4.4.0-rc2 tagged

4.4.0-rc2 tagged

[Ian Campbell]

We've just tagged 4.4.0-rc2, please test and report bugs.

The tarball can be downloaded here:

http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz

Ian.

Re: 4.4.0-rc2 tagged

[Don Slutz]

On 01/14/14 11:29, Ian Campbell wrote:
> We've just tagged 4.4.0-rc2, please test and report bugs.
>
> The tarball can be downloaded here:
>
> http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz
>
> Ian.
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

This tarball does not build on CentOS 5.10:


gcc -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing -std=gnu99 
-Wall -Wstrict-prototypes -Wdeclaration-after-statement 
-I/home/don/xen-4.4.0-rc2/xen/include 
-I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-generic 
-I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-default -msoft-float 
-fno-stack-protector -fno-exceptions -Wnested-externs -DHAVE_GAS_VMX 
-mno-red-zone -mno-sse -fpic -fno-asynchronous-unwind-tables 
-DGCC_HAS_VISIBILITY_ATTRIBUTE -fno-builtin -fno-common -Werror 
-Wredundant-decls -Wno-pointer-arith -pipe -g -D__XEN__ -include 
/home/don/xen-4.4.0-rc2/xen/include/xen/config.h -nostdinc -iwithprefix 
include -fno-optimize-sibling-calls -DVERBOSE -DHAS_ACPI -DHAS_GDBSX 
-DHAS_PASSTHROUGH -DHAS_PCI -DHAS_IOPORTS -fno-omit-frame-pointer 
-DCONFIG_FRAME_POINTER -MMD -MF .memory.o.d -c memory.c -o memory.o
cc1: warnings being treated as errors
memory.c: In function 'compat_memory_op':
memory.c:213: warning: comparison is always true due to limited range of 
data type
memory.c:214: warning: comparison is always true due to limited range of 
data type
memory.c:215: warning: comparison is always true due to limited range of 
data type
make[5]: *** [memory.o] Error 1
make[5]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common/compat'
make[4]: *** [compat/built_in.o] Error 2
make[4]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common'
make[3]: *** [/home/don/xen-4.4.0-rc2/xen/common/built_in.o] Error 2
make[3]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/arch/x86'
make[2]: *** [/home/don/xen-4.4.0-rc2/xen/xen] Error 2
make[2]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
make[1]: *** [install] Error 2
make[1]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
make: *** [install-xen] Error 2
dcs-xen-53:~/xen-4.4.0-rc2>uname -a
Linux dcs-xen-53 2.6.18-371.el5xen #1 SMP Tue Oct 1 09:15:30 EDT 2013 
x86_64 x86_64 x86_64 GNU/Linux
dcs-xen-53:~/xen-4.4.0-rc2>cat /etc/redhat-release
CentOS release 5.10 (Final)
dcs-xen-53:~/xen-4.4.0-rc2>gcc -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
--infodir=/usr/share/info --enable-shared --enable-threads=posix 
--enable-checking=release --with-system-zlib --enable-__cxa_atexit 
--disable-libunwind-exceptions --enable-libgcj-multifile 
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada 
--enable-java-awt=gtk --disable-dssi --disable-plugin 
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre 
--with-cpu=generic --host=x86_64-redhat-linux
Thread model: posix
gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)


git blame points to:


dcs-xen-53:~/xen>git show 244ce6f4
commit 244ce6f42d1843c02be36ed808452df570378cb1
Author: Jan Beulich <jbeulich@suse.com>
Date:   Wed Jan 8 09:06:07 2014 +0100

     compat wrapper for XENMEM_add_to_physmap_batch

     Signed-off-by: Jan Beulich <jbeulich@suse.com>
     Acked-by: Keir Fraser <keir@xen.org>
...


