Date: Sat, 10 Mar 2018 23:46:07 +0100 From: Martin Lucina <martin@lucina.net> To: Fabian Freyer <fabian.freyer@physik.tu-berlin.de> Cc: rumpkernel-users@freelists.org, freebsd-virtualization@freebsd.org Subject: Re: rumpkernel and bhyve: triple faults Message-ID: <20180310224607.wscuqebheq5bjxww@nodbug.lucina.net> In-Reply-To: <A3574A92-0514-44AE-BE20-6BFDAE803407@physik.tu-berlin.de> References: <C49D0E56-10A4-49D8-A843-E371395831B5@physik.tu-berlin.de> <A3574A92-0514-44AE-BE20-6BFDAE803407@physik.tu-berlin.de>
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Hi, On Friday, 09.03.2018 at 18:45, Fabian Freyer wrote: > On 6 Mar 2018, at 7:45, Fabian Freyer wrote: > > Tracking down bios_crtc_base, I find that it’s loaded in > > rumprun/platform/hw/arch/amd64/locore.S:70: > > > > /* save BIOS data area values */ > > movw BIOS_COM1_BASE, %bx > > movw %bx, bios_com1_base > > movw BIOS_CRTC_BASE, %bx > > movw %bx, bios_crtc_base > > > > Where BIOS_CRTC_BASE is 0x463 and BIOS_COM1_BASE is 0x400. Checking the bhyve > > device node in /dev/vmm with xxd(1), I find the words at these addresses to be > > Uninitialised: > > > > 00000400: 0000 .. > > 00000483: 0000 .. > > > > I’m not sure where to go from here. Is this a bug in bhyve(4), should these > > values be initialised somehow, or should I patch rumpkernel(7) to skip this check > > when running on bhyve(4)? You probably want to use a serial console rather than VGA on bhyve in any case, so you'll want to add the appropriate checks to hypervisor.c and cons.c. > I’ve chased this bug down a bit further to what I believe is an issue with the > rumprun toolchain I am building on FreeBSD with the misc/rumprun port [1]. > > objdump -t helloer-rumprun.elf list a number of symbols in the *COM* section, which > holds unallocated C external variables [2]: > > objdump -t helloer-rumprun.elf | grep \*COM\* > 00000001 l O *COM* 00000001 pic1mask > 00000004 l O *COM* 00000004 pgalloc_totalkb > 00000004 l O *COM* 00000004 pgalloc_usedkb > 00001000 l O *COM* 00000020 multiboot_cmdline > 00000002 l O *COM* 00000002 bios_crtc_base > 00000001 l O *COM* 00000001 pic2mask > 00000002 l O *COM* 00000002 bios_com1_base > > As the pagetable in pagetable.s maps the first page as non-present, accessing any > of these will result in a fault. I’m pretty sure that these shouldn’t be undefined. > > A build on Linux (which boots fine) shows these not to be uninitialised: > 00000000003e3480 g O .bss 0000000000000002 bios_com1_base > 00000000003e44a0 g O .bss 0000000000000002 bios_crtc_base When you write "which boots fine", I presume you're referring to booting on bhyve? > Further down the rabbit hole, this goes on in rumprun.o: > > On Linux, bios_crtc_base is not a local symbol: > 0000000000000002 O *COM* 0000000000000002 bios_crtc_base > 0000000000000002 O *COM* 0000000000000002 bios_com1_base > > While on FreeBSD, they are marked as local: > 0000000000000002 l O *COM* 0000000000000002 bios_crtc_base > 0000000000000002 l O *COM* 0000000000000002 bios_com1_base That seems wrong. Can you try and force the toolchain to use the more recent GNU ld from devel/binutils and see if that fixes the problem? -mato
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