Re: [PATCH] kvm-unit-tests: Fix GCC's 4.8 labels as values for nVMX tests.

[Paolo Bonzini <pbonzini@redhat.com>]

Il 24/02/2014 16:58, Jan Kiszka ha scritto:
> On 2014-02-24 16:25, Marius Vlad wrote:
>> Commit 3b1274463fa8d074dd3bc77efe25b59a4ddd491e uses GCCs extension
>> labels as values to handle exceptions, but GCC 4.8 ``mistakingly''
>> uses the next body function as a jump label, for functions which
>> do not return. Fixed by returning a int value for those functions.
>>
>> See http://thread.gmane.org/gmane.comp.emulators.kvm.devel/119186
>>
>> Signed-off-by: Marius Vlad <mv@sec.uni-passau.de>
>> ---
>>  x86/vmx.c | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/x86/vmx.c b/x86/vmx.c
>> index fe950e6..0c895af 100644
>> --- a/x86/vmx.c
>> +++ b/x86/vmx.c
>> @@ -548,7 +548,7 @@ static void exception_handler(struct ex_regs *regs)
>>  	regs->rip = (u64)exception_return;
>>  }
>>
>> -static int test_for_exception(unsigned int ex, void (*func)(void))
>> +static int test_for_exception(unsigned int ex, int (*func)(void))
>>  {
>>  	handle_exception(ex, exception_handler);
>>  	exception = false;
>> @@ -557,23 +557,23 @@ static int test_for_exception(unsigned int ex, void (*func)(void))
>>  	return exception;
>>  }
>>
>> -static void do_vmxon_off(void)
>> +static int do_vmxon_off(void)
>>  {
>>  	exception_return = &&resume;
>>  	barrier();
>>  	vmx_on();
>>  	vmx_off();
>>  resume:
>> -	return;
>> +	return 0;
>>  }
>>
>> -static void do_write_feature_control(void)
>> +static int do_write_feature_control(void)
>>  {
>>  	exception_return = &&resume;
>>  	barrier();
>>  	wrmsr(MSR_IA32_FEATURE_CONTROL, 0);
>>  resume:
>> -	return;
>> +	return 0;
>>  }
>>
>>  static int test_vmx_feature_control(void)
>>
>
> Argh, getting old. I remembered that issue but forgot that I already had
> a fix for this queued:
>
> http://thread.gmane.org/gmane.comp.emulators.kvm.devel/117866
>
> I don't mind which version to pick, but maybe Paolo has mine already in
> his queue.

Yeah (I hadn't, but now I have).  According to GCC developers this is 
invalid code.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28581

Perhaps we should rewrite this using something more similar to "normal" 
C setjmp/longjmp.

Paolo