Re: [coreboot] Loading Linux payloads on RISC-V

[Patrick Rudolph]

Can you make use of the uImage/FIT [1] mechanism coreboot supports ?
It just needs some architecture specific code.

Can you provide a ling to the Linux calling conventions for riscv ?

[1] https://doc.coreboot.org/lib/payloads/fit.html

Regards,
Patrick
On 2018-09-23 04:59 PM, ron minnich wrote:
> ah sorry I forgot.
>
> I think selfboot could be reworked (and should be) to interpret "0" as
> "somewhere useful"?
>
> On Sat, Sep 22, 2018 at 10:47 PM ron minnich 
> wrote:
> > shouldn't we fix the riscv kernel build process? it's producing bad
> > elf files?
> >
> > On Sat, Sep 22, 2018 at 4:40 PM Jonathan Neuschäfer
> >  wrote:
> > > Hi,
> > >
> > > we've discussed this briefly at OSFC: Linux's ELF file (vmlinux)
> > > currently has segments starting at 0x0 (if you look at the
> > > physical
> > > address field) and an entry point at 0xffffffe000000000:
> > > > $ readelf -l vmlinux
> > > >
> > > > Elf file type is EXEC (Executable file)
> > > > Entry point 0xffffffe000000000
> > > > There are 3 program headers, starting at offset 64
> > > >
> > > > Program Headers:
> > > > Type           Offset             VirtAddr           PhysAddr
> > > > FileSiz            MemSiz              Flags
> > >
> > > Align
> > > > LOAD           0x0000000000001000 0xffffffe000000000
> > >
> > > 0x0000000000000000
> > > > 0x000000000000ffce 0x000000000000ffce  R E
> > >
> > > 0x1000
> > > > LOAD           0x0000000000011000 0xffffffe000010000
> > >
> > > 0x0000000000010000
> > > > 0x00000000002cda3c 0x00000000002cda3c  RWE
> > >
> > > 0x1000
> > > > NOTE           0x00000000002dea00 0xffffffe0002dda00
> > >
> > > 0x00000000002dda00
> > > > 0x000000000000003c 0x000000000000003c  R
> > >
> > > 0x4
> > > > Section to Segment mapping:
> > > > Segment Sections...
> > > > 00     .init.text
> > > > 01     .init.data .exit.text .data..percpu .text
> > >
> > > .softirqentry.text .rodata __param __modver .srodata .data
> > > __bug_table .sdata .bss __ex_table .notes
> > > > 02     .notes
> > >
> > > coreboot's SELF loader rightly points out that 0x0 is not in RAM:
> > > > Loading segment from ROM address 0x00000000200287b8
> > > > code (compression=0)
> > > > New segment dstaddr 0x0 memsize 0xffce srcaddr 0x2002880c
> > >
> > > filesize 0xffce
> > > > Loading segment from ROM address 0x00000000200287d4
> > > > code (compression=0)
> > > > New segment dstaddr 0x10000 memsize 0x2cda3c srcaddr
> > >
> > > 0x200387da filesize 0x2cda3c
> > > > Loading segment from ROM address 0x00000000200287f0
> > > > Entry Point 0xffffffe000000000
> > > > SELF Payload doesn't target RAM:
> > > > Failed Segment: 0x0, 65486 bytes
> > > > 0. 0000000080000000-0000000080011fff: RAMSTAGE
> > > > 0000000080012000-000000008003ffff: RAM
> > > > 0000000080040000-0000000080044fff: RAMSTAGE
> > > > 0000000080045000-00000000fffdbfff: RAM
> > > > 00000000fffdc000-00000000ffffffff: CONFIGURATION TABLES
> > > > 0000000100000000-000000027fffffff: RAM
> > > >
> > > > Payload not loaded.
> > >
> > > How should we solve this?
> > >
> > > One option I see is to keep CONFIG_PAYLOAD_ELF as is, and add
> > > quirks to
> > > CONFIG_PAYLOAD_LINUX.
> > >
> > > Jonathan

Loading Linux payloads on RISC-V

[Jonathan Neuschäfer]

On Sun, Sep 23, 2018 at 06:42:14PM +0200, Patrick Rudolph wrote:
> Can you make use of the uImage/FIT [1] mechanism coreboot supports ?
> It just needs some architecture specific code.

Good idea. I've seen the FIT support patches and I think FIT looks
reasonable, at least for loading Linux.

Would FIT support require discussion/cooperation with other projects
like Linux or u-boot?
> Can you provide a ling to the Linux calling conventions for riscv ?

I think a document like https://www.kernel.org/doc/Documentation/arm/Booting
hasn't been written yet for RISC-V. It's something like this:

- Linux starts in Supervisor Mode, but in physical address space, and
  expects a working Supervisor Binary Interface[0]
- register a0: hart ID
- register a1: pointer to FDT

Jonathan

[0]: https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.md

Loading Linux payloads on RISC-V

[Philipp Hug]

Am Di., 25. Sep. 2018 um 13:50 Uhr schrieb Jonathan Neuschäfer <
[e-mail]>:
> Would FIT support require discussion/cooperation with other projects
> like Linux or u-boot?
>
> What seems to be missing is the kernel image format to be used within the

FIT. e.g. look at arm64:
https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/head.S#L73
https://github.com/coreboot/coreboot/blob/master/src/arch/arm64/fit_payload....

Philipp