Date: Wed, 20 Nov 2013 16:43:52 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Marcel Moolenaar <xcllnt@mac.com> Cc: powerpc@freebsd.org, Warner Losh <imp@bsdimp.com> Subject: Re: RFC: compiler options to control what gets built and how Message-ID: <CAJ-VmokSMVyo2Tad4jcz1XT%2BEfW=MzKy4X9Zd0i7RiDk3eYuZw@mail.gmail.com> In-Reply-To: <3D481595-1F61-4244-838F-5C13ABCB830D@mac.com> References: <3D481595-1F61-4244-838F-5C13ABCB830D@mac.com>
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.. kernel modules generally need opt_xxx.h in order to correctly build with things like debug flags. net80211 for example changes the calling ABI depending upon whether IEEE80211_DEBUG is enabled or not. -adrian On 20 November 2013 09:08, Marcel Moolenaar <xcllnt@mac.com> wrote: > All, > > Background: > Juniper is refocussing efforts towards PowerPC again. Primarily > what this means for Juniper is that a select set of PowerPC- > based Juniper products will migrate to the latest FreeBSD as > the base OS underneath Junos. > What this means for FreeBSD is that Juniper will be contributing > a bunch of goodies :-) > > Problem at hand: > Juniper builds kernel modules without any reference to a kernel > configuration. This works great for architectures like x86, but > for PowerPC, MIPS and ARM this isn't always that easy. The problem > as far as I can see it is that we use kernel configurations to > indicate for which CPU we're compiling. Let's call this the > build setting for arguments sake. > > Complication: > Many embedded CPU architectures have specific compiler behaviour > you may have to tell the compiler for what CPU or ABI you're > compiling. Let's call this the compiler setting. Having both a > build setting and a compiler setting is, well, complicating. > > What I'd like to change is that we use compiler settings more > than build settings, for where it's applicable of course and as > a first stab, do it for PowerPC only. If it's successful then > it should be fairly easy to apply to ARM and MIPS. > > Examples: > 1. A compiler that generates 64-bit code can be assumed to > compiler a 64-bit PowerPC kernel. There is no need to have > a build option (like machine powerpc powerpc). Testing for > __LP64__ or something like that will do just fine. > 2. The difference between AIM and Book-E is (can) be handled > by checking the appropriate compiler defines (__embedded__) > and have us do the right thing in the kernel for modules > and for user space. > > Particular use case: > 1. Cross-tools aren't necessarily helped by the magical and > automatic selection of appropriate definitions. This is not > a problem that is in search of a solution though. Our ELF > headers handle this adequately and the same scheme can work > for things like trap frames and the likes. > 2. The remote kernel debugger stub needs different register > definitions for Book-E and AIM. These register definitions > are controller by the compiler options used, yet our stub > uses build settings. This has previously resulted in an > inability to debug the kernel remotely due to a mismatch. > 3. The buildbot I setup at Juniper builds a LINT kernel for > each CPU architecture. For PowerPC this adds an avoidable > complication that we actually need to use a different LINT > kernel configuration for no other reach than that we need > "machine powerpc powerpc64" > rather than > "machine powerpc powerpc" > A distinction that is almost entirely unnecessary. > > What needs to change to make this work: > 1. Since config(8) is the tool we use to pick up source files, > and we use the abovementioned build options to select the > right source files, we need a way to inject compiler defines > into the process of configuring the kernel build. > 2. We need well-defined built-in compiler defines for building > AIM vs. Book-E and 32-bit vs 64-bit. > > What do people think of using the compiler to drive more of what > and how we built so that the right thing happens with fewer > manual setup? > > -- > Marcel Moolenaar > xcllnt@mac.com > > > > _______________________________________________ > freebsd-ppc@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ppc > To unsubscribe, send any mail to "freebsd-ppc-unsubscribe@freebsd.org"
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