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

[David Gibson <david@gibson.dropbear.id.au>]

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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.

> +#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.

>  	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

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