlighten.o
arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]

Such line contains following EFI initialization code:

boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);

There is no issue if x86 64-bit kernel is build. However, 32-bit case
generate warning (even if that code will not be executed because Xen
does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
type which has 32-bits width. So move whole EFI initialization stuff
to separate function and build its body conditionally to avoid above
mentioned warning on x86 32-bit architecture.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bc89647..6abec74 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
 #endif
 }
 
+static void __init xen_efi_init(void)
+{
+#ifdef CONFIG_XEN_EFI
+	efi_system_table_t *efi_systab_xen;
+
+	efi_systab_xen = xen_efi_probe();
+
+	if (efi_systab_xen == NULL)
+		return;
+
+	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
+			sizeof(boot_params.efi_info.efi_loader_signature));
+	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
+	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
+
+	set_bit(EFI_BOOT, &efi.flags);
+	set_bit(EFI_PARAVIRT, &efi.flags);
+	set_bit(EFI_64BIT, &efi.flags);
+#endif
+}
+
 /* First C function to be called on Xen boot */
 asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	int rc;
-	efi_system_table_t *efi_systab_xen;
 
 	if (!xen_start_info)
 		return;
@@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	xen_setup_runstate_info(0);
 
-	efi_systab_xen = xen_efi_probe();
-
-	if (efi_systab_xen) {
-		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
-				sizeof(boot_params.efi_info.efi_loader_signature));
-		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
-		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
-
-		set_bit(EFI_BOOT, &efi.flags);
-		set_bit(EFI_PARAVIRT, &efi.flags);
-		set_bit(EFI_64BIT, &efi.flags);
-	}
+	xen_efi_init();
 
 	/* Start the world */
 #ifdef CONFIG_X86_32
-- 
1.7.10.4

Re: [PATCH 2/2] arch/x86/xen: Silence compiler warnings

[Boris Ostrovsky]

On 07/11/2014 03:54 PM, Daniel Kiper wrote:
> Compiler complains in the following way when x86 32-bit kernel
> with Xen support is build:
>
>    CC      arch/x86/xen/enlighten.o
> arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
> arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]
>
> Such line contains following EFI initialization code:
>
> boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
>
> There is no issue if x86 64-bit kernel is build. However, 32-bit case
> generate warning (even if that code will not be executed because Xen
> does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
> type which has 32-bits width. So move whole EFI initialization stuff
> to separate function and build its body conditionally to avoid above
> mentioned warning on x86 32-bit architecture.
>
> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
>   arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
>   1 file changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index bc89647..6abec74 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
>   #endif
>   }
>   
> +static void __init xen_efi_init(void)
> +{
> +#ifdef CONFIG_XEN_EFI
> +	efi_system_table_t *efi_systab_xen;
> +
> +	efi_systab_xen = xen_efi_probe();
> +
> +	if (efi_systab_xen == NULL)
> +		return;
> +
> +	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> +			sizeof(boot_params.efi_info.efi_loader_signature));
> +	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> +	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> +
> +	set_bit(EFI_BOOT, &efi.flags);
> +	set_bit(EFI_PARAVIRT, &efi.flags);
> +	set_bit(EFI_64BIT, &efi.flags);
> +#endif
> +}
> +
>   /* First C function to be called on Xen boot */
>   asmlinkage __visible void __init xen_start_kernel(void)
>   {
>   	struct physdev_set_iopl set_iopl;
>   	int rc;
> -	efi_system_table_t *efi_systab_xen;
>   
>   	if (!xen_start_info)
>   		return;
> @@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>   
>   	xen_setup_runstate_info(0);
>   
> -	efi_systab_xen = xen_efi_probe();
> -
> -	if (efi_systab_xen) {
> -		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> -				sizeof(boot_params.efi_info.efi_loader_signature));
> -		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> -		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> -
> -		set_bit(EFI_BOOT, &efi.flags);
> -		set_bit(EFI_PARAVIRT, &efi.flags);
> -		set_bit(EFI_64BIT, &efi.flags);
> -	}
> +	xen_efi_init();

I'd put ifdef CONFIG_XEN_EFI around the call instead of having it inside 
the routine.

-boris

>   
>   	/* Start the world */
>   #ifdef CONFIG_X86_32

Re: [PATCH 2/2] arch/x86/xen: Silence compiler warnings

[Daniel Kiper]

