Re: [Xen-devel] [PATCH] x86: fix clang .macro retention check

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Nov 14, 2019 at 04:56:35PM +0100, Jan Beulich wrote:
> On 14.11.2019 14:12, Roger Pau Monné  wrote:
> > On Thu, Nov 14, 2019 at 12:43:33PM +0100, Jan Beulich wrote:
> >> On 14.11.2019 10:38, Roger Pau Monné  wrote:
> >>> On Wed, Nov 13, 2019 at 06:01:40PM +0100, Jan Beulich wrote:
> >>>> --- a/xen/arch/x86/Rules.mk
> >>>> +++ b/xen/arch/x86/Rules.mk
> >>>> @@ -82,6 +64,6 @@ $(call as-option-add,CFLAGS,CC,".include
> >>>>  # Check whether clang keeps .macro-s between asm()-s:
> >>>>  # https://bugs.llvm.org/show_bug.cgi?id=36110
> >>>>  $(call as-option-add,CFLAGS,CC,\
> >>>> -                     ".macro FOO\n.endm\"); asm volatile (\".macro 
> >>>> FOO\n.endm",\
> >>>> +                     ".macro FOO\n.endm"$$(close); asm volatile 
> >>>> $$(open)".macro FOO\n.endm",\
> >>>
> >>> Thanks, while here could you also replace the '\n' with a ';'? '\n'
> >>> doesn't work properly and gives me the following error:
> >>>
> >>> <stdin>:1:32: error: missing terminating '"' character 
> >>> [-Werror,-Winvalid-pp-token]
> >>> void _(void) { asm volatile (  ".macro FOO
> >>>                                ^
> >>> <stdin>:1:32: error: expected string literal in 'asm'
> >>> <stdin>:3:6: error: missing terminating '"' character 
> >>> [-Werror,-Winvalid-pp-token]
> >>> .endm" ); }
> >>>      ^
> >>> <stdin>:3:12: error: expected ')'
> >>> .endm" ); }
> >>>            ^
> >>> <stdin>:1:29: note: to match this '('
> >>> void _(void) { asm volatile (  ".macro FOO
> >>>                             ^
> >>> <stdin>:3:12: error: expected '}'
> >>> .endm" ); }
> >>>            ^
> >>> <stdin>:1:14: note: to match this '{'
> >>> void _(void) { asm volatile (  ".macro FOO
> >>>              ^
> >>
> >> So this must be yet another issue - I did specifically look at the what
> >> gets handed to the compiler, and I did not see the above. I wonder
> >> whether that's also related to the \" that I found necessary to drop -
> >> with what you say I'd expect the un-escaped double quotes won't work
> >> for you.
> > 
> > AFAIK those work fine.
> > 
> >> I suppose though this un-escaping (or not) happens at a level
> >> other than the compiler, i.e. either a difference in shell or in make
> >> behavior.
> > 
> > Maybe, I'm not an expert on shells or makefiles. This time I've tested
> > with Debian 9.5 instead of FreeBSD, so it's likely that what was there
> > worked fine on FreeBSD which I'm quite sure was what I testing against
> > back when I added this check.
> > 
> > This is what I used to test:
> > 
> > GNU Make 4.1
> > GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu)
> > 
> > Not sure whether there are other utilities involved in this behavior.
> > 
> >> IOW I don't think just replacing \n by ; will do.
> > 
> > I can give your patch a try with FreeBSD, but that's not going to
> > explain the different behavior I'm afraid.
> 
> Let's approach this a different way. Below is a debugging patch
> (similar to something I did use yesterday). With my patch and yours
> on top (but with the \n restored for the purposes here, and with
> the block inserted first in the ifeq(,) it gets moved to) I get in
> .as-insn.1
> 
> void _(void) { asm volatile ( ".equ \"x\",1" ); }
> void _(void) { asm volatile ( ".L0:\n.L1:\n.skip (.L1 - .L0)" ); }
> void _(void) { asm volatile ( ".include \"asm/indirect_thunk_asm.h\"" ); }
> void _(void) { asm volatile (  ".macro FOO\n.endm"); asm volatile (".macro 
> FOO\n.endm" ); }

The following data is from Debian GNU/Linux 9.5 (stretch), I haven't
tried on FreeBSD but this output is already different from what you
get.