     -Don Slutz

Re: 4.4.0-rc2 tagged

[Andrew Cooper]

On 14/01/2014 22:49, Don Slutz wrote:
> On 01/14/14 11:29, Ian Campbell wrote:
>> We've just tagged 4.4.0-rc2, please test and report bugs.
>>
>> The tarball can be downloaded here:
>>
>> http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz
>>
>> Ian.
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel
>
> This tarball does not build on CentOS 5.10:
>
>
> gcc -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing
> -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement
> -I/home/don/xen-4.4.0-rc2/xen/include
> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-generic
> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-default
> -msoft-float -fno-stack-protector -fno-exceptions -Wnested-externs
> -DHAVE_GAS_VMX -mno-red-zone -mno-sse -fpic
> -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE
> -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith
> -pipe -g -D__XEN__ -include
> /home/don/xen-4.4.0-rc2/xen/include/xen/config.h -nostdinc
> -iwithprefix include -fno-optimize-sibling-calls -DVERBOSE -DHAS_ACPI
> -DHAS_GDBSX -DHAS_PASSTHROUGH -DHAS_PCI -DHAS_IOPORTS
> -fno-omit-frame-pointer -DCONFIG_FRAME_POINTER -MMD -MF .memory.o.d -c
> memory.c -o memory.o
> cc1: warnings being treated as errors
> memory.c: In function 'compat_memory_op':
> memory.c:213: warning: comparison is always true due to limited range
> of data type
> memory.c:214: warning: comparison is always true due to limited range
> of data type
> memory.c:215: warning: comparison is always true due to limited range
> of data type
> make[5]: *** [memory.o] Error 1
> make[5]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common/compat'
> make[4]: *** [compat/built_in.o] Error 2
> make[4]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common'
> make[3]: *** [/home/don/xen-4.4.0-rc2/xen/common/built_in.o] Error 2
> make[3]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/arch/x86'
> make[2]: *** [/home/don/xen-4.4.0-rc2/xen/xen] Error 2
> make[2]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
> make[1]: *** [install] Error 2
> make[1]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
> make: *** [install-xen] Error 2
> dcs-xen-53:~/xen-4.4.0-rc2>uname -a
> Linux dcs-xen-53 2.6.18-371.el5xen #1 SMP Tue Oct 1 09:15:30 EDT 2013
> x86_64 x86_64 x86_64 GNU/Linux
> dcs-xen-53:~/xen-4.4.0-rc2>cat /etc/redhat-release
> CentOS release 5.10 (Final)
> dcs-xen-53:~/xen-4.4.0-rc2>gcc -v
> Using built-in specs.
> Target: x86_64-redhat-linux
> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
> --infodir=/usr/share/info --enable-shared --enable-threads=posix
> --enable-checking=release --with-system-zlib --enable-__cxa_atexit
> --disable-libunwind-exceptions --enable-libgcj-multifile
> --enable-languages=c,c++,objc,obj-c++,java,fortran,ada
> --enable-java-awt=gtk --disable-dssi --disable-plugin
> --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre
> --with-cpu=generic --host=x86_64-redhat-linux
> Thread model: posix
> gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)

I have also just encountered this build error, but am currently on the
fence as to whether it is a compiler bug in 4.1.2 or bad code.  Using
newer compilers causes the complaint to go away.  I would certainly like
to hope that compat_handle_ok() is correct, and does appear to be
correct from code inspection.

The if statement becomes gigantic after preprocessing, and I ran out of
effort today to sanitise the preprocessed output and check it for
correctness.  (At the very least, it would be kind to the compiler to
factor out the paging_mode_external(current->domain) check and degrade
the compat_handle_okay()s to compat_array_access_ok())

~Andrew

Re: 4.4.0-rc2 tagged

[Jan Beulich]