On Fri, Jul 11, 2014 at 04:03:46PM -0400, Boris Ostrovsky wrote:
> On 07/11/2014 03:54 PM, Daniel Kiper wrote:
> >Compiler complains in the following way when x86 32-bit kernel
> >with Xen support is build:
> >
> >   CC      arch/x86/xen/enlighten.o
> >arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
> >arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]
> >
> >Such line contains following EFI initialization code:
> >
> >boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >
> >There is no issue if x86 64-bit kernel is build. However, 32-bit case
> >generate warning (even if that code will not be executed because Xen
> >does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
> >type which has 32-bits width. So move whole EFI initialization stuff
> >to separate function and build its body conditionally to avoid above
> >mentioned warning on x86 32-bit architecture.
> >
> >Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> >---
> >  arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
> >  1 file changed, 22 insertions(+), 13 deletions(-)
> >
> >diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> >index bc89647..6abec74 100644
> >--- a/arch/x86/xen/enlighten.c
> >+++ b/arch/x86/xen/enlighten.c
> >@@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
> >  #endif
> >  }
> >+static void __init xen_efi_init(void)
> >+{
> >+#ifdef CONFIG_XEN_EFI
> >+	efi_system_table_t *efi_systab_xen;
> >+
> >+	efi_systab_xen = xen_efi_probe();
> >+
> >+	if (efi_systab_xen == NULL)
> >+		return;
> >+
> >+	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> >+			sizeof(boot_params.efi_info.efi_loader_signature));
> >+	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> >+	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >+
> >+	set_bit(EFI_BOOT, &efi.flags);
> >+	set_bit(EFI_PARAVIRT, &efi.flags);
> >+	set_bit(EFI_64BIT, &efi.flags);
> >+#endif
> >+}
> >+
> >  /* First C function to be called on Xen boot */
> >  asmlinkage __visible void __init xen_start_kernel(void)
> >  {
> >  	struct physdev_set_iopl set_iopl;
> >  	int rc;
> >-	efi_system_table_t *efi_systab_xen;
> >  	if (!xen_start_info)
> >  		return;
> >@@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
> >  	xen_setup_runstate_info(0);
> >-	efi_systab_xen = xen_efi_probe();
> >-
> >-	if (efi_systab_xen) {
> >-		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> >-				sizeof(boot_params.efi_info.efi_loader_signature));
> >-		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> >-		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >-
> >-		set_bit(EFI_BOOT, &efi.flags);
> >-		set_bit(EFI_PARAVIRT, &efi.flags);
> >-		set_bit(EFI_64BIT, &efi.flags);
> >-	}
> >+	xen_efi_init();
>
> I'd put ifdef CONFIG_XEN_EFI around the call instead of having it
> inside the routine.

Well, I thought about that a bit and I prefer function like Konrad.
Could you agree with him which solution do you (as maintainers) prefer?

Daniel

Re: [PATCH 2/2] arch/x86/xen: Silence compiler warnings

[Boris Ostrovsky]

On 07/11/2014 04:10 PM, Daniel Kiper wrote:
> On Fri, Jul 11, 2014 at 04:03:46PM -0400, Boris Ostrovsky wrote:
>> On 07/11/2014 03:54 PM, Daniel Kiper wrote:
>>> Compiler complains in the following way when x86 32-bit kernel
>>> with Xen support is build:
>>>
>>>    CC      arch/x86/xen/enlighten.o
>>> arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
>>> arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]
>>>
>>> Such line contains following EFI initialization code:
>>>
>>> boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
>>>
>>> There is no issue if x86 64-bit kernel is build. However, 32-bit case
>>> generate warning (even if that code will not be executed because Xen
>>> does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
>>> type which has 32-bits width. So move whole EFI initialization stuff
>>> to separate function and build its body conditionally to avoid above
>>> mentioned warning on x86 32-bit architecture.
>>>
>>> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
>>> ---
>>>   arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
>>>   1 file changed, 22 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
>>> index bc89647..6abec74 100644
>>> --- a/arch/x86/xen/enlighten.c
>>> +++ b/arch/x86/xen/enlighten.c
>>> @@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
>>>   #endif
>>>   }
>>> +static void __init xen_efi_init(void)
>>> +{
>>> +#ifdef CONFIG_XEN_EFI
>>> +	efi_system_table_t *efi_systab_xen;
>>> +
>>> +	efi_systab_xen = xen_efi_probe();
>>> +
>>> +	if (efi_systab_xen == NULL)
>>> +		return;
>>> +
>>> +	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
>>> +			sizeof(boot_params.efi_info.efi_loader_signature));
>>> +	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
>>> +	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
>>> +
>>> +	set_bit(EFI_BOOT, &efi.flags);
>>> +	set_bit(EFI_PARAVIRT, &efi.flags);
>>> +	set_bit(EFI_64BIT, &efi.flags);
>>> +#endif
>>> +}
>>> +
>>>   /* First C function to be called on Xen boot */
>>>   asmlinkage __visible void __init xen_start_kernel(void)
>>>   {
>>>   	struct physdev_set_iopl set_iopl;
>>>   	int rc;
>>> -	efi_system_table_t *efi_systab_xen;
>>>   	if (!xen_start_info)
>>>   		return;
>>> @@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>>>   	xen_setup_runstate_info(0);
>>> -	efi_systab_xen = xen_efi_probe();
>>> -
>>> -	if (efi_systab_xen) {
>>> -		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
>>> -				sizeof(boot_params.efi_info.efi_loader_signature));
>>> -		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
>>> -		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
>>> -
>>> -		set_bit(EFI_BOOT, &efi.flags);
>>> -		set_bit(EFI_PARAVIRT, &efi.flags);
>>> -		set_bit(EFI_64BIT, &efi.flags);
>>> -	}
>>> +	xen_efi_init();
>> I'd put ifdef CONFIG_XEN_EFI around the call instead of having it
>> inside the routine.
> Well, I thought about that a bit and I prefer function like Konrad.
> Could you agree with him which solution do you (as maintainers) prefer?
>

I am not arguing against having a separate routine. All I am saying is 
that calling xen_efi_init() when CONFIG_XEN_EFI is not defined doesn't 
look logical. It will also add an unnecessary call (although compiler 
may optimize it out).

