Re: [PATCH] RISC-V: Add an Image header that boot loader can parse.

[Karsten Merker]

On Wed, May 01, 2019 at 09:54:43PM +0200, Karsten Merker wrote:
> On Wed, May 01, 2019 at 10:41:52PM +0530, Anup Patel wrote:
> > On Wed, May 1, 2019 at 10:30 PM Mark Rutland <mark.rutland@xxxxxxx> wrote:
> > > On Mon, Apr 29, 2019 at 10:42:40PM -0700, Atish Patra wrote:
> > > > On 4/29/19 4:40 PM, Palmer Dabbelt wrote:
> > > > > On Tue, 23 Apr 2019 16:25:06 PDT (-0700), atish.patra@xxxxxxx wrote:

> Probably I'm missing something obvious, but I cannot completely
> follow you here. My understanding is as follows:
[...]
> If the first byte in a PE/COFF header has to be an ASCII "M",
> that is 01001101 in binary.  RISC-V is little-endian and the last
> two bits of the lowest-value byte define the type of instruction. 
> According to the chapter "Base Instruction-Length Encoding" in
> the RISC-V ISA spec everything except 11 as the lowest bits
> denotes a compressed instruction and if I have puzzeled together
> the the various instruction bits correctly, ASCII "MZ" would be
> excuted as a compressed load immediate to x9/s1, wouldn't it?

Sorry, I have misinterpreted a bitfield in the spec, it's indeed
a compressed load immediate to x20/s4.

Regards,
Karsten
-- 
Ich widerspreche hiermit ausdrÃcklich der Nutzung sowie der
Weitergabe meiner personenbezogenen Daten fÃr Zwecke der Werbung
sowie der Markt- oder Meinungsforschung.