>>> On 15.01.14 at 01:09, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
> On 14/01/2014 22:49, Don Slutz wrote:
>> On 01/14/14 11:29, Ian Campbell wrote:
>>> We've just tagged 4.4.0-rc2, please test and report bugs.
>>>
>>> The tarball can be downloaded here:
>>>
>>> http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz 
>>>
>>> Ian.
>>>
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xen.org 
>>> http://lists.xen.org/xen-devel 
>>
>> This tarball does not build on CentOS 5.10:
>>
>>
>> gcc -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing
>> -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement
>> -I/home/don/xen-4.4.0-rc2/xen/include
>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-generic
>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-default
>> -msoft-float -fno-stack-protector -fno-exceptions -Wnested-externs
>> -DHAVE_GAS_VMX -mno-red-zone -mno-sse -fpic
>> -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE
>> -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith
>> -pipe -g -D__XEN__ -include
>> /home/don/xen-4.4.0-rc2/xen/include/xen/config.h -nostdinc
>> -iwithprefix include -fno-optimize-sibling-calls -DVERBOSE -DHAS_ACPI
>> -DHAS_GDBSX -DHAS_PASSTHROUGH -DHAS_PCI -DHAS_IOPORTS
>> -fno-omit-frame-pointer -DCONFIG_FRAME_POINTER -MMD -MF .memory.o.d -c
>> memory.c -o memory.o
>> cc1: warnings being treated as errors
>> memory.c: In function 'compat_memory_op':
>> memory.c:213: warning: comparison is always true due to limited range
>> of data type
>> memory.c:214: warning: comparison is always true due to limited range
>> of data type
>> memory.c:215: warning: comparison is always true due to limited range
>> of data type
>> make[5]: *** [memory.o] Error 1
>> make[5]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common/compat'
>> make[4]: *** [compat/built_in.o] Error 2
>> make[4]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common'
>> make[3]: *** [/home/don/xen-4.4.0-rc2/xen/common/built_in.o] Error 2
>> make[3]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/arch/x86'
>> make[2]: *** [/home/don/xen-4.4.0-rc2/xen/xen] Error 2
>> make[2]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>> make[1]: *** [install] Error 2
>> make[1]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>> make: *** [install-xen] Error 2
>> dcs-xen-53:~/xen-4.4.0-rc2>uname -a
>> Linux dcs-xen-53 2.6.18-371.el5xen #1 SMP Tue Oct 1 09:15:30 EDT 2013
>> x86_64 x86_64 x86_64 GNU/Linux
>> dcs-xen-53:~/xen-4.4.0-rc2>cat /etc/redhat-release
>> CentOS release 5.10 (Final)
>> dcs-xen-53:~/xen-4.4.0-rc2>gcc -v
>> Using built-in specs.
>> Target: x86_64-redhat-linux
>> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
>> --infodir=/usr/share/info --enable-shared --enable-threads=posix
>> --enable-checking=release --with-system-zlib --enable-__cxa_atexit
>> --disable-libunwind-exceptions --enable-libgcj-multifile
>> --enable-languages=c,c++,objc,obj-c++,java,fortran,ada
>> --enable-java-awt=gtk --disable-dssi --disable-plugin
>> --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre
>> --with-cpu=generic --host=x86_64-redhat-linux
>> Thread model: posix
>> gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)
> 
> I have also just encountered this build error, but am currently on the
> fence as to whether it is a compiler bug in 4.1.2 or bad code.  Using
> newer compilers causes the complaint to go away.  I would certainly like
> to hope that compat_handle_ok() is correct, and does appear to be
> correct from code inspection.
> 
> The if statement becomes gigantic after preprocessing, and I ran out of
> effort today to sanitise the preprocessed output and check it for
> correctness.  (At the very least, it would be kind to the compiler to
> factor out the paging_mode_external(current->domain) check and degrade
> the compat_handle_okay()s to compat_array_access_ok())

It's not that bad; breaking the if() up a little got me to quickly
see that this is due to struct xen_add_to_physmap_batch's
size field being uint16_t. Using a separate local variable to
latch the structure value makes the problem go away. The
warning isn't really a compiler bug, but also not very useful.

Question now is: Should we replace the checks with
BUILD_BUG_ON()s (I wouldn't want to drop them altogether)
or suppress the warning via intermediate variable?

Jan

Re: 4.4.0-rc2 tagged

[Jan Beulich]