So this is what I have in .as-insn.1 (the relevant part):

void _(void) { asm volatile ( ".equ \"x\",1" ); }
void _(void) { asm volatile ( "invpcid (%rax),%rax" ); }
void _(void) { asm volatile (  ".if ((1 > 0) < 0); .error \"\";.endif" ); }
void _(void) { asm volatile (  ".L1: .L2: .nops (.L2 - .L1),9" ); }
void _(void) { asm volatile ( ".L0:
.L1:
.skip (.L1 - .L0)" ); }
void _(void) { asm volatile ( ".include \"asm/indirect_thunk_asm.h\"" ); }
void _(void) { asm volatile (  ".macro FOO
.endm"); asm volatile (".macro FOO
.endm" ); }

So my make/shell/whatever is expanding the \n.

FTR the command I've used is `make -j8 xen clang=y CC=clang-8`.

> 
> (you may see further lines here, as the context in which I ran into
> this was a patch to move out the determination of -DHAVE_AS_*, which
> also is in effect here) and in .as-insn.2
> 
> <stdin>:1:44: error: invalid number of bytes
> void _(void) { asm volatile ( ".L0:\n.L1:\n.skip (.L1 - .L0)" ); }
>                                            ^
> <inline asm>:3:7: note: instantiated into assembly here
> .skip (.L1 - .L0)
>       ^
> 1 error generated.
> /tmp/--8f887d.s: Assembler messages:
> /tmp/--8f887d.s:20: Error: Macro `foo' was already defined
> clang-5.0.1: error: assembler command failed with exit code 1 (use -v to see 
> invocation)

And in .as-insn.2:

<stdin>:1:32: error:
void _(void) { asm volatile (  ".if ((1 > 0) < 0); .error \"\";.endif" ); }
                               ^
<inline asm>:1:21: note: instantiated into assembly here
        .if ((1 > 0) < 0); .error "";.endif
                           ^
1 error generated.
<stdin>:1:32: error: unknown directive
void _(void) { asm volatile (  ".L1: .L2: .nops (.L2 - .L1),9" ); }
                               ^
<inline asm>:1:12: note: instantiated into assembly here
        .L1: .L2: .nops (.L2 - .L1),9
                  ^
1 error generated.
<stdin>:1:31: error: missing terminating '"' character 
[-Werror,-Winvalid-pp-token]
void _(void) { asm volatile ( ".L0:
                              ^
<stdin>:1:31: error: expected string literal in 'asm'
<stdin>:3:18: error: missing terminating '"' character 
[-Werror,-Winvalid-pp-token]
.skip (.L1 - .L0)" ); }
                 ^
<stdin>:3:24: error: expected ')'
.skip (.L1 - .L0)" ); }
                       ^
<stdin>:1:29: note: to match this '('
void _(void) { asm volatile ( ".L0:
                            ^
<stdin>:3:24: error: expected '}'
.skip (.L1 - .L0)" ); }
                       ^
<stdin>:1:14: note: to match this '{'
void _(void) { asm volatile ( ".L0:
             ^
5 errors generated.
<stdin>:1:32: error: missing terminating '"' character 
[-Werror,-Winvalid-pp-token]
void _(void) { asm volatile (  ".macro FOO
                               ^
<stdin>:1:32: error: expected string literal in 'asm'
<stdin>:3:6: error: missing terminating '"' character 
[-Werror,-Winvalid-pp-token]
.endm" ); }
     ^
<stdin>:3:12: error: expected ')'
.endm" ); }
           ^
<stdin>:1:29: note: to match this '('
void _(void) { asm volatile (  ".macro FOO
                            ^
<stdin>:3:12: error: expected '}'
.endm" ); }
           ^
<stdin>:1:14: note: to match this '{'
void _(void) { asm volatile (  ".macro FOO
             ^
5 errors generated.

Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel