Re: [kvm-unit-tests PATCH 08/14] powerpc/ppc64: add HV putchar

[Andrew Jones <drjones@redhat.com>]

On Tue, Aug 04, 2015 at 01:50:39PM +1000, David Gibson wrote:
> On Mon, Aug 03, 2015 at 04:41:25PM +0200, Andrew Jones wrote:
> > Add the hvcall for putchar and use it in puts. That, along with a
> > couple more lines in start to prepare for C code, and a branch to
> > main(), gets us "hello world". Run with
> > 
> > qemu-system-ppc64 -M pseries            \
> >         -bios powerpc/boot_rom.bin      \
> >         -display none -serial stdio     \
> >         -kernel powerpc/selftest.elf
> > 
> > (We're still not relocating yet, that comes in a later patch. Thus,
> >  testing hello-world at this point requires a hacked QEMU and linking
> >  the unit test at QEMU's kernel load address.)
> > 
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> >  lib/powerpc/io.c        | 15 +++++++++++++--
> >  powerpc/Makefile.common |  1 +
> >  powerpc/cstart64.S      | 27 +++++++++++++++++++++++++++
> >  3 files changed, 41 insertions(+), 2 deletions(-)
> > 
> > diff --git a/lib/powerpc/io.c b/lib/powerpc/io.c
> > index cf3b6347e1e46..a7eaafeca9205 100644
> > --- a/lib/powerpc/io.c
> > +++ b/lib/powerpc/io.c
> > @@ -6,15 +6,26 @@
> >   * This work is licensed under the terms of the GNU LGPL, version 2.
> >   */
> >  #include <libcflat.h>
> > +#include <asm/spinlock.h>
> > +
> > +extern void halt(int code);
> > +extern void putchar(int c);
> > +
> > +static struct spinlock uart_lock;
> >  
> >  void io_init(void)
> >  {
> >  }
> >  
> > -void puts(const char *s __unused)
> > +void puts(const char *s)
> >  {
> > +	spin_lock(&uart_lock);
> > +	while (*s)
> > +		putchar(*s++);
> > +	spin_unlock(&uart_lock);
> >  }
> >  
> > -void exit(int code __unused)
> > +void exit(int code)
> >  {
> > +	halt(code);
> >  }
> > diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> > index 5cd3ea8085038..d6356540918a5 100644
> > --- a/powerpc/Makefile.common
> > +++ b/powerpc/Makefile.common
> > @@ -26,6 +26,7 @@ CFLAGS += -ffreestanding
> >  CFLAGS += -Wextra
> >  CFLAGS += -O2
> >  CFLAGS += -I lib -I lib/libfdt
> > +CFLAGS += -Wa,-mregnames
> >  
> >  asm-offsets = lib/$(ARCH)/asm-offsets.h
> >  include scripts/asm-offsets.mak
> > diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> > index d9b77f44f9e0e..d7c51cd352ee4 100644
> > --- a/powerpc/cstart64.S
> > +++ b/powerpc/cstart64.S
> > @@ -6,14 +6,41 @@
> >   * This work is licensed under the terms of the GNU LGPL, version 2.
> >   */
> >  
> > +#define HVSC			.long 0x44000022
> 
> Unless your assembler is really old, you could probably use "sc 1"
> inline, instead of this macro.  Not that it really matters.

It makes sense to switch to sc for a new project. I'll do that.

> 
> > +#define H_PUT_TERM_CHAR		0x58
> > +
> > +#define LOAD_REG_IMMEDIATE(reg,expr)		\
> > +	lis	reg,(expr)@highest;		\
> > +	ori	reg,reg,(expr)@higher;		\
> > +	rldicr	reg,reg,32,31;			\
> > +	oris	reg,reg,(expr)@h;		\
> > +	ori	reg,reg,(expr)@l;
> > +
> > +#define LOAD_REG_ADDR(reg,name)			\
> > +	ld	reg,name@got(r2)
> > +
> >  .section .init
> >  
> >  .globl start
> >  start:
> > +	LOAD_REG_IMMEDIATE(r1, stackptr)
> > +	LOAD_REG_IMMEDIATE(r2, tocptr)
> > +	bl	.main
> > +	bl	.exit
> 
> Is this built for ppc64 or ppc64le?  IIUC under the new ABI version
> usually used on ppc64le, function descriptors are no longer used.  And
> even under the old ABI, I think the assembler now has the smarts to
> avoid explicitly referencing the .-symbols.

For now only building for ppc64, but eventually both. I'll remove the
dots.

Thanks,
drew

> 
> >  	b	halt
> >  
> >  .text
> > +.align 3
> >  
> >  .globl halt
> >  halt:
> >  1:	b	1b
> > +
> > +.globl putchar
> > +putchar:
> > +	sldi	r6, r3, 56
> > +	li	r3, H_PUT_TERM_CHAR
> > +	li	r4, 0	/* vty-reg 0 means to use the default vty */
> > +	li	r5, 1	/* sending just 1 byte */
> > +	HVSC
> > +	blr
> 
> -- 
> David Gibson			| I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
> 				| _way_ _around_!
> http://www.ozlabs.org/~dgibson