>>> On 15.01.14 at 10:44, "Jan Beulich" <JBeulich@suse.com> wrote:
>>>> On 15.01.14 at 01:09, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> On 14/01/2014 22:49, Don Slutz wrote:
>>> On 01/14/14 11:29, Ian Campbell wrote:
>>>> We've just tagged 4.4.0-rc2, please test and report bugs.
>>>>
>>>> The tarball can be downloaded here:
>>>>
>>>> http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz 
>>>>
>>>> Ian.
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xen.org 
>>>> http://lists.xen.org/xen-devel 
>>>
>>> This tarball does not build on CentOS 5.10:
>>>
>>>
>>> gcc -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing
>>> -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement
>>> -I/home/don/xen-4.4.0-rc2/xen/include
>>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-generic
>>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-default
>>> -msoft-float -fno-stack-protector -fno-exceptions -Wnested-externs
>>> -DHAVE_GAS_VMX -mno-red-zone -mno-sse -fpic
>>> -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE
>>> -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith
>>> -pipe -g -D__XEN__ -include
>>> /home/don/xen-4.4.0-rc2/xen/include/xen/config.h -nostdinc
>>> -iwithprefix include -fno-optimize-sibling-calls -DVERBOSE -DHAS_ACPI
>>> -DHAS_GDBSX -DHAS_PASSTHROUGH -DHAS_PCI -DHAS_IOPORTS
>>> -fno-omit-frame-pointer -DCONFIG_FRAME_POINTER -MMD -MF .memory.o.d -c
>>> memory.c -o memory.o
>>> cc1: warnings being treated as errors
>>> memory.c: In function 'compat_memory_op':
>>> memory.c:213: warning: comparison is always true due to limited range
>>> of data type
>>> memory.c:214: warning: comparison is always true due to limited range
>>> of data type
>>> memory.c:215: warning: comparison is always true due to limited range
>>> of data type
>>> make[5]: *** [memory.o] Error 1
>>> make[5]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common/compat'
>>> make[4]: *** [compat/built_in.o] Error 2
>>> make[4]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common'
>>> make[3]: *** [/home/don/xen-4.4.0-rc2/xen/common/built_in.o] Error 2
>>> make[3]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/arch/x86'
>>> make[2]: *** [/home/don/xen-4.4.0-rc2/xen/xen] Error 2
>>> make[2]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>>> make[1]: *** [install] Error 2
>>> make[1]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>>> make: *** [install-xen] Error 2
>>> dcs-xen-53:~/xen-4.4.0-rc2>uname -a
>>> Linux dcs-xen-53 2.6.18-371.el5xen #1 SMP Tue Oct 1 09:15:30 EDT 2013
>>> x86_64 x86_64 x86_64 GNU/Linux
>>> dcs-xen-53:~/xen-4.4.0-rc2>cat /etc/redhat-release
>>> CentOS release 5.10 (Final)
>>> dcs-xen-53:~/xen-4.4.0-rc2>gcc -v
>>> Using built-in specs.
>>> Target: x86_64-redhat-linux
>>> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
>>> --infodir=/usr/share/info --enable-shared --enable-threads=posix
>>> --enable-checking=release --with-system-zlib --enable-__cxa_atexit
>>> --disable-libunwind-exceptions --enable-libgcj-multifile
>>> --enable-languages=c,c++,objc,obj-c++,java,fortran,ada
>>> --enable-java-awt=gtk --disable-dssi --disable-plugin
>>> --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre
>>> --with-cpu=generic --host=x86_64-redhat-linux
>>> Thread model: posix
>>> gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)
>> 
>> I have also just encountered this build error, but am currently on the
>> fence as to whether it is a compiler bug in 4.1.2 or bad code.  Using
>> newer compilers causes the complaint to go away.  I would certainly like
>> to hope that compat_handle_ok() is correct, and does appear to be
>> correct from code inspection.
>> 
>> The if statement becomes gigantic after preprocessing, and I ran out of
>> effort today to sanitise the preprocessed output and check it for
>> correctness.  (At the very least, it would be kind to the compiler to
>> factor out the paging_mode_external(current->domain) check and degrade
>> the compat_handle_okay()s to compat_array_access_ok())
> 
> It's not that bad; breaking the if() up a little got me to quickly
> see that this is due to struct xen_add_to_physmap_batch's
> size field being uint16_t. Using a separate local variable to
> latch the structure value makes the problem go away. The
> warning isn't really a compiler bug, but also not very useful.
> 
> Question now is: Should we replace the checks with
> BUILD_BUG_ON()s (I wouldn't want to drop them altogether)
> or suppress the warning via intermediate variable?

And looking at the implications I'm much in favor of using
an intermediate variable (see below).

Jan

compat/memory: fix build with old gcc

struct xen_add_to_physmap_batch's size field being uint16_t causes old
compiler versions to warn about the pointless range check done inside
compat_handle_okay().

