sparse breakage (x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu)

sparse breakage (x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu)

[Alexey Dobriyan]

Andi, with new vDSO code sparse fails to check with usual invocation here:

	$ make C=2 CF="-Wno-decl -Wno-shadow -Wno-context -D__CHECK_ENDIAN__"
		...
	  CHECK   arch/x86_64/vdso/vclock_gettime.c
	arch/x86_64/vdso/vclock_gettime.c:51:11: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:47:28: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:48:20: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:49:21: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:38:14: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:39:25: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:80:11: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:75:28: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:76:14: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:77:12: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:78:15: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:79:13: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:87:6: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:102:6: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:111:4: error: expected structure or union
	arch/x86_64/vdso/vclock_gettime.c:111:4: error: expected structure or union
	  CC      arch/x86_64/vdso/vclock_gettime.o
	cc1: error: unrecognized command line option "-Wno-decl"
	cc1: error: unrecognized command line option "-Wno-context"
	make[2]: *** [arch/x86_64/vdso/vclock_gettime.o] Error 1
	make[1]: *** [arch/x86_64/vdso] Error 2
	make: *** [_all] Error 2

Re: sparse breakage (x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu)

[Al Viro]

On Sun, Jul 22, 2007 at 08:08:09PM +0400, Alexey Dobriyan wrote:
> Andi, with new vDSO code sparse fails to check with usual invocation here:

Fucks with CF and not in a good way...

CF := $(PROFILING) -mcmodel=small -fPIC -g0 -O2 -fasynchronous-unwind-tables -m64

$(obj)/vclock_gettime.o: CFLAGS = $(CF)
$(obj)/vgetcpu.o: CFLAGS = $(CF)

s/CF/CCF/ in there (arch/x86_64/vdso/Makefile) fixes gcc problems; sparse
ones remain and I'll look into that when I get some sleep (26 hours uptime
right now).  I think I have a good idea of what's going on there, but
I'd rather not touch that code until tonight.

For now just rename the variable in makefile (obviously the right thing
to do) and that will give you sparse runs not aborted at that point.

Re: sparse breakage (x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu)

[Al Viro]

On Sun, Jul 22, 2007 at 06:06:57PM +0100, Al Viro wrote:
> On Sun, Jul 22, 2007 at 08:08:09PM +0400, Alexey Dobriyan wrote:
> > Andi, with new vDSO code sparse fails to check with usual invocation here:
> 
> Fucks with CF and not in a good way...
> 
> CF := $(PROFILING) -mcmodel=small -fPIC -g0 -O2 -fasynchronous-unwind-tables -m64
> 
> $(obj)/vclock_gettime.o: CFLAGS = $(CF)
> $(obj)/vgetcpu.o: CFLAGS = $(CF)
> 
> s/CF/CCF/ in there (arch/x86_64/vdso/Makefile) fixes gcc problems; sparse
> ones remain and I'll look into that when I get some sleep (26 hours uptime
> right now).  I think I have a good idea of what's going on there, but
> I'd rather not touch that code until tonight.
> 
> For now just rename the variable in makefile (obviously the right thing
> to do) and that will give you sparse runs not aborted at that point.

Actually,

ed evaluate.c <<EOF
/evaluate_member_dereference
/examine_symbol_type/m/ctype =
w
q
EOF

ought to take care of sparse, AFAICS.  IOW, in evaluate_member_dereference()
we need to do examine_symbol_type(ctype) before checking ctype->type, etc.
As it is, we end up with SYM_TYPEOF node there and it's not expanded until
we'd checked if we have SYM_STRUCT.  We would, after expansion, but we don't
do it until too late.

I haven't checked if that's causes any regressions, but it looks
straightforward enough to be a plausible fix.  I won't test it until
tonight, though (see above).  Minimal testcase is
struct foo {int x;} v;
typeof(v) *p;
void bar(void)
{
        p->x = 0;
}
and any serious regression testing should get both the sparse tests and
comparing kernel builds with and without that fix...