linux64: list linux_support.s explicitly

[emaste]

Summary

Previously we relied on the .s.o rule in share/mk/bsd.suffixes.mk to tell make that linux_support.o is built from linux_support.s, even though we do not use the .s.o rule to assemble it.

[emaste]

Adding @sjg to confirm my understanding of how linux_support.o is being built today.

I want to remove the .s.o rule from bsd.suffixes.mk (D35859) but the build failed on linux_support.o.

[dchagin]

Why linux64 only? linux also uses this rule

[emaste]

In D35864#814319, @dchagin wrote:

Why linux64 only? linux also uses this rule

I see linux_support only in linux64?

[emaste]

also specify linux_support.s explicitly - ${IMPSRC} is not defined for explicit rules

[emaste]

sys/modules/linux64/Makefile

79

I suppose ${.IMPSRC} was defined via the .s.o rule in bsd.suffixes.mk even though this rule here is not a suffix-transformation rule.

.IMPSRC   In suffix-transformation rules, the name/path of the
          source from which the target is to be transformed (the
          “implied” source); also known as ‘<’.  It is not defined
          in explicit rules.

[dchagin]

In D35864#814363, @emaste wrote:

In D35864#814319, @dchagin wrote:

Why linux64 only? linux also uses this rule

I see linux_support only in linux64?

ah, grep linux${SFX}_support.o :)

[emaste]

use full path

[emaste]

Add linux${SFX}_support.s

[emaste]

sys/modules/linux64/Makefile

79

I'll defer to @sjg for comment on the canonical way to handle this. I believe what's in this review now is workable, but perhaps it could be ${ALLSRC:[1]}? Or perhaps we should in fact have a .s.o suffix rule with no commands, and leave linux/Makefile and linux64/Makefile as is?

[emaste]

sys/modules/linux64/Makefile

79

Or yet another option, we could rename the handful of .s files affected by this review to .S.

[dchagin]

sys/modules/linux64/Makefile

79

or to .asm? like linux_locore.asm

[jrtc27]

Why not have a .s.o rule that uses Clang like we do for .S.o? I think this is conflating "we don't want to use AS directly" with "we don't want non-preprocessed assembly files".

[jrtc27]

Though this one really should be .S given it wants preprocessing

[emaste]

sys/modules/linux64/Makefile

79

Ah, I think that would work too.

.s.o:
        ${AS} ${AFLAGS} -o ${.TARGET} ${.IMPSRC}
        ${CTFCONVERT_CMD}

.S.o:
        ${CC:N${CCACHE_BIN}} ${CFLAGS} ${ACFLAGS} -c ${.IMPSRC} -o ${.TARGET}
        ${CTFCONVERT_CMD}

.asm.o:
        ${CC:N${CCACHE_BIN}} -x assembler-with-cpp ${CFLAGS} ${ACFLAGS} -c ${.IMPSRC} \
            -o ${.TARGET}
        ${CTFCONVERT_CMD}

so .asm and .S are mostly equivalent except that .asm invokes the compiler with -x assembler-with-cpp for the implicit rule.

[jrtc27]

sys/modules/linux64/Makefile

79

Yes, because -x assembler-with-cpp is automatically used for .S files

[sjg]

Sorry a bit late to the party.
First off; If you add -DWITH_META_MODE to your build, you can look at linux_support.o.meta to see exactly what was done.
If you kldload filemon you can even confirm all the files used.

As man page says .IMPSRC is only guaranteed in suffix ruels.

[sjg]

sys/modules/linux/Makefile

107 ↗

(On Diff #108366)

This ends up being very fragile. ${.ALLSRC:M*.s} would be far simpler

[sjg]

I expect .asm is handled the same as .S for the benefit of case insensitive file systems (Apple)

[emaste]

Use .ALLSRC as suggested by @sjg

[emaste]

I think this change is an improvement, independent of D35908.

[emaste]

Why not have a .s.o rule that uses Clang like we do for .S.o?

Ah, just the .S.o rule but with -x assembler instead of -x assembler-with-cpp? Yeah, that makes sense.

[ehem_freebsd_m5p.com]

I suggest D35908 should go in first, as both Makefile rules would need adjustment in D35908 if D35864 goes in first. Whereas if second, D35864 could go in with .S in both places.

[emaste]

I needed to change to :M*.s:u because linux_support.s ended up appearing twice - presumably once from the .s.o rule and once from the explicit mention in the two Makefiles. Is this expected Make behaviour?

sys/modules/linux64/Makefile

79

oops lost -o here, have restored it locally