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/compat/memory.c
+++ b/xen/common/compat/memory.c
@@ -206,18 +206,20 @@ int compat_memory_op(unsigned int cmd, X
         {
             unsigned int limit = (COMPAT_ARG_XLAT_SIZE - sizeof(*nat.atpb))
                                  / (sizeof(nat.atpb->idxs.p) + sizeof(nat.atpb->gpfns.p));
+            /* Use an intermediate variable to suppress warnings on old gcc: */
+            unsigned int size = cmp.atpb.size;
             xen_ulong_t *idxs = (void *)(nat.atpb + 1);
             xen_pfn_t *gpfns = (void *)(idxs + limit);
 
             if ( copy_from_guest(&cmp.atpb, compat, 1) ||
-                 !compat_handle_okay(cmp.atpb.idxs, cmp.atpb.size) ||
-                 !compat_handle_okay(cmp.atpb.gpfns, cmp.atpb.size) ||
-                 !compat_handle_okay(cmp.atpb.errs, cmp.atpb.size) )
+                 !compat_handle_okay(cmp.atpb.idxs, size) ||
+                 !compat_handle_okay(cmp.atpb.gpfns, size) ||
+                 !compat_handle_okay(cmp.atpb.errs, size) )
                 return -EFAULT;
 
             end_extent = start_extent + limit;
-            if ( end_extent > cmp.atpb.size )
-                end_extent = cmp.atpb.size;
+            if ( end_extent > size )
+                end_extent = size;
 
             idxs -= start_extent;
             gpfns -= start_extent;

Re: 4.4.0-rc2 tagged

[Andrew Cooper]

On 15/01/14 10:12, Jan Beulich wrote:
>>>> On 15.01.14 at 10:44, "Jan Beulich" <JBeulich@suse.com> wrote:
>>>>> On 15.01.14 at 01:09, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>> On 14/01/2014 22:49, Don Slutz wrote:
>>>> On 01/14/14 11:29, Ian Campbell wrote:
>>>>> We've just tagged 4.4.0-rc2, please test and report bugs.
>>>>>
>>>>> The tarball can be downloaded here:
>>>>>
>>>>> http://bits.xensource.com/oss-xen/release/4.4.0-rc2/xen-4.4.0-rc2.tar.gz 
>>>>>
>>>>> Ian.
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Xen-devel mailing list
>>>>> Xen-devel@lists.xen.org 
>>>>> http://lists.xen.org/xen-devel 
>>>> This tarball does not build on CentOS 5.10:
>>>>
>>>>
>>>> gcc -O1 -fno-omit-frame-pointer -m64 -g -fno-strict-aliasing
>>>> -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement
>>>> -I/home/don/xen-4.4.0-rc2/xen/include
>>>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-generic
>>>> -I/home/don/xen-4.4.0-rc2/xen/include/asm-x86/mach-default
>>>> -msoft-float -fno-stack-protector -fno-exceptions -Wnested-externs
>>>> -DHAVE_GAS_VMX -mno-red-zone -mno-sse -fpic
>>>> -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE
>>>> -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith
>>>> -pipe -g -D__XEN__ -include
>>>> /home/don/xen-4.4.0-rc2/xen/include/xen/config.h -nostdinc
>>>> -iwithprefix include -fno-optimize-sibling-calls -DVERBOSE -DHAS_ACPI
>>>> -DHAS_GDBSX -DHAS_PASSTHROUGH -DHAS_PCI -DHAS_IOPORTS
>>>> -fno-omit-frame-pointer -DCONFIG_FRAME_POINTER -MMD -MF .memory.o.d -c
>>>> memory.c -o memory.o
>>>> cc1: warnings being treated as errors
>>>> memory.c: In function 'compat_memory_op':
>>>> memory.c:213: warning: comparison is always true due to limited range
>>>> of data type
>>>> memory.c:214: warning: comparison is always true due to limited range
>>>> of data type
>>>> memory.c:215: warning: comparison is always true due to limited range
>>>> of data type
>>>> make[5]: *** [memory.o] Error 1
>>>> make[5]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common/compat'
>>>> make[4]: *** [compat/built_in.o] Error 2
>>>> make[4]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/common'
>>>> make[3]: *** [/home/don/xen-4.4.0-rc2/xen/common/built_in.o] Error 2
>>>> make[3]: Leaving directory `/home/don/xen-4.4.0-rc2/xen/arch/x86'
>>>> make[2]: *** [/home/don/xen-4.4.0-rc2/xen/xen] Error 2
>>>> make[2]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>>>> make[1]: *** [install] Error 2
>>>> make[1]: Leaving directory `/home/don/xen-4.4.0-rc2/xen'
>>>> make: *** [install-xen] Error 2
>>>> dcs-xen-53:~/xen-4.4.0-rc2>uname -a
>>>> Linux dcs-xen-53 2.6.18-371.el5xen #1 SMP Tue Oct 1 09:15:30 EDT 2013
>>>> x86_64 x86_64 x86_64 GNU/Linux
>>>> dcs-xen-53:~/xen-4.4.0-rc2>cat /etc/redhat-release
>>>> CentOS release 5.10 (Final)
>>>> dcs-xen-53:~/xen-4.4.0-rc2>gcc -v
>>>> Using built-in specs.
>>>> Target: x86_64-redhat-linux
>>>> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
>>>> --infodir=/usr/share/info --enable-shared --enable-threads=posix
>>>> --enable-checking=release --with-system-zlib --enable-__cxa_atexit
>>>> --disable-libunwind-exceptions --enable-libgcj-multifile
>>>> --enable-languages=c,c++,objc,obj-c++,java,fortran,ada
>>>> --enable-java-awt=gtk --disable-dssi --disable-plugin
>>>> --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre
>>>> --with-cpu=generic --host=x86_64-redhat-linux
>>>> Thread model: posix
>>>> gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)
>>> I have also just encountered this build error, but am currently on the
>>> fence as to whether it is a compiler bug in 4.1.2 or bad code.  Using
>>> newer compilers causes the complaint to go away.  I would certainly like
>>> to hope that compat_handle_ok() is correct, and does appear to be
>>> correct from code inspection.
>>>
>>> The if statement becomes gigantic after preprocessing, and I ran out of
>>> effort today to sanitise the preprocessed output and check it for
>>> correctness.  (At the very least, it would be kind to the compiler to
>>> factor out the paging_mode_external(current->domain) check and degrade
>>> the compat_handle_okay()s to compat_array_access_ok())
>> It's not that bad; breaking the if() up a little got me to quickly
>> see that this is due to struct xen_add_to_physmap_batch's
>> size field being uint16_t. Using a separate local variable to
>> latch the structure value makes the problem go away. The
>> warning isn't really a compiler bug, but also not very useful.
>>
>> Question now is: Should we replace the checks with
>> BUILD_BUG_ON()s (I wouldn't want to drop them altogether)
>> or suppress the warning via intermediate variable?
> And looking at the implications I'm much in favor of using
> an intermediate variable (see below).
>
> Jan
>
> compat/memory: fix build with old gcc
>
> struct xen_add_to_physmap_batch's size field being uint16_t causes old
> compiler versions to warn about the pointless range check done inside
> compat_handle_okay().
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>