-boris

Re: [PATCH 2/2] arch/x86/xen: Silence compiler warnings

[Daniel Kiper]

On Fri, Jul 11, 2014 at 04:32:27PM -0400, Boris Ostrovsky wrote:
> On 07/11/2014 04:10 PM, Daniel Kiper wrote:
> >On Fri, Jul 11, 2014 at 04:03:46PM -0400, Boris Ostrovsky wrote:
> >>On 07/11/2014 03:54 PM, Daniel Kiper wrote:
> >>>Compiler complains in the following way when x86 32-bit kernel
> >>>with Xen support is build:
> >>>
> >>>   CC      arch/x86/xen/enlighten.o
> >>>arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
> >>>arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]
> >>>
> >>>Such line contains following EFI initialization code:
> >>>
> >>>boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >>>
> >>>There is no issue if x86 64-bit kernel is build. However, 32-bit case
> >>>generate warning (even if that code will not be executed because Xen
> >>>does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
> >>>type which has 32-bits width. So move whole EFI initialization stuff
> >>>to separate function and build its body conditionally to avoid above
> >>>mentioned warning on x86 32-bit architecture.
> >>>
> >>>Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> >>>---
> >>>  arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
> >>>  1 file changed, 22 insertions(+), 13 deletions(-)
> >>>
> >>>diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> >>>index bc89647..6abec74 100644
> >>>--- a/arch/x86/xen/enlighten.c
> >>>+++ b/arch/x86/xen/enlighten.c
> >>>@@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
> >>>  #endif
> >>>  }
> >>>+static void __init xen_efi_init(void)
> >>>+{
> >>>+#ifdef CONFIG_XEN_EFI
> >>>+	efi_system_table_t *efi_systab_xen;
> >>>+
> >>>+	efi_systab_xen = xen_efi_probe();
> >>>+
> >>>+	if (efi_systab_xen == NULL)
> >>>+		return;
> >>>+
> >>>+	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> >>>+			sizeof(boot_params.efi_info.efi_loader_signature));
> >>>+	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> >>>+	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >>>+
> >>>+	set_bit(EFI_BOOT, &efi.flags);
> >>>+	set_bit(EFI_PARAVIRT, &efi.flags);
> >>>+	set_bit(EFI_64BIT, &efi.flags);
> >>>+#endif
> >>>+}
> >>>+
> >>>  /* First C function to be called on Xen boot */
> >>>  asmlinkage __visible void __init xen_start_kernel(void)
> >>>  {
> >>>  	struct physdev_set_iopl set_iopl;
> >>>  	int rc;
> >>>-	efi_system_table_t *efi_systab_xen;
> >>>  	if (!xen_start_info)
> >>>  		return;
> >>>@@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
> >>>  	xen_setup_runstate_info(0);
> >>>-	efi_systab_xen = xen_efi_probe();
> >>>-
> >>>-	if (efi_systab_xen) {
> >>>-		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
> >>>-				sizeof(boot_params.efi_info.efi_loader_signature));
> >>>-		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
> >>>-		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
> >>>-
> >>>-		set_bit(EFI_BOOT, &efi.flags);
> >>>-		set_bit(EFI_PARAVIRT, &efi.flags);
> >>>-		set_bit(EFI_64BIT, &efi.flags);
> >>>-	}
> >>>+	xen_efi_init();
> >>I'd put ifdef CONFIG_XEN_EFI around the call instead of having it
> >>inside the routine.
> >Well, I thought about that a bit and I prefer function like Konrad.
> >Could you agree with him which solution do you (as maintainers) prefer?
> >
>
> I am not arguing against having a separate routine. All I am saying
> is that calling xen_efi_init() when CONFIG_XEN_EFI is not defined
> doesn't look logical. It will also add an unnecessary call (although

Ahh... I misunderstood you. However, your proposal, as below:

#ifdef CONFIG_XEN_EFI
  xen_efi_init();
#endif

does not solve the problem because this vulnerable shift will be still
visible for compiler during x86 32-bit kernel build.

> compiler may optimize it out).

Please loot at arch/x86/xen/enlighten.c:xen_check_mwait() and
arch/x86/xen/enlighten.c:xen_boot_params_init_edd() (probably
there are more stuff like that around). As I can see this is fairly
common solution and probably compiler cope with it quite well.

Have a nice weekend,

Daniel