>
> --- a/xen/common/compat/memory.c
> +++ b/xen/common/compat/memory.c
> @@ -206,18 +206,20 @@ int compat_memory_op(unsigned int cmd, X
>          {
>              unsigned int limit = (COMPAT_ARG_XLAT_SIZE - sizeof(*nat.atpb))
>                                   / (sizeof(nat.atpb->idxs.p) + sizeof(nat.atpb->gpfns.p));
> +            /* Use an intermediate variable to suppress warnings on old gcc: */
> +            unsigned int size = cmp.atpb.size;
>              xen_ulong_t *idxs = (void *)(nat.atpb + 1);
>              xen_pfn_t *gpfns = (void *)(idxs + limit);
>  
>              if ( copy_from_guest(&cmp.atpb, compat, 1) ||
> -                 !compat_handle_okay(cmp.atpb.idxs, cmp.atpb.size) ||
> -                 !compat_handle_okay(cmp.atpb.gpfns, cmp.atpb.size) ||
> -                 !compat_handle_okay(cmp.atpb.errs, cmp.atpb.size) )
> +                 !compat_handle_okay(cmp.atpb.idxs, size) ||
> +                 !compat_handle_okay(cmp.atpb.gpfns, size) ||
> +                 !compat_handle_okay(cmp.atpb.errs, size) )
>                  return -EFAULT;
>  
>              end_extent = start_extent + limit;
> -            if ( end_extent > cmp.atpb.size )
> -                end_extent = cmp.atpb.size;
> +            if ( end_extent > size )
> +                end_extent = size;
>  
>              idxs -= start_extent;
>              gpfns -= start_extent;
>
>